The thermodynamic and elastic properties of magnesium silicate （MgSiO3） perovskite at high pressure are investigated with the quasi-harmonic Debye model and the first-principles method based on the density functiona...The thermodynamic and elastic properties of magnesium silicate （MgSiO3） perovskite at high pressure are investigated with the quasi-harmonic Debye model and the first-principles method based on the density functional theory. The obtained equation of state is consistent with the available experimental data. The heat capacity and the thermal expansion coefficient agree with the observed values and other calculations at high pressures and temperatures. The elastic constants are calculated using the finite strain method. A complete elastic tensor of MgSiO3 perovskite is determined in the wide pressure range. The geologically important quantities： Young＇s modulus, Poisson＇s ratio, Debye temperature, and crystal anisotropy, are derived from the calculated data.展开更多
In this paper the stability constants and thermodynamic parameters for complexes of rare earth elements with L-threonine have been measured systematically by potentiometry and calorimetry at 25℃ and ionic strength of...In this paper the stability constants and thermodynamic parameters for complexes of rare earth elements with L-threonine have been measured systematically by potentiometry and calorimetry at 25℃ and ionic strength of 0.15 mol/L(NaCl).The thermodynamic values for protonation of the anion of L-threonine have been obtained.The dependence of stability,enthalpy and entropy change of the complex upon atomic number of cation is investigated,and the coordination of L-threonine to rare earth is also discussed in detail.展开更多
The structure optimization and frequency calculation have been carried out at the B3LYP/6-31G＊ level towards herbicidal monosulfuron using density functional theory.The computed results showed that the intramolecular...The structure optimization and frequency calculation have been carried out at the B3LYP/6-31G＊ level towards herbicidal monosulfuron using density functional theory.The computed results showed that the intramolecular hydrogen bond N-H…N can stabilize the molecule.IR spectra,Raman spectra and thermodynamic properties under different temperatures were also obtained.The first vertical excited state electronic transition energy was calculated by time-dependent density function theory,and absorption wavelength of the lowest energy excitation was obtained at 339.59 nm,belonging to the near UV.These results provided the basis for studies on compound＇s structure-activity relationship.展开更多
The thermodynamic properties of Mg Ca Si and its mother phase Ca2 Si are comparatively investigated from ab initio calculations and quasi-harmonic Debye-Grüneisen model. At 0 K, Mg Ca Si is more thermodynamically...The thermodynamic properties of Mg Ca Si and its mother phase Ca2 Si are comparatively investigated from ab initio calculations and quasi-harmonic Debye-Grüneisen model. At 0 K, Mg Ca Si is more thermodynamically stable. Under high temperature, the advantage of higher thermodynamically stability of Mg Ca Si is reduced, originating from the less negative entropy contribution because the thermodynamic entropy of Mg Ca Si increases more slowly with temperature and the entropy values are slightly smaller.With increasing temperature, the anti-softening ability for Mg Ca Si is slightly smaller due to the slightly faster decrease trend of bulk modulus than that of Ca2 Si, although the bulk modulus of Mg Ca Si is higher in the whole temperature range considered. The thermal expansion behaviors of both Mg Ca Si and Ca_(2)Si exhibit similar increase trend, although thermal expansion coefficient of MgCaSi is slightly lower and the increases is slightly slower at lower temperature. The isochoric heat capacity CVand isobaric heat capacity CPof MgCaSi and Ca_(2)Si rise nonlinearly with temperature, and both CVare close to the Dulong–Petit limit at high temperature due to the negligibly small electronic contribution. The Debye temperature of both phases decrease with increasing temperature, and the downtrend for Mg Ca Si is slightly faster.However, MgCaSi possess slightly higher Debye temperature, implying the stronger chemical bonds and higher thermal conductivity than the mother phase Ca_(2)Si. The Grüneisen parameter of MgCaSi and Ca_(2)Si increase slightly with temperature, the values of MgCaSi are slightly larger. The investigation of electronic structures shows that with substitution of partial Ca by Mg in Ca_(2)Si, the stronger MgASi,MgACa and SiASi covalent bonds are formed, and plays a very significant role for the structural stability and mechanical properties.展开更多
As a new addition to lightweight composite structures,the sandwich cylindrical shell with a metallic wire mesh core has emerged as a promising solution for thermodynamic performance analysis at elevated temperatures.T...As a new addition to lightweight composite structures,the sandwich cylindrical shell with a metallic wire mesh core has emerged as a promising solution for thermodynamic performance analysis at elevated temperatures.The intricate interwoven cellular formations within the metallic wire mesh pose difficulties for thermo-mechanical modeling and property evaluation.First,the constitutive models employed to characterize hysteresis phenomena were presented,comprising isotropic elasticity,Bergstrom-Boyce model,Ogden hyper-elasticity,and parameter identification through mechanical examinations at varying temperatures.Second,the finite element modeling of cylindrical shell structures was determined for modal and steady-state dynamic analyses.Third,the experimental procedures were carried out,including the preparation of the sandwich cylindrical shell and the dynamic testing platform.The first-order natural frequency of the cylindrical shell structure is close to the resonance frequency of the dynamic test results,with a maximum error of 6.5%,demonstrating the accuracy of the simulation model.When compared to the solid-core cylindrical shell,the average insertion loss of the sandwich cylindrical shell structure within the frequency range of 10–1000 Hz at room temperature is up to 11.09 dB.Furthermore,at elevated temperatures,the average insertion loss of the sandwich cylindrical shell decreases but fluctuates as the temperature changes.展开更多
(NbZrHfTi)C high-entropy ceramics,as an emerging class of ultra-high-temperature materials,have garnered significant interest due to their unique multi-principal-element crystal structure and exceptional hightemperatu...(NbZrHfTi)C high-entropy ceramics,as an emerging class of ultra-high-temperature materials,have garnered significant interest due to their unique multi-principal-element crystal structure and exceptional hightemperature properties.This study systematically investigates the mechanical properties of(NbZrHfTi)C high-entropy ceramics by employing first-principles density functional theory,combined with the Debye-Grüneisen model,to explore the variations in their thermophysical properties with temperature(0–2000 K)and pressure(0–30 GPa).Thermodynamically,the calculated mixing enthalpy and Gibbs free energy confirm the feasibility of forming a stable single-phase solid solution in(NbZrHfTi)C.The calculated results of the elastic stiffness constant indicate that the material meets the mechanical stability criteria of the cubic crystal system,further confirming the structural stability.Through evaluation of key mechanical parameters—bulk modulus,shear modulus,Young’s modulus,and Poisson’s ratio—we provide comprehensive insight into the macro-mechanical behaviour of the material and its correlation with the underlying microstructure.Notably,compared to traditional binary carbides and their average properties,(NbZrHfTi)C exhibits higher Vickers hardness(Approximately 28.5 GPa)and fracture toughness(Approximately 3.4 MPa⋅m^(1/2)),which can be primarily attributed to the lattice distortion and solid-solution strengthening mechanism.The study also utilizes the quasi-harmonic approximation method to predict the material’s thermophysical properties,including Debye temperature(initial value around 563 K),thermal expansion coefficient(approximately 8.9×10^(−6) K−1 at 2000 K),and other key parameters such as heat capacity at constant volume.The results show that within the studied pressure and temperature ranges,(NbZrHfTi)C consistently maintains a stable phase structure and good thermomechanical properties.The thermal expansion coefficient increasing with temperature,while heat capacity approaches the Dulong-Petit limit at elevated temperatures.These findings underscore the potential of(NbZrHfTi)C applications in ultra-high temperature thermal protection systems,cutting tool coatings,and nuclear structural materials.展开更多
With the theory of statistical physics dealing with chemical reaction (the law of mass action), the different thermodynamic property of noble gases (mono-atomic gases) in a small bubble and diatomic gases in a small b...With the theory of statistical physics dealing with chemical reaction (the law of mass action), the different thermodynamic property of noble gases (mono-atomic gases) in a small bubble and diatomic gases in a small bubble semi-quantitatively are analyzed. As bubbles of the mono-atomic and the diatomic gases are compressed, shock waves are produced in both bubbles. Though shock wave leads to sharp increase of pressure and temperature of gases in the bubble, diatomic gas will excitated vibrations and dissociate themselves to mono-atomic gas, these processes will consume many accumulated heat energy and block the further increase of the temperature. Therefore, compare with the mono-atomic gases in the bubble, there will be no enough charged particles ionized to flash for diatomic gases in the bubble, this may be the reason why a bubble of diatomic gases has no single bubble sonoluminescence while a bubble of noble gases has.展开更多
Complete optimization was conducted for 136 polybromo-phenoxathiin congeners（PBPTs） on the B3LYP/6-31G＊ level with Gaussian 03 program.The structural parameters and thermodynamical parameters of each molecule were ...Complete optimization was conducted for 136 polybromo-phenoxathiin congeners（PBPTs） on the B3LYP/6-31G＊ level with Gaussian 03 program.The structural parameters and thermodynamical parameters of each molecule were obtained under the standard state of 298.15 K and 1.013×10^5 Pa.Reverse linear regression was employed to establish the quantitative structure-property correlation models between heat capacity at constant volume（CVθ）,entropy（Sθ）,standard heat of formation（△fHθ） and standard free energy of formation（△fGθ） of PBPTs and the structural parameters（the most negative atomic charge（q^-） and molecular average polarizability（α））.These models presented better correlations（r^2〉0.97）.And they were validated by variance inflation factor（VIF） and t-test,which can better explain the regularity of thermodynamical property of PBPTs,and has good stability and great prediction ability.展开更多
The mechanical and thermodynamic properties of W-Ti alloys(including W_(15)Ti_(1),W_(14)Ti_(2),W_(12)Ti_(4) and W_(8)Ti_(8) alloys)were investigated by the first-principles approach based on density functional theory....The mechanical and thermodynamic properties of W-Ti alloys(including W_(15)Ti_(1),W_(14)Ti_(2),W_(12)Ti_(4) and W_(8)Ti_(8) alloys)were investigated by the first-principles approach based on density functional theory.The results indicate that W-Ti alloys except W_(8)Ti_(8) are thermodynamically stable.The modulus and hardness of W-Ti alloys are smaller than those of pure tungsten and gradually decrease with increasing Ti concentration.However,their B/G ratios and Poisson's ratios exceed those of pure tungsten,suggesting that the introduction of Ti decreases the mechanical strength while enhancing the ductility of W-Ti alloys.The thermal expansion coefficients for W-Ti alloys all surpass those of pure tungsten,indicating that the introduction of titanium exacerbates the thermal expansion behavior of W-Ti alloys.Nevertheless,elevated pressure has the capacity to suppress the thermal expansion tendencies in titanium-doped tungsten alloys.This study offers theoretical insights for the design of nuclear materials by exploring the mechanical and thermodynamic properties of W-Ti alloys.展开更多
Density(p),speed of sound(u),viscosity(η),and refractive index(n_(D))were measured for pure acetonitrile,trichloroethene,and tetrachloroethene,as well as their binary mixtures at temperatures T=(293.15,298.15,303.15)...Density(p),speed of sound(u),viscosity(η),and refractive index(n_(D))were measured for pure acetonitrile,trichloroethene,and tetrachloroethene,as well as their binary mixtures at temperatures T=(293.15,298.15,303.15)K and at ambient pressure(81.5 kPa).From the experimental data,excess molar volume(V_(m)~E),thermal expansion coefficients(α),deviations in isentropic compressibility(Δκ_(S)),viscosity(Δ_η),and refractive index(Δn_(D))were calculated.These values were then correlated using the Redlich-Kister polynomial equation,with fitting coefficients and standard deviations determined.Additionally,the Prigogine-Flory-Patterson(PFP)theory and the Extended Real Associated Solution(ERAS)model were employed to correlate the excess molar volume,while the Perturbed Chain Statistical Associating Fluid Theory(PC-SAFT)was used to predict the density of mixtures.展开更多
The phase equilibria relationship of the system RbCl-PEG6000-H2O were investigated at temperatures of 288.2,298.2,and 308.2 K,the compositions of solid-liquid equilibria(SLE)and liquid-liquid equilibria(LLE)were deter...The phase equilibria relationship of the system RbCl-PEG6000-H2O were investigated at temperatures of 288.2,298.2,and 308.2 K,the compositions of solid-liquid equilibria(SLE)and liquid-liquid equilibria(LLE)were determined.The complete phase diagrams,binodal curve diagrams,and tie-line diagrams were all plotted.Results show that both solid-liquid equilibria and liquid-liquid equilibria relationships at each studied temperature.The complete phase diagrams at 288.2 K,298.2 K and 308.2 K consist of six phase regions:unsaturated liquid region(L),two saturated solutions with one solid phase of RbCl(L_S),one saturated liquid phase with two solid phases of PEG6000 and RbCl(2S+L),an aqueous two-phase region(2L),and a region with two liquids and one solid phase of RbCl(2L_S).With the increase in temperature,the layering ability of the aqueous two-phase system increases,and both regions(2L)and(2L_S)increase.The binodal curves were fitted using the nonlinear equations proposed by Mistry,Hu,and Jayapal.Additionally,the tie-line data were correlated with the Othmer-Tobias,Bancroft,Hand,and Bachman equations.The liquid-liquid equilibria at 288.2 K,298.2 K and 308.2 K were calculated using the NRTL model.The findings confirm that the experimental and calculated values are in close agreement,demonstrating the model’s effectiveness in representing the system’s behavior.展开更多
Magnesium and its compounds are recognized as favorable materials for structural uses,primarily due to their lightweight nature and remarkable specific strength.This research employed first-principles methodologies to...Magnesium and its compounds are recognized as favorable materials for structural uses,primarily due to their lightweight nature and remarkable specific strength.This research employed first-principles methodologies to investigate how pressure affects the crystal structure along with the elastic and thermodynamic characteristics of MgXY_(2)(X=Zn,Cd,and Y=Ag,Au,Cu)compounds.All analyses were implemented via the Perdew-Burke-Ernzerhof variant of the Generalized Gradient Approximation alongside a plane-wave ultrasoft pseudopotential approach.The findings on the elastic constants indicated that these MgXY_(2)compounds have maintained their stability at pressures up to 500 kBar.These constants informed detailed assessments of properties like elastic modulus,Poisson’s ratio,Vickers hardness,and material anisotropy.The Quantum Espresso software was utilized to calculate melting points,Debye temperature,and minimum thermal conductivity values.A temperature range spanning from 0 to 800 K allowed for an evaluation of vibrational energy,free energy,entropy,and specific heat capacity metrics.The anticipated physical attributes suggest significant potential for these magnesium compounds in biomedical fields.展开更多
Although the existence of glass–glass interfaces(GGIs)enables improved ductility of metallic nanoglasses(NGs),the excess free volumes at GGIs would cause the NGs to have a much-reduced mechanical strength.Herein,entr...Although the existence of glass–glass interfaces(GGIs)enables improved ductility of metallic nanoglasses(NGs),the excess free volumes at GGIs would cause the NGs to have a much-reduced mechanical strength.Herein,entropy-stabilized GGIs have been in-vestigated in Co–Fe–Ni–Zn–P NGs,which have a large entropy of mixing(1.32R,where R is the gas constant)and could be in a new glass phase,different from that of glassy grain interiors.Through quantitatively determining the activation energy of glass transition sep-arately for the GGIs and glassy grain interiors,the excess free volumes at GGIs are found to be reduced in comparison with those in the glassy grain interiors.The thermodynamically stable GGIs could be associated with increasing entropy of mixing in the GGI regions,which stabilizes the atomic structures of GGIs and enhances the glass forming ability of Co–Fe–Ni–Zn–P NGs.The influences of entropy-stabilized GGIs on the mechanical properties of Co–Fe–Ni–Zn–P NGs are further investigated by nanoindentation and creep tests under tensile deformation,demonstrating that there are notable enhancements in the ductility and mechanical strength for Co–Fe–Ni–Zn–P NGs.This work contributes to an in-depth understanding on the GGI phase in NGs and offers an alternative method for strengthening NGs through GGI engineering.展开更多
Accurate prediction of pure component physiochemical properties is crucial for process integration, multiscale modelling, and optimization. In this work, an enhanced framework for pure component property prediction by...Accurate prediction of pure component physiochemical properties is crucial for process integration, multiscale modelling, and optimization. In this work, an enhanced framework for pure component property prediction by using explainable machine learning methods is proposed. In this framework, the molecular representation method based on the connectivity matrix effectively considers atomic bonding relationships to automatically generate features. The supervised machine learning model random forest is applied for feature ranking and pooling. The adjusted R^(2) is introduced to penalize the inclusion of additional features, providing an assessment of the true contribution of features. The prediction results for normal boiling point (T_(b)), liquid molar volume (L_(mv)), critical temperature (T_(c)) and critical pressure (P_(c)) obtained using Artificial Neural Network and Gaussian Process Regression models confirm the accuracy of the molecular representation method. Comparison with GC based models shows that the root-mean-square error on the test set can be reduced by up to 83.8%. To enhance the interpretability of the model, a feature analysis method based on Shapley values is employed to determine the contribution of each feature to the property predictions. The results indicate that using the feature pooling method reduces the number of features from 13316 to 100 without compromising model accuracy. The feature analysis results for Tb, Lmv, Tc, and Pc confirms that different molecular properties are influenced by different structural features, aligning with mechanistic interpretations. In conclusion, the proposed framework is demonstrated to be feasible and provides a solid foundation for mixture component reconstruction and process integration modelling.展开更多
The effects of pressure on the structural stability,elasticity,electronic properties,and thermodynamic properties of Al,Al_(3)Cu,Al_(2)Cu,Al_(4)Cu_(9),AlCu_(3),and Cu were investigated using first-principles calculati...The effects of pressure on the structural stability,elasticity,electronic properties,and thermodynamic properties of Al,Al_(3)Cu,Al_(2)Cu,Al_(4)Cu_(9),AlCu_(3),and Cu were investigated using first-principles calculations.The experimental results indicate that the calculated equilibrium lattice constant,elastic constant,and elastic modulus agree with both theoretical and experimental data at 0 GPa.The Young's modulus,bulk modulus,and shear modulus increase with increasing pressure.The influence of pressure on mechanical properties is explained from a chemical bond perspective.By employing the quasi-harmonic approximation model of phonon calculation,the temperature and pressure dependence of thermodynamic parameters in the range of 0 to 800 K and 0 to 100 GPa are determined.The findings demonstrate that the thermal capacity and coefficient of thermal expansion increase with increasing temperature and decrease with increasing pressure.This study provides fundamental data and support for experimental investigations and further theoretical research on the properties of aluminum-copper intermetallic compounds.展开更多
The micellization behavior and thermodynamic properties of cetyltrimethylammonium bromide(CTAB)in single lithium chloride(LiCl),potassium chloride(KCl),magnesium chloride(MgCl_(2))and calcium chloride(CaCl_(2))solutio...The micellization behavior and thermodynamic properties of cetyltrimethylammonium bromide(CTAB)in single lithium chloride(LiCl),potassium chloride(KCl),magnesium chloride(MgCl_(2))and calcium chloride(CaCl_(2))solutions were investigated at 288.15318.15 K.Result showed that the critical micelle concentration(CMC)values of CTAB in all solutions decreased to a minimum value around 298.15 K and then increased with further increasing the temperature.In all cases,the CMC values decreased with increasing salt concentration at each temperature.Additionally,the introduction of any single salt resulted in a reduction of CMC values for CTAB,attributed to the combined effects of counterions and entropy-driven interactions.The observed trend for CMC values was as follows:CMCH_(2)O>CMCKCl>CMCLiCl>CMCCaCl_(2)>CMCMgCl_(2).Furthermore,standard thermodynamic parameters,including standard free energy of micellization(ΔDG_(m)^(0)),standard enthalpy of micellization(ΔDH0m)and standard entropy of micellization(DS0 m),were calculated based on the obtained CMC values.The negative values ofΔDG_(m)^(0)indicated that the formation of CTAB micelles was a spontaneous behavior.The variations inΔDH0m andΔDS_(m)^(0)suggested that micellization was primarily entropy-driven at temperatures between 288.15 and 298.15 K,while it was influenced by both entropy and enthalpy from 298.15 to 318.15 K.Fourier transform infrared spectroscopy(FTIR)and transmission electron microscope(TEM)were employed to further explore the effects of salts on the micellization behavior of CTAB.展开更多
The effects of the Rashba spin–orbit interaction and external electric and magnetic fields on the thermodynamic properties of parabolic quantum dots are investigated.An explicit partition function is derived,and ther...The effects of the Rashba spin–orbit interaction and external electric and magnetic fields on the thermodynamic properties of parabolic quantum dots are investigated.An explicit partition function is derived,and thermodynamic quantities,including specific heat,entropy,and magnetic susceptibility,are analyzed.The behavior of Shannon entropy-related thermodynamic quantities is examined under varying magnetic fields and Hamiltonian parameters through numerical analysis.The results reveal a pronounced Schottky anomaly in the heat capacity at lower temperatures.The susceptibility exhibits a progressive enhancement and transitions to higher values with changes in the quantum dot parameters.In the presence of the Rashba spin–orbit interaction,the specific heat increases with temperature,reaches a peak,and then decreases to zero.Additionally,the susceptibility increases with theβparameter for varying Rashba spin–orbit interaction coefficients,and at a fixed temperature,it further increases with the Rashba coefficient.展开更多
Mg_(2)V_(2)O_(7)is the most promising candidate for low-temperature co-fired ceramic(LTCC)multilayer devices.Selecting the appropriate precursors strongly requires reliable thermodynamic properties to be defined accur...Mg_(2)V_(2)O_(7)is the most promising candidate for low-temperature co-fired ceramic(LTCC)multilayer devices.Selecting the appropriate precursors strongly requires reliable thermodynamic properties to be defined accurately.In this study,the structural parameters of the Mg_(2)V_(2)O_(7)at ambient temperature indicate that it is crystallized in space group of P2_(1)/c.Notably,Mg_(2)V_(2)O_(7)has low lattice thermal conductivity(k_(L))of 4.77,5.12,and 4.52 W/m K,along the a,b,and c axes,respectively,which originates from the large phonon scattering rate and low phonon group velocity.The α-Mg_(2)V_(2)O_(7)←→β-Mg_(2)V_(2)O_(7) and β-Mg_(2)V_(2)O_(7)←→γ-Mg_(2)V_(2)O_(7)polymorphic transitions occur at 743℃and 908℃with enthalpy change of 1.82±0.04 kJ/mol and 1.51±0.04 kJ/mol,respectively.The endothermic effect at 1083℃ with an enthalpy change of 26.54±0.26 kJ/mol is related to the congruent melting of γ-Mg_(2)V_(2)O_(7).In addition,the molar heat capacity of Mg_(2)V_(2)O_(7) was measured utilizing drop calorimetry at high temperatures.The measured thermodynamic properties were then applied to select precursors for preparing Mg_(2)V_(2)O_(7)via a solid-state reaction,indicating that the V_(2)O_5 and Mg(OH)_(2) precursors are strongly recommended due to their thermodynamic superiority.展开更多
Based on the location of bromine substituents and conjugation matrix, a new substituent po- sition index ~X not only was defined, but also molecular shape indexes Km and electronega- tivity distance vectors Mm of diph...Based on the location of bromine substituents and conjugation matrix, a new substituent po- sition index ~X not only was defined, but also molecular shape indexes Km and electronega- tivity distance vectors Mm of diphenylamine and 209 kinds of polybrominated diphenylamine （PBDPA） molecules were calculated. Then the quantitative structure-property relationships （QSPR） among the thermodynamic properties of 210 organic pollutants and 0X, K3, M29, M36 were founded by Leaps-and-Bounds regression. Using the four structural parameters as input neurons of the artificial neural network, three satisfactory QSPR models with network structures of 4：21：1, 4：24：1, and 4：24：1 respectively, were achieved by the back-propagation algorithm. The total correlation coefficients R were 0.9999, 0.9997, and 0.9995 respectively and the standard errors S were 1.036, 1.469, and 1.510 respectively. The relative mean deviation between the predicted value and the experimental value of Sθ, AfHe and △fGθ- were 0.11%, 0.34% and 0.24% respectively, which indicated that the QSPR models had good stability and superior predictive ability. The results showed that there were good nonlinear correlations between the thermodynamic properties of PBDPAs and the four structural pa- rameters. Thus, it was concluded that the ANN models established by the new substituent position index were fully applicable to predict properties of PBDPAs.展开更多
基金This work was supported by the National Natural Science Foundation of China （No.11064007 and No.11164013）, the Natural Science Foundation of Gansu Province of China （No.1014RJZA046）, the Program for New Century Excellent Talents in University, and the Key Project of Chinese Ministry of Education （No.209127）.
文摘The thermodynamic and elastic properties of magnesium silicate （MgSiO3） perovskite at high pressure are investigated with the quasi-harmonic Debye model and the first-principles method based on the density functional theory. The obtained equation of state is consistent with the available experimental data. The heat capacity and the thermal expansion coefficient agree with the observed values and other calculations at high pressures and temperatures. The elastic constants are calculated using the finite strain method. A complete elastic tensor of MgSiO3 perovskite is determined in the wide pressure range. The geologically important quantities： Young＇s modulus, Poisson＇s ratio, Debye temperature, and crystal anisotropy, are derived from the calculated data.
基金The Project Supported by NSFC and Lab.of RE Chem.and Phys.
文摘In this paper the stability constants and thermodynamic parameters for complexes of rare earth elements with L-threonine have been measured systematically by potentiometry and calorimetry at 25℃ and ionic strength of 0.15 mol/L(NaCl).The thermodynamic values for protonation of the anion of L-threonine have been obtained.The dependence of stability,enthalpy and entropy change of the complex upon atomic number of cation is investigated,and the coordination of L-threonine to rare earth is also discussed in detail.
基金Sponsored by the Youth Foundation for Natural Science from the Sichuan Provincial Education Department (No. 07ZB080)
文摘The structure optimization and frequency calculation have been carried out at the B3LYP/6-31G＊ level towards herbicidal monosulfuron using density functional theory.The computed results showed that the intramolecular hydrogen bond N-H…N can stabilize the molecule.IR spectra,Raman spectra and thermodynamic properties under different temperatures were also obtained.The first vertical excited state electronic transition energy was calculated by time-dependent density function theory,and absorption wavelength of the lowest energy excitation was obtained at 339.59 nm,belonging to the near UV.These results provided the basis for studies on compound＇s structure-activity relationship.
基金support from Significant Project of Guangxi Scientific Foundation (2018GXNSFDA281010)National Natural Science Foundation of China (51461002)。
文摘The thermodynamic properties of Mg Ca Si and its mother phase Ca2 Si are comparatively investigated from ab initio calculations and quasi-harmonic Debye-Grüneisen model. At 0 K, Mg Ca Si is more thermodynamically stable. Under high temperature, the advantage of higher thermodynamically stability of Mg Ca Si is reduced, originating from the less negative entropy contribution because the thermodynamic entropy of Mg Ca Si increases more slowly with temperature and the entropy values are slightly smaller.With increasing temperature, the anti-softening ability for Mg Ca Si is slightly smaller due to the slightly faster decrease trend of bulk modulus than that of Ca2 Si, although the bulk modulus of Mg Ca Si is higher in the whole temperature range considered. The thermal expansion behaviors of both Mg Ca Si and Ca_(2)Si exhibit similar increase trend, although thermal expansion coefficient of MgCaSi is slightly lower and the increases is slightly slower at lower temperature. The isochoric heat capacity CVand isobaric heat capacity CPof MgCaSi and Ca_(2)Si rise nonlinearly with temperature, and both CVare close to the Dulong–Petit limit at high temperature due to the negligibly small electronic contribution. The Debye temperature of both phases decrease with increasing temperature, and the downtrend for Mg Ca Si is slightly faster.However, MgCaSi possess slightly higher Debye temperature, implying the stronger chemical bonds and higher thermal conductivity than the mother phase Ca_(2)Si. The Grüneisen parameter of MgCaSi and Ca_(2)Si increase slightly with temperature, the values of MgCaSi are slightly larger. The investigation of electronic structures shows that with substitution of partial Ca by Mg in Ca_(2)Si, the stronger MgASi,MgACa and SiASi covalent bonds are formed, and plays a very significant role for the structural stability and mechanical properties.
基金financial support by the National Natural Science Foundation of China(No.12272094)the Key Project of National Defence Innovation Zone of Science and Technology Commission of CMC,China(No.XXX-033-01)the Natural Science Foundation of Fujian Province of China(No.2022J01541)。
文摘As a new addition to lightweight composite structures,the sandwich cylindrical shell with a metallic wire mesh core has emerged as a promising solution for thermodynamic performance analysis at elevated temperatures.The intricate interwoven cellular formations within the metallic wire mesh pose difficulties for thermo-mechanical modeling and property evaluation.First,the constitutive models employed to characterize hysteresis phenomena were presented,comprising isotropic elasticity,Bergstrom-Boyce model,Ogden hyper-elasticity,and parameter identification through mechanical examinations at varying temperatures.Second,the finite element modeling of cylindrical shell structures was determined for modal and steady-state dynamic analyses.Third,the experimental procedures were carried out,including the preparation of the sandwich cylindrical shell and the dynamic testing platform.The first-order natural frequency of the cylindrical shell structure is close to the resonance frequency of the dynamic test results,with a maximum error of 6.5%,demonstrating the accuracy of the simulation model.When compared to the solid-core cylindrical shell,the average insertion loss of the sandwich cylindrical shell structure within the frequency range of 10–1000 Hz at room temperature is up to 11.09 dB.Furthermore,at elevated temperatures,the average insertion loss of the sandwich cylindrical shell decreases but fluctuates as the temperature changes.
基金supported by the National Natural Science Foundation of China(Nos.92166105 and 52005053)High-Tech Industry Science and Technology Innovation Leading Program of Hunan Province(No.2020GK2085)the Science and Technology Innovation Program of Hunan Province(No.2021RC3096).
文摘(NbZrHfTi)C high-entropy ceramics,as an emerging class of ultra-high-temperature materials,have garnered significant interest due to their unique multi-principal-element crystal structure and exceptional hightemperature properties.This study systematically investigates the mechanical properties of(NbZrHfTi)C high-entropy ceramics by employing first-principles density functional theory,combined with the Debye-Grüneisen model,to explore the variations in their thermophysical properties with temperature(0–2000 K)and pressure(0–30 GPa).Thermodynamically,the calculated mixing enthalpy and Gibbs free energy confirm the feasibility of forming a stable single-phase solid solution in(NbZrHfTi)C.The calculated results of the elastic stiffness constant indicate that the material meets the mechanical stability criteria of the cubic crystal system,further confirming the structural stability.Through evaluation of key mechanical parameters—bulk modulus,shear modulus,Young’s modulus,and Poisson’s ratio—we provide comprehensive insight into the macro-mechanical behaviour of the material and its correlation with the underlying microstructure.Notably,compared to traditional binary carbides and their average properties,(NbZrHfTi)C exhibits higher Vickers hardness(Approximately 28.5 GPa)and fracture toughness(Approximately 3.4 MPa⋅m^(1/2)),which can be primarily attributed to the lattice distortion and solid-solution strengthening mechanism.The study also utilizes the quasi-harmonic approximation method to predict the material’s thermophysical properties,including Debye temperature(initial value around 563 K),thermal expansion coefficient(approximately 8.9×10^(−6) K−1 at 2000 K),and other key parameters such as heat capacity at constant volume.The results show that within the studied pressure and temperature ranges,(NbZrHfTi)C consistently maintains a stable phase structure and good thermomechanical properties.The thermal expansion coefficient increasing with temperature,while heat capacity approaches the Dulong-Petit limit at elevated temperatures.These findings underscore the potential of(NbZrHfTi)C applications in ultra-high temperature thermal protection systems,cutting tool coatings,and nuclear structural materials.
文摘With the theory of statistical physics dealing with chemical reaction (the law of mass action), the different thermodynamic property of noble gases (mono-atomic gases) in a small bubble and diatomic gases in a small bubble semi-quantitatively are analyzed. As bubbles of the mono-atomic and the diatomic gases are compressed, shock waves are produced in both bubbles. Though shock wave leads to sharp increase of pressure and temperature of gases in the bubble, diatomic gas will excitated vibrations and dissociate themselves to mono-atomic gas, these processes will consume many accumulated heat energy and block the further increase of the temperature. Therefore, compare with the mono-atomic gases in the bubble, there will be no enough charged particles ionized to flash for diatomic gases in the bubble, this may be the reason why a bubble of diatomic gases has no single bubble sonoluminescence while a bubble of noble gases has.
基金supported by the Scientific Research Foundation of Guangxi Provincial Education Department (GJKY (2006) No 26)the Research Funds of Guangxi Key Laboratory of Environmental Engineering, Protection and Assessment (0801K007, 0801K008)
文摘Complete optimization was conducted for 136 polybromo-phenoxathiin congeners（PBPTs） on the B3LYP/6-31G＊ level with Gaussian 03 program.The structural parameters and thermodynamical parameters of each molecule were obtained under the standard state of 298.15 K and 1.013×10^5 Pa.Reverse linear regression was employed to establish the quantitative structure-property correlation models between heat capacity at constant volume（CVθ）,entropy（Sθ）,standard heat of formation（△fHθ） and standard free energy of formation（△fGθ） of PBPTs and the structural parameters（the most negative atomic charge（q^-） and molecular average polarizability（α））.These models presented better correlations（r^2〉0.97）.And they were validated by variance inflation factor（VIF） and t-test,which can better explain the regularity of thermodynamical property of PBPTs,and has good stability and great prediction ability.
基金Funded by National Key R&D Program of China(No.2021YFB3802300)the National Natural Science Foundation of China(No.52171045)the Joint Fund(No.8091B022108)。
文摘The mechanical and thermodynamic properties of W-Ti alloys(including W_(15)Ti_(1),W_(14)Ti_(2),W_(12)Ti_(4) and W_(8)Ti_(8) alloys)were investigated by the first-principles approach based on density functional theory.The results indicate that W-Ti alloys except W_(8)Ti_(8) are thermodynamically stable.The modulus and hardness of W-Ti alloys are smaller than those of pure tungsten and gradually decrease with increasing Ti concentration.However,their B/G ratios and Poisson's ratios exceed those of pure tungsten,suggesting that the introduction of Ti decreases the mechanical strength while enhancing the ductility of W-Ti alloys.The thermal expansion coefficients for W-Ti alloys all surpass those of pure tungsten,indicating that the introduction of titanium exacerbates the thermal expansion behavior of W-Ti alloys.Nevertheless,elevated pressure has the capacity to suppress the thermal expansion tendencies in titanium-doped tungsten alloys.This study offers theoretical insights for the design of nuclear materials by exploring the mechanical and thermodynamic properties of W-Ti alloys.
基金Bu-Ali Sina University for providing financial support for conducting this study。
文摘Density(p),speed of sound(u),viscosity(η),and refractive index(n_(D))were measured for pure acetonitrile,trichloroethene,and tetrachloroethene,as well as their binary mixtures at temperatures T=(293.15,298.15,303.15)K and at ambient pressure(81.5 kPa).From the experimental data,excess molar volume(V_(m)~E),thermal expansion coefficients(α),deviations in isentropic compressibility(Δκ_(S)),viscosity(Δ_η),and refractive index(Δn_(D))were calculated.These values were then correlated using the Redlich-Kister polynomial equation,with fitting coefficients and standard deviations determined.Additionally,the Prigogine-Flory-Patterson(PFP)theory and the Extended Real Associated Solution(ERAS)model were employed to correlate the excess molar volume,while the Perturbed Chain Statistical Associating Fluid Theory(PC-SAFT)was used to predict the density of mixtures.
基金supported by the National Natural Science Foundation of China(U1507111).
文摘The phase equilibria relationship of the system RbCl-PEG6000-H2O were investigated at temperatures of 288.2,298.2,and 308.2 K,the compositions of solid-liquid equilibria(SLE)and liquid-liquid equilibria(LLE)were determined.The complete phase diagrams,binodal curve diagrams,and tie-line diagrams were all plotted.Results show that both solid-liquid equilibria and liquid-liquid equilibria relationships at each studied temperature.The complete phase diagrams at 288.2 K,298.2 K and 308.2 K consist of six phase regions:unsaturated liquid region(L),two saturated solutions with one solid phase of RbCl(L_S),one saturated liquid phase with two solid phases of PEG6000 and RbCl(2S+L),an aqueous two-phase region(2L),and a region with two liquids and one solid phase of RbCl(2L_S).With the increase in temperature,the layering ability of the aqueous two-phase system increases,and both regions(2L)and(2L_S)increase.The binodal curves were fitted using the nonlinear equations proposed by Mistry,Hu,and Jayapal.Additionally,the tie-line data were correlated with the Othmer-Tobias,Bancroft,Hand,and Bachman equations.The liquid-liquid equilibria at 288.2 K,298.2 K and 308.2 K were calculated using the NRTL model.The findings confirm that the experimental and calculated values are in close agreement,demonstrating the model’s effectiveness in representing the system’s behavior.
基金support of the National Center for High Performance Computing(UHe M)#1012332022#。
文摘Magnesium and its compounds are recognized as favorable materials for structural uses,primarily due to their lightweight nature and remarkable specific strength.This research employed first-principles methodologies to investigate how pressure affects the crystal structure along with the elastic and thermodynamic characteristics of MgXY_(2)(X=Zn,Cd,and Y=Ag,Au,Cu)compounds.All analyses were implemented via the Perdew-Burke-Ernzerhof variant of the Generalized Gradient Approximation alongside a plane-wave ultrasoft pseudopotential approach.The findings on the elastic constants indicated that these MgXY_(2)compounds have maintained their stability at pressures up to 500 kBar.These constants informed detailed assessments of properties like elastic modulus,Poisson’s ratio,Vickers hardness,and material anisotropy.The Quantum Espresso software was utilized to calculate melting points,Debye temperature,and minimum thermal conductivity values.A temperature range spanning from 0 to 800 K allowed for an evaluation of vibrational energy,free energy,entropy,and specific heat capacity metrics.The anticipated physical attributes suggest significant potential for these magnesium compounds in biomedical fields.
基金This work has been endorsed by the Chengdu Guangming Paite Precious Metal Co.,Ltd.,the CDGM Glass Co.,Ltd.,China,and the Research Grants Council of Hong Kong Special Administrative Region,China(No.15233823).
文摘Although the existence of glass–glass interfaces(GGIs)enables improved ductility of metallic nanoglasses(NGs),the excess free volumes at GGIs would cause the NGs to have a much-reduced mechanical strength.Herein,entropy-stabilized GGIs have been in-vestigated in Co–Fe–Ni–Zn–P NGs,which have a large entropy of mixing(1.32R,where R is the gas constant)and could be in a new glass phase,different from that of glassy grain interiors.Through quantitatively determining the activation energy of glass transition sep-arately for the GGIs and glassy grain interiors,the excess free volumes at GGIs are found to be reduced in comparison with those in the glassy grain interiors.The thermodynamically stable GGIs could be associated with increasing entropy of mixing in the GGI regions,which stabilizes the atomic structures of GGIs and enhances the glass forming ability of Co–Fe–Ni–Zn–P NGs.The influences of entropy-stabilized GGIs on the mechanical properties of Co–Fe–Ni–Zn–P NGs are further investigated by nanoindentation and creep tests under tensile deformation,demonstrating that there are notable enhancements in the ductility and mechanical strength for Co–Fe–Ni–Zn–P NGs.This work contributes to an in-depth understanding on the GGI phase in NGs and offers an alternative method for strengthening NGs through GGI engineering.
基金support from China Scholarship Council(CSC)(202406440073).
文摘Accurate prediction of pure component physiochemical properties is crucial for process integration, multiscale modelling, and optimization. In this work, an enhanced framework for pure component property prediction by using explainable machine learning methods is proposed. In this framework, the molecular representation method based on the connectivity matrix effectively considers atomic bonding relationships to automatically generate features. The supervised machine learning model random forest is applied for feature ranking and pooling. The adjusted R^(2) is introduced to penalize the inclusion of additional features, providing an assessment of the true contribution of features. The prediction results for normal boiling point (T_(b)), liquid molar volume (L_(mv)), critical temperature (T_(c)) and critical pressure (P_(c)) obtained using Artificial Neural Network and Gaussian Process Regression models confirm the accuracy of the molecular representation method. Comparison with GC based models shows that the root-mean-square error on the test set can be reduced by up to 83.8%. To enhance the interpretability of the model, a feature analysis method based on Shapley values is employed to determine the contribution of each feature to the property predictions. The results indicate that using the feature pooling method reduces the number of features from 13316 to 100 without compromising model accuracy. The feature analysis results for Tb, Lmv, Tc, and Pc confirms that different molecular properties are influenced by different structural features, aligning with mechanistic interpretations. In conclusion, the proposed framework is demonstrated to be feasible and provides a solid foundation for mixture component reconstruction and process integration modelling.
基金Funded by the National Key R&D Program of China(No.2021YFB3802300)the Foundation of National Key Laboratory of Shock Wave and Detonation Physics(No.JCKYS2022212004)the National Natural Science Foundation of China(No.52171045),and the Joint Fund(No.8091B022108)。
文摘The effects of pressure on the structural stability,elasticity,electronic properties,and thermodynamic properties of Al,Al_(3)Cu,Al_(2)Cu,Al_(4)Cu_(9),AlCu_(3),and Cu were investigated using first-principles calculations.The experimental results indicate that the calculated equilibrium lattice constant,elastic constant,and elastic modulus agree with both theoretical and experimental data at 0 GPa.The Young's modulus,bulk modulus,and shear modulus increase with increasing pressure.The influence of pressure on mechanical properties is explained from a chemical bond perspective.By employing the quasi-harmonic approximation model of phonon calculation,the temperature and pressure dependence of thermodynamic parameters in the range of 0 to 800 K and 0 to 100 GPa are determined.The findings demonstrate that the thermal capacity and coefficient of thermal expansion increase with increasing temperature and decrease with increasing pressure.This study provides fundamental data and support for experimental investigations and further theoretical research on the properties of aluminum-copper intermetallic compounds.
基金The support of National Natural Science Foundation of China(22208198 and 22478232)is gratefully acknowledged。
文摘The micellization behavior and thermodynamic properties of cetyltrimethylammonium bromide(CTAB)in single lithium chloride(LiCl),potassium chloride(KCl),magnesium chloride(MgCl_(2))and calcium chloride(CaCl_(2))solutions were investigated at 288.15318.15 K.Result showed that the critical micelle concentration(CMC)values of CTAB in all solutions decreased to a minimum value around 298.15 K and then increased with further increasing the temperature.In all cases,the CMC values decreased with increasing salt concentration at each temperature.Additionally,the introduction of any single salt resulted in a reduction of CMC values for CTAB,attributed to the combined effects of counterions and entropy-driven interactions.The observed trend for CMC values was as follows:CMCH_(2)O>CMCKCl>CMCLiCl>CMCCaCl_(2)>CMCMgCl_(2).Furthermore,standard thermodynamic parameters,including standard free energy of micellization(ΔDG_(m)^(0)),standard enthalpy of micellization(ΔDH0m)and standard entropy of micellization(DS0 m),were calculated based on the obtained CMC values.The negative values ofΔDG_(m)^(0)indicated that the formation of CTAB micelles was a spontaneous behavior.The variations inΔDH0m andΔDS_(m)^(0)suggested that micellization was primarily entropy-driven at temperatures between 288.15 and 298.15 K,while it was influenced by both entropy and enthalpy from 298.15 to 318.15 K.Fourier transform infrared spectroscopy(FTIR)and transmission electron microscope(TEM)were employed to further explore the effects of salts on the micellization behavior of CTAB.
文摘The effects of the Rashba spin–orbit interaction and external electric and magnetic fields on the thermodynamic properties of parabolic quantum dots are investigated.An explicit partition function is derived,and thermodynamic quantities,including specific heat,entropy,and magnetic susceptibility,are analyzed.The behavior of Shannon entropy-related thermodynamic quantities is examined under varying magnetic fields and Hamiltonian parameters through numerical analysis.The results reveal a pronounced Schottky anomaly in the heat capacity at lower temperatures.The susceptibility exhibits a progressive enhancement and transitions to higher values with changes in the quantum dot parameters.In the presence of the Rashba spin–orbit interaction,the specific heat increases with temperature,reaches a peak,and then decreases to zero.Additionally,the susceptibility increases with theβparameter for varying Rashba spin–orbit interaction coefficients,and at a fixed temperature,it further increases with the Rashba coefficient.
基金supported by the National Key Research and Development Program of China(No.2022YFC3901001-1)the National Natural Science Foundation of China(Grant No.U1902217)financial support from the Chinese Scholarship Council(CSC No.202106050084)。
文摘Mg_(2)V_(2)O_(7)is the most promising candidate for low-temperature co-fired ceramic(LTCC)multilayer devices.Selecting the appropriate precursors strongly requires reliable thermodynamic properties to be defined accurately.In this study,the structural parameters of the Mg_(2)V_(2)O_(7)at ambient temperature indicate that it is crystallized in space group of P2_(1)/c.Notably,Mg_(2)V_(2)O_(7)has low lattice thermal conductivity(k_(L))of 4.77,5.12,and 4.52 W/m K,along the a,b,and c axes,respectively,which originates from the large phonon scattering rate and low phonon group velocity.The α-Mg_(2)V_(2)O_(7)←→β-Mg_(2)V_(2)O_(7) and β-Mg_(2)V_(2)O_(7)←→γ-Mg_(2)V_(2)O_(7)polymorphic transitions occur at 743℃and 908℃with enthalpy change of 1.82±0.04 kJ/mol and 1.51±0.04 kJ/mol,respectively.The endothermic effect at 1083℃ with an enthalpy change of 26.54±0.26 kJ/mol is related to the congruent melting of γ-Mg_(2)V_(2)O_(7).In addition,the molar heat capacity of Mg_(2)V_(2)O_(7) was measured utilizing drop calorimetry at high temperatures.The measured thermodynamic properties were then applied to select precursors for preparing Mg_(2)V_(2)O_(7)via a solid-state reaction,indicating that the V_(2)O_5 and Mg(OH)_(2) precursors are strongly recommended due to their thermodynamic superiority.
文摘Based on the location of bromine substituents and conjugation matrix, a new substituent po- sition index ~X not only was defined, but also molecular shape indexes Km and electronega- tivity distance vectors Mm of diphenylamine and 209 kinds of polybrominated diphenylamine （PBDPA） molecules were calculated. Then the quantitative structure-property relationships （QSPR） among the thermodynamic properties of 210 organic pollutants and 0X, K3, M29, M36 were founded by Leaps-and-Bounds regression. Using the four structural parameters as input neurons of the artificial neural network, three satisfactory QSPR models with network structures of 4：21：1, 4：24：1, and 4：24：1 respectively, were achieved by the back-propagation algorithm. The total correlation coefficients R were 0.9999, 0.9997, and 0.9995 respectively and the standard errors S were 1.036, 1.469, and 1.510 respectively. The relative mean deviation between the predicted value and the experimental value of Sθ, AfHe and △fGθ- were 0.11%, 0.34% and 0.24% respectively, which indicated that the QSPR models had good stability and superior predictive ability. The results showed that there were good nonlinear correlations between the thermodynamic properties of PBDPAs and the four structural pa- rameters. Thus, it was concluded that the ANN models established by the new substituent position index were fully applicable to predict properties of PBDPAs.
