Dielectric materials are essential in modern electronics,serving as the backbone of numerous components across a wide array of electronic devices[1,2].As technology advances,the demand for materials with high permitti...Dielectric materials are essential in modern electronics,serving as the backbone of numerous components across a wide array of electronic devices[1,2].As technology advances,the demand for materials with high permittivity,low dielectric loss,and thermal stability continues to rise.Traditional strategies to enhance permittivity often involve mechanisms such as phase transitions in ferroelectrics or interfacial polarization in boundary layer capacitor(IBLC)systems.However,each comes with trade-offs.展开更多
Devising robust S-scheme photocatalysts is of central importance for achieving high-efficient micropollu-tant decontamination.However,the conscious optimization of S-scheme system with high performance remains a prime...Devising robust S-scheme photocatalysts is of central importance for achieving high-efficient micropollu-tant decontamination.However,the conscious optimization of S-scheme system with high performance remains a prime challenge.Herein,carbon quantum dots(CDs)and Mn_(0.5)Cd_(0.5)S(MCS)are mounted on BiOBr(BOB)microspheres,establishing an advanced S-scheme heterojunction with interfacial Bi-S bond.The interfacial Bi-S bonds function as superb channels at atomic-scale to abate the energy barrier for S-scheme charge transportation.Meanwhile,CDs serve as electron collectors to preserve highly reductive electrons from MCS,further augmenting the spatial separation of photo-carriers.Therefore,the optimized CDs/MCS/BOB(MBC)heterojunction manifests significantly strengthened tetracycline hydrochloride(TC)destruction activity and its reaction rate constant is approximately 3.1,2.2,2.1,and 1.5 folds that than that of MCS,BOB,BOB/CDs and MCS/BOB.In addition,MBC exhibits high stability and significant resistance to environmental interferences.The toxicology evaluation confirms the effective abatement of toxicity of TC after treatment.This achievement demonstrates the benefits of CDs-optimized S-scheme photosystems with chemical bonds for photocatalytic water decontamination.展开更多
The electronic structures, chemical bonding and elastic properties of the tetragonal phase BiOCuS were investigated by using density-functional theory （DFT） within generalized gradient approximation （GGA）. The cal...The electronic structures, chemical bonding and elastic properties of the tetragonal phase BiOCuS were investigated by using density-functional theory （DFT） within generalized gradient approximation （GGA）. The calculated energy band structures show that the tetragonal phase BiOCuS is an indirect semiconductor with the calculated band gap of about 0.503 eV. The density of states （DOS） and the partial density of states （PDOS） calculations show that the DOS near the Fermi level is mainly from the Cu-3d state. Population analysis suggests that the chemical bonding in BiOCuS has predominantly ionic character with mixed covalent-ionic character. Basic physical properties, such as lattice constant, bulk modulus, shear modulus, elastic constants, were calculated. The elastic modulus and Poisson ratio were also predicted. The results show that tetragonal phase BiOCuS is mechanically stable and behaves in a ductile manner.展开更多
The electronic structures, chemical bonding and elastic properties of the Co2P-type structure phase ultra-incompressible Re2P （orthorhombic phase） were investigated by density-functional theory （DFT） within genera...The electronic structures, chemical bonding and elastic properties of the Co2P-type structure phase ultra-incompressible Re2P （orthorhombic phase） were investigated by density-functional theory （DFT） within generalized gradient approximation （GGA）. The calculated energy band structures show that the orthorhombic structure phase Re2P is metallic material. The density of state （DOS） and the partial density of state （PDOS） calculations show that the DOS near the Fermi level is mainly from the Re-5d state. Population analysis suggests that the chemical bonding in Re2P has predominantly covalent character with mixed covalent-ionic character. Basic physical properties, such as lattice constant, bulk modulus, shear modulus, and elastic constants Cij, were calculated. The elastic modulus and Poisson ratio were also predicted. The results show that the Co2P-type structure phase Re2P is mechanically stable and behaves in a brittle manner.展开更多
The structural parameters, chemical bonding and elastic properties of the tetragonal phase quaternary arsenide oxides YZnAsO and LaZnAsO were investigated by using density-functional theory （DFT） within generalized ...The structural parameters, chemical bonding and elastic properties of the tetragonal phase quaternary arsenide oxides YZnAsO and LaZnAsO were investigated by using density-functional theory （DFT） within generalized gradient approximation （GGA）. The GGA calculated structural parameters are in agreement with the experimental results. Population analysis suggests that the chemical bonding in YZnAsO and LaZnAsO can be classified as a mixture of ionic and covalent characteristic. Single-crystal elastic constants were calculated and the polycrystalline elastic modules were estimated according to Voigt, Reuss and Hill＇s approximations （VRH）. The result shows that both YZnAsO and LaZnAsO are relatively soft materials exhibiting ductile behavior. The calculated polycrystalline elastic anisotropy result shows that LaZnAsO is more anisotropy in compressibility and YZnAsO is more anisotropy in shear.展开更多
The relation among electronic structure, chemical bond and thermoelectric property of Ca3 Co2 O6 and Ni-doped was studied by density function theory and discrete variation method（DFT-DVM）. The results indicate that ...The relation among electronic structure, chemical bond and thermoelectric property of Ca3 Co2 O6 and Ni-doped was studied by density function theory and discrete variation method（DFT-DVM）. The results indicate that the highest valence band（ HVB ）attd the lowest conduction band（ LCB ） are mainly attribuled to Co3d, Ni3d and O2p atomic orbitals. The property of a semiconductor is shown from the gap between HVB and LCB. The gap of Ni-doped one is less than that of Ca3 Co2 O6. The non-metal bond or ceramic characteristic of Ni-doped one is weaker than that of Ca3 Co2 O6, but the metal characteristics of Ni-doped one are stronger than those of Ca3 Co2 O6. The thermoelectric property should be improved by adding Ni element into the system of Ca3 Co2 O6 .展开更多
Molecular property depends on the property, the number of the elements, and the interaction between elements(such as chemical bonds). Based on the above-mentioned idea, two methods to estimate the isobaric heat capaci...Molecular property depends on the property, the number of the elements, and the interaction between elements(such as chemical bonds). Based on the above-mentioned idea, two methods to estimate the isobaric heat capacity of liquids organic compounds were developed. Ten elements groups and 32 chemical bond groups were defined by considering the structure of organic compounds. The group contribution values and correlation parameters were regressed by the ridge regression method with the experiment data of 1137 compounds. The heat capacity can be calculated by summating the contributions of the elements and chemical bond groups. The two methods were compared with existing group contribution methods, such as Chickos, Zabransky-Ruzicka, and Zdenka Kolska. The results show that those new estimation methods' overall average relative deviations were 5.81% and 5.71%, which were lower than the other three methods. Those methods were more straightforward in compound splitting.Those new methods can be used to estimate the liquid heat capacity of silicon-containing compounds,which the other three methods cannot estimate. The new methods are more accessible, broader, and more accurate. Therefore, this research has important scientific significance and vast application prospects.展开更多
The chemical bonding nature of rare earth（RE） elements can be studied by a quantitative analysis of electron domain of an atom. The outer electrons of RE elements are within the valence shell 4f^（0-14）5d^（0-1）6s...The chemical bonding nature of rare earth（RE） elements can be studied by a quantitative analysis of electron domain of an atom. The outer electrons of RE elements are within the valence shell 4f^（0-14）5d^（0-1）6s^2, which are involved in all chemical bonding features. We in this work found that the chemical bonding characteristics of 4f electrons are a kind of hybridizations, and classified them into three types of chemical bonding of 4f^（0-14）5d^（0-1）6s^2, furthermore, the coordination number ranging from 2 to 16 could thus be determined. We selected Y（NO_3）_3, La（NO_3）_3, Ce（NO_3）_3, YCl_3, LaCl_3, and CeCl_3 as examples to in-situ observe their IR spectra of chemical bonding behaviors of Y^（3＋）, La^（3＋） and Ce^（3＋） cations, which could show different chemical bonding modes of 4f and 5d electrons. In the present study, we obtained the direct criterion to confirm whether 4f electrons can participate in chemical bonding, that is, only when the coordination number of RE cations is larger than 9.展开更多
Titanium diboride was calculated by the density function and discrete variational (DFT-DVM) method to study the relation between structure and properties.Titanium and its first-nearest boron atoms form a strong covale...Titanium diboride was calculated by the density function and discrete variational (DFT-DVM) method to study the relation between structure and properties.Titanium and its first-nearest boron atoms form a strong covalent bond,so TiB 2 has high melting point,hardness and chemical stability.Titanium atom releases two electrons to form Ti 2+ ions,and a boron atom gets one electron to come into B- ion.B- takes the sp2 hybrid and forms σ bonds to link other boron atoms in the same layer.The other one 2p z orbital of every B- ion in the same layer interacts each other to form the π molecular orbital,so TiB 2 has fine electrical property.The calculated density of state is close to the result of XPS experiment of TiB 2.Mainly Ti3d and B2p atomic orbitals contribute the total DOS near the Fermi level.展开更多
Eye trauma, decreased immunity, and contact lens wear often cause serious bacterial infections and irreversible corneal damage. To realize the responsive release of antibiotics such as gentamicin sulfate(GS), a novel ...Eye trauma, decreased immunity, and contact lens wear often cause serious bacterial infections and irreversible corneal damage. To realize the responsive release of antibiotics such as gentamicin sulfate(GS), a novel antibacterial contact lens was constructed through self-assembly of antibiotics loaded ADAGS/PEI(polyethyleneimine) multilayer films on the surface. Both in vitro and in vivo antibacterial tests demonstrated high efficient and fast antibacterial property based on the smart responsive to bacterial infections and reversible drug loading and release.展开更多
The relation among electronic structure, chemical bond and property of Ti3SiC2 and Al-doped was studied by density function and discrete variation （ DFT- DVM） method. When Al element is added into Ti3 SiC2 , there i...The relation among electronic structure, chemical bond and property of Ti3SiC2 and Al-doped was studied by density function and discrete variation （ DFT- DVM） method. When Al element is added into Ti3 SiC2 , there is a less difference of ionic bond, which does not play a leading role to influent the properties. After adding Al, the covalent bond of Al and the near Ti becomes somewhat weaker, but the covalent bond of Al and the Si in the same layer is obviously stronger than that of Si and Si before adding. Therefore, in preparation of Ti3 SiC2 , adding a proper quantity of Al can promote the formation of Ti3 SiC2 . The density of stnte shows that there is a mixed conductor character in both of Ti3 SiC2 and adding Al element. Ti3 SiC2 is with more tendencies to form a semiconductor. The total density of state near Fermi lever after adding Al is larger than that before adding, so the electric conductivity may increase after adding Al.展开更多
Calcium aluminate cement bonded corundum castable specimens were prepared using brown fused corundum （8 - 5, 5 - 3, 3 - 1 mm ） , white fused corundum （ ≤ 1, ≤0. 045 mm）, micro-sized α-Al2O3 and microsilica as s...Calcium aluminate cement bonded corundum castable specimens were prepared using brown fused corundum （8 - 5, 5 - 3, 3 - 1 mm ） , white fused corundum （ ≤ 1, ≤0. 045 mm）, micro-sized α-Al2O3 and microsilica as starting materials. This work focused on investigating the relationship between the bond change in the castable matrix and the strength of the castable with 5 mass% microsilica or without microsilica after heat treatment at 110, 800 and 1 000 ℃, respectively. Chemical bond changes between the microsilica and hy- drates of calcium aluminate cement after drying at 110 ℃ or firing at 800 ℃ were investigated by XPS and FTIR. The results show that Si-O-Al bonds form be- tween the microsilica and hydrates of calcium aluminate cement after drying at 110 ℃ or firing at 800 ℃. Therefore, the increased strength of castable specimens is attributed to the formation of Si-O-Al bonds from 110 ℃ to 800 ℃.展开更多
Chemical bond properties of YBa 2Cu 3O 7 were studied by using the average ba nd-gap model. The calculated results show that the covalency of Cu(1)-O bond i s 0.406, and one of Cu(2)-O is 0.276. Mssbauer isomer shi...Chemical bond properties of YBa 2Cu 3O 7 were studied by using the average ba nd-gap model. The calculated results show that the covalency of Cu(1)-O bond i s 0.406, and one of Cu(2)-O is 0.276. Mssbauer isomer shifts of 57Fe in Y-123 were calculated by the chemical surrounding factor h v defined b y covalency and electronic polarizability. The charge-state and site of Fe were determined. The relation between the coupling constant of electron-phonon inte raction and covalency is employed to explain that the Cu(2)-O plane is more im portant than the Cu(1)-O chain on the superconductivity in the Y-123 compound s.展开更多
The electronic structures,chemical bonding,elastic and optical properties of the novel hP24 phase WB3 were investigated by using density-functional theory(DFT) within generalized gradient approximation(GGA).The calcul...The electronic structures,chemical bonding,elastic and optical properties of the novel hP24 phase WB3 were investigated by using density-functional theory(DFT) within generalized gradient approximation(GGA).The calculated energy band structures show that the hP24 phase WB3 is metallic material.The density of state(DOS) and the partial density of state(PDOS) calculations show that the DOS near the Fermi level is mainly from the W 5d and B 2p states.Population analysis suggests that the chemical bonding in hP24-WB3 has predominantly covalent characteristics with mixed covalent-ionic characteristics.Basic physical properties,such as lattice constant,bulk modulus,shear modulus and elastic constants Cij were calculated.The elastic modulus E and Poisson ratio υ were also predicted.The results show that hP24-WB3 phase is mechanically stable and behaves in a brittle manner.Detailed analysis of all optical functions reveals that WB3 is a better dielectric material,and reflectivity spectra show that WB3 can be promised as good coating material in the energy regions of 8.5-11.4 eV and 14.5-15.5 eV.展开更多
In the petrochemical industry process, the relative volatility between the components to be separated is close to one or the azeotrope that systems are difficult to separate. Liquid-liquid extraction is a common and e...In the petrochemical industry process, the relative volatility between the components to be separated is close to one or the azeotrope that systems are difficult to separate. Liquid-liquid extraction is a common and effective separation method, and selecting an extraction agent is the key to extraction technology research. In this paper, a design method of extractants based on elements and chemical bonds was proposed. A knowledge-based molecular design method was adopted to pre-select elements and chemical bond groups. The molecules were automatically synthesized according to specific combination rules to avoid the problem of “combination explosion” of molecules. The target properties of the extractant were set, and the extractant meeting the requirements was selected by predicting the correlation physical properties of the generated molecules. Based on the separation performance of the extractant in liquid-liquid extraction and the relative importance of each index, the fuzzy comprehensive evaluation membership function was established, the analytic hierarchy process determined the mass ratio of each index, and the consistency test results were passed. The results of case study based on quantum chemical analysis demonstrated that effective determination of extractants for the analysis of benzene-cyclohexane systems. The results unanimously prove that the method has important theoretical significance and application value.展开更多
Te-Se glass and adding As,Ge elements to it are studied with Selt-Consistent-Field Discrete Variatioal X(a)(SEF-DV-X(a)),one of the molecule orbital calculating methods in quantum chemistry.The chemical bonding is use...Te-Se glass and adding As,Ge elements to it are studied with Selt-Consistent-Field Discrete Variatioal X(a)(SEF-DV-X(a)),one of the molecule orbital calculating methods in quantum chemistry.The chemical bonding is used to discuss the relations between structures and properties with the varations of compositions of the glasses.The calculated results show that the strength of covalent and ionic bonds are both in the order of Ge-Se>As-Se>Te-Se,which is consistent with the experimental result of the glass-transition temperature(T-g)of the corresponding grasses.The Te-I bond in which I atom is one-coordinate is stronger than that in which I atom is two-coordinate,As-I and As-As bonds are both stronger than the two types of Te-I bonds.The waek Te-I bonds have been replaced by the stronger As-I and As-As bonds,which is just the reason why As addition in TeX glasses can obviously improve the thermal and chemical properties.展开更多
By using the average band-gap model, the chemical bond properties of(La_(1-x)M_x)_2CuO_4(M=Ba, Sr) were calculated . The calculated covalencies for Cu-O and La-O bondin the compounds are 0.3 and 0.03 respectively. Mos...By using the average band-gap model, the chemical bond properties of(La_(1-x)M_x)_2CuO_4(M=Ba, Sr) were calculated . The calculated covalencies for Cu-O and La-O bondin the compounds are 0.3 and 0.03 respectively. Mossbauer isomer shifts of ^(57)Fe doped inLa_2CuO_4 and ^(119)Sn doped in La_2CuO_4 were calculated by using the chemical surrounding factordefined by covalency and electronic polarizability. Four valence state tin and three valence ironsites were identified in ^(57)Fe and ^(119)Sn展开更多
The electronic structure, magnetic states, chemical bonding, and thermodynamic properties of β-US2 are investigated by using first-principles calculation through the density functional theory（DFT） ＋U approach. The...The electronic structure, magnetic states, chemical bonding, and thermodynamic properties of β-US2 are investigated by using first-principles calculation through the density functional theory（DFT） ＋U approach. The obtained band structure exhibits a direct band gap semiconductor at Γ point with a band gap of 0.9 e V for β-US2, which is in good agreement with the recent experimental data. The charge-density differences, the Bader charge analysis, and the Born effective charges suggest that the U–S bonds of the β-US2 have a mixture of covalent and ionic characters, but the ionic character is stronger than covalent character. The Raman-active, infrared-active, and silent modes at the Γ point are further assigned and discussed. The obtained optical-mode frequencies indicate that the three apparent LO–TO（longitudinal optical–transverse optical） splittings occur in B1 u, B2 u, and B3 umodes, respectively. Furthermore, the Helmholtz free energy ？F, the specific heat ？E, vibrational entropy S, and constant volume CVare studied over a range from 0 K-100 K. We expect that our work can provide some valuable information for further experimental investigation of the dielectric properties and the infrared reflectivity spectrum of uranium chalcogenide.展开更多
The nonrelativistic DV-X_α-SCC method was used to study the electronic structure and chemi- cal bonding of tetranuclear neodymium complex Nd_4O(OR)_4(NR′_2)_6,with emphasis on the bonding charac- ter of the central ...The nonrelativistic DV-X_α-SCC method was used to study the electronic structure and chemi- cal bonding of tetranuclear neodymium complex Nd_4O(OR)_4(NR′_2)_6,with emphasis on the bonding charac- ter of the central μ_4-O atom and the four Nd atoms.The results of calculation show that the μ_4-O atom uses its sp^3 valence orbitals to contribute four O-Nd bonding MOs with character of multicenter bond apparent- ly.The Mulliken population analysis shows that the overlap population between Nd atoms is almost equal to zero,therefore there is no direct metal-metal bond between Nd atoms.The coordination number of Nd in the complex is discussed briefly.展开更多
A model system,which is based on iron(Fe)doped gallium oxide(Ga_(2)O_(3))(Ga_(1.9)Fe_(0.1)O_(3)),has been considered to elucidate the combined effect of transition-metal ion doping and processing temperature on the ch...A model system,which is based on iron(Fe)doped gallium oxide(Ga_(2)O_(3))(Ga_(1.9)Fe_(0.1)O_(3)),has been considered to elucidate the combined effect of transition-metal ion doping and processing temperature on the chemistry,local structure and chemical bonding,and electrical transport properties of a wide band gap oxide(Ga_(2)O_(3)).The Ga_(1.9)Fe_(0.1)O_(3) compounds were synthesized using standard high-temperature solid state reaction method.The effect of processing conditions in terms of different calcination and sintering environments on the structural and electrical properties of Ga_(1.9)Fe_(0.1)O_(3) compounds is studied in detail.Structural characterization by Raman spectroscopy revealed that Ga_(1.9)Fe_(0.1)O_(3) compounds exhibit monoclinic crystal symmetry,which is quite similar to the intrinsic parental crystal structure,though Fedoping induces lattice strain.Sintering temperature(T_(sint))which was varied in the range of 900-1200℃,has significant impact on the structure,chemical bonding,and electrical properties of Ga_(1.9)Fe_(0.1)O_(3) compounds.Raman spectroscopic measurements indicate the proper densification of the Ga_(1.9)Fe_(0.1)O_(3) compounds achieved through complete Fe diffusion into the parent Ga_(2)O_(3) lattice which is evident at the highest sintering temperature.The X-ray photoelectron spectroscopy validates the chemical states of the constituent elements in Ga_(1.9)Fe_(0.1)O_(3) compounds.The electrical properties of Ga_(1.9)Fe_(0.1)O_(3) fully controlled by T_(sint),which governed the grain size and microstructural evolution.The temperature and frequency dependent electrical measurements demonstrated the salient features of the Fe doped Ga_(2)O_(3) compounds.The activation energy determined from Arrhenius equation is 0.5 e V.The results demonstrate that control over structure,morphology,chemistry and electrical properties of the Ga_(1.9)Fe_(0.1)O_(3) compounds can be achieved by optimizing T_(sint).展开更多
文摘Dielectric materials are essential in modern electronics,serving as the backbone of numerous components across a wide array of electronic devices[1,2].As technology advances,the demand for materials with high permittivity,low dielectric loss,and thermal stability continues to rise.Traditional strategies to enhance permittivity often involve mechanisms such as phase transitions in ferroelectrics or interfacial polarization in boundary layer capacitor(IBLC)systems.However,each comes with trade-offs.
基金supported by the NSFC-Zhejiang Joint Fund for Integration of Industrialization and Diversification(No.U1809214)the Natural Science Foundation of Zhejiang Province(Nos.LTGN23E080001 and LY20E080014)+1 种基金the Science and Technology Project of Zhoushan(No.2022C41011)the National Natural Science Foundation of China(No.22201251).
文摘Devising robust S-scheme photocatalysts is of central importance for achieving high-efficient micropollu-tant decontamination.However,the conscious optimization of S-scheme system with high performance remains a prime challenge.Herein,carbon quantum dots(CDs)and Mn_(0.5)Cd_(0.5)S(MCS)are mounted on BiOBr(BOB)microspheres,establishing an advanced S-scheme heterojunction with interfacial Bi-S bond.The interfacial Bi-S bonds function as superb channels at atomic-scale to abate the energy barrier for S-scheme charge transportation.Meanwhile,CDs serve as electron collectors to preserve highly reductive electrons from MCS,further augmenting the spatial separation of photo-carriers.Therefore,the optimized CDs/MCS/BOB(MBC)heterojunction manifests significantly strengthened tetracycline hydrochloride(TC)destruction activity and its reaction rate constant is approximately 3.1,2.2,2.1,and 1.5 folds that than that of MCS,BOB,BOB/CDs and MCS/BOB.In addition,MBC exhibits high stability and significant resistance to environmental interferences.The toxicology evaluation confirms the effective abatement of toxicity of TC after treatment.This achievement demonstrates the benefits of CDs-optimized S-scheme photosystems with chemical bonds for photocatalytic water decontamination.
基金Project (60571043) supported by the National Natural Science Foundation of ChinaProject (11JJ2002) supported by the Natural Science Foundation of Hunan Province, China
文摘The electronic structures, chemical bonding and elastic properties of the tetragonal phase BiOCuS were investigated by using density-functional theory （DFT） within generalized gradient approximation （GGA）. The calculated energy band structures show that the tetragonal phase BiOCuS is an indirect semiconductor with the calculated band gap of about 0.503 eV. The density of states （DOS） and the partial density of states （PDOS） calculations show that the DOS near the Fermi level is mainly from the Cu-3d state. Population analysis suggests that the chemical bonding in BiOCuS has predominantly ionic character with mixed covalent-ionic character. Basic physical properties, such as lattice constant, bulk modulus, shear modulus, elastic constants, were calculated. The elastic modulus and Poisson ratio were also predicted. The results show that tetragonal phase BiOCuS is mechanically stable and behaves in a ductile manner.
基金Project(11271121)supported by the National Natural Science Foundation of ChinaProject(11JJ2002)supported by the Natural Science Foundation of Hunan Province,China+1 种基金Project(11K038)supported by Key Laboratory of High Performance Computing and Stochastic Information Processing of Hunan Province,ChinaProject(2013GK3130)supported by the Scientific and Technological Plan Project of Hunan Province,China
文摘The electronic structures, chemical bonding and elastic properties of the Co2P-type structure phase ultra-incompressible Re2P （orthorhombic phase） were investigated by density-functional theory （DFT） within generalized gradient approximation （GGA）. The calculated energy band structures show that the orthorhombic structure phase Re2P is metallic material. The density of state （DOS） and the partial density of state （PDOS） calculations show that the DOS near the Fermi level is mainly from the Re-5d state. Population analysis suggests that the chemical bonding in Re2P has predominantly covalent character with mixed covalent-ionic character. Basic physical properties, such as lattice constant, bulk modulus, shear modulus, and elastic constants Cij, were calculated. The elastic modulus and Poisson ratio were also predicted. The results show that the Co2P-type structure phase Re2P is mechanically stable and behaves in a brittle manner.
基金Project(50474051)supported by the National Natural Science Foundation of China
文摘The structural parameters, chemical bonding and elastic properties of the tetragonal phase quaternary arsenide oxides YZnAsO and LaZnAsO were investigated by using density-functional theory （DFT） within generalized gradient approximation （GGA）. The GGA calculated structural parameters are in agreement with the experimental results. Population analysis suggests that the chemical bonding in YZnAsO and LaZnAsO can be classified as a mixture of ionic and covalent characteristic. Single-crystal elastic constants were calculated and the polycrystalline elastic modules were estimated according to Voigt, Reuss and Hill＇s approximations （VRH）. The result shows that both YZnAsO and LaZnAsO are relatively soft materials exhibiting ductile behavior. The calculated polycrystalline elastic anisotropy result shows that LaZnAsO is more anisotropy in compressibility and YZnAsO is more anisotropy in shear.
文摘The relation among electronic structure, chemical bond and thermoelectric property of Ca3 Co2 O6 and Ni-doped was studied by density function theory and discrete variation method（DFT-DVM）. The results indicate that the highest valence band（ HVB ）attd the lowest conduction band（ LCB ） are mainly attribuled to Co3d, Ni3d and O2p atomic orbitals. The property of a semiconductor is shown from the gap between HVB and LCB. The gap of Ni-doped one is less than that of Ca3 Co2 O6. The non-metal bond or ceramic characteristic of Ni-doped one is weaker than that of Ca3 Co2 O6, but the metal characteristics of Ni-doped one are stronger than those of Ca3 Co2 O6. The thermoelectric property should be improved by adding Ni element into the system of Ca3 Co2 O6 .
基金Financial support from the National Natural Science Foundation of China (22178190)the Major Science and Technology Innovation Project of Shandong Province (2018CXGC1102) is gratefully acknowledged。
文摘Molecular property depends on the property, the number of the elements, and the interaction between elements(such as chemical bonds). Based on the above-mentioned idea, two methods to estimate the isobaric heat capacity of liquids organic compounds were developed. Ten elements groups and 32 chemical bond groups were defined by considering the structure of organic compounds. The group contribution values and correlation parameters were regressed by the ridge regression method with the experiment data of 1137 compounds. The heat capacity can be calculated by summating the contributions of the elements and chemical bond groups. The two methods were compared with existing group contribution methods, such as Chickos, Zabransky-Ruzicka, and Zdenka Kolska. The results show that those new estimation methods' overall average relative deviations were 5.81% and 5.71%, which were lower than the other three methods. Those methods were more straightforward in compound splitting.Those new methods can be used to estimate the liquid heat capacity of silicon-containing compounds,which the other three methods cannot estimate. The new methods are more accessible, broader, and more accurate. Therefore, this research has important scientific significance and vast application prospects.
基金supported by the National Natural Science Foundation of China(51125009,91434118,21401185,21521092)Hundred Talents Program of Chinese Academy of SciencesJilin Province Science and Technology Development Project(20170101092JC,20160520006JH)
文摘The chemical bonding nature of rare earth（RE） elements can be studied by a quantitative analysis of electron domain of an atom. The outer electrons of RE elements are within the valence shell 4f^（0-14）5d^（0-1）6s^2, which are involved in all chemical bonding features. We in this work found that the chemical bonding characteristics of 4f electrons are a kind of hybridizations, and classified them into three types of chemical bonding of 4f^（0-14）5d^（0-1）6s^2, furthermore, the coordination number ranging from 2 to 16 could thus be determined. We selected Y（NO_3）_3, La（NO_3）_3, Ce（NO_3）_3, YCl_3, LaCl_3, and CeCl_3 as examples to in-situ observe their IR spectra of chemical bonding behaviors of Y^（3＋）, La^（3＋） and Ce^（3＋） cations, which could show different chemical bonding modes of 4f and 5d electrons. In the present study, we obtained the direct criterion to confirm whether 4f electrons can participate in chemical bonding, that is, only when the coordination number of RE cations is larger than 9.
文摘Titanium diboride was calculated by the density function and discrete variational (DFT-DVM) method to study the relation between structure and properties.Titanium and its first-nearest boron atoms form a strong covalent bond,so TiB 2 has high melting point,hardness and chemical stability.Titanium atom releases two electrons to form Ti 2+ ions,and a boron atom gets one electron to come into B- ion.B- takes the sp2 hybrid and forms σ bonds to link other boron atoms in the same layer.The other one 2p z orbital of every B- ion in the same layer interacts each other to form the π molecular orbital,so TiB 2 has fine electrical property.The calculated density of state is close to the result of XPS experiment of TiB 2.Mainly Ti3d and B2p atomic orbitals contribute the total DOS near the Fermi level.
基金supported by the National Natural Science Foundation of China(Nos.31771026 and 81771984)Project of State Key Laboratory of Ophthalmology,Optometry and Visual Science,Wenzhou Medical University(J02-20190203)the Wenzhou Key Program of Scientific and Technological Innovation(No.ZY2019017)。
文摘Eye trauma, decreased immunity, and contact lens wear often cause serious bacterial infections and irreversible corneal damage. To realize the responsive release of antibiotics such as gentamicin sulfate(GS), a novel antibacterial contact lens was constructed through self-assembly of antibiotics loaded ADAGS/PEI(polyethyleneimine) multilayer films on the surface. Both in vitro and in vivo antibacterial tests demonstrated high efficient and fast antibacterial property based on the smart responsive to bacterial infections and reversible drug loading and release.
文摘The relation among electronic structure, chemical bond and property of Ti3SiC2 and Al-doped was studied by density function and discrete variation （ DFT- DVM） method. When Al element is added into Ti3 SiC2 , there is a less difference of ionic bond, which does not play a leading role to influent the properties. After adding Al, the covalent bond of Al and the near Ti becomes somewhat weaker, but the covalent bond of Al and the Si in the same layer is obviously stronger than that of Si and Si before adding. Therefore, in preparation of Ti3 SiC2 , adding a proper quantity of Al can promote the formation of Ti3 SiC2 . The density of stnte shows that there is a mixed conductor character in both of Ti3 SiC2 and adding Al element. Ti3 SiC2 is with more tendencies to form a semiconductor. The total density of state near Fermi lever after adding Al is larger than that before adding, so the electric conductivity may increase after adding Al.
文摘Calcium aluminate cement bonded corundum castable specimens were prepared using brown fused corundum （8 - 5, 5 - 3, 3 - 1 mm ） , white fused corundum （ ≤ 1, ≤0. 045 mm）, micro-sized α-Al2O3 and microsilica as starting materials. This work focused on investigating the relationship between the bond change in the castable matrix and the strength of the castable with 5 mass% microsilica or without microsilica after heat treatment at 110, 800 and 1 000 ℃, respectively. Chemical bond changes between the microsilica and hy- drates of calcium aluminate cement after drying at 110 ℃ or firing at 800 ℃ were investigated by XPS and FTIR. The results show that Si-O-Al bonds form be- tween the microsilica and hydrates of calcium aluminate cement after drying at 110 ℃ or firing at 800 ℃. Therefore, the increased strength of castable specimens is attributed to the formation of Si-O-Al bonds from 110 ℃ to 800 ℃.
文摘Chemical bond properties of YBa 2Cu 3O 7 were studied by using the average ba nd-gap model. The calculated results show that the covalency of Cu(1)-O bond i s 0.406, and one of Cu(2)-O is 0.276. Mssbauer isomer shifts of 57Fe in Y-123 were calculated by the chemical surrounding factor h v defined b y covalency and electronic polarizability. The charge-state and site of Fe were determined. The relation between the coupling constant of electron-phonon inte raction and covalency is employed to explain that the Cu(2)-O plane is more im portant than the Cu(1)-O chain on the superconductivity in the Y-123 compound s.
基金Project(11271121)supported by the National Natural Science Foundation of ChinaProject(11JJ2002)supported by the Natural Science Foundation of Hunan Province,China+1 种基金Project(11K038)supported by Key Laboratory of Computational and Stochastic Mathematics of Ministry of Education of ChinaProject(2013GK3130)supported by the Scientific and Technological Plan of Hunan Province,China
文摘The electronic structures,chemical bonding,elastic and optical properties of the novel hP24 phase WB3 were investigated by using density-functional theory(DFT) within generalized gradient approximation(GGA).The calculated energy band structures show that the hP24 phase WB3 is metallic material.The density of state(DOS) and the partial density of state(PDOS) calculations show that the DOS near the Fermi level is mainly from the W 5d and B 2p states.Population analysis suggests that the chemical bonding in hP24-WB3 has predominantly covalent characteristics with mixed covalent-ionic characteristics.Basic physical properties,such as lattice constant,bulk modulus,shear modulus and elastic constants Cij were calculated.The elastic modulus E and Poisson ratio υ were also predicted.The results show that hP24-WB3 phase is mechanically stable and behaves in a brittle manner.Detailed analysis of all optical functions reveals that WB3 is a better dielectric material,and reflectivity spectra show that WB3 can be promised as good coating material in the energy regions of 8.5-11.4 eV and 14.5-15.5 eV.
基金supported by the National Natural Science Foundation of China(22178190).
文摘In the petrochemical industry process, the relative volatility between the components to be separated is close to one or the azeotrope that systems are difficult to separate. Liquid-liquid extraction is a common and effective separation method, and selecting an extraction agent is the key to extraction technology research. In this paper, a design method of extractants based on elements and chemical bonds was proposed. A knowledge-based molecular design method was adopted to pre-select elements and chemical bond groups. The molecules were automatically synthesized according to specific combination rules to avoid the problem of “combination explosion” of molecules. The target properties of the extractant were set, and the extractant meeting the requirements was selected by predicting the correlation physical properties of the generated molecules. Based on the separation performance of the extractant in liquid-liquid extraction and the relative importance of each index, the fuzzy comprehensive evaluation membership function was established, the analytic hierarchy process determined the mass ratio of each index, and the consistency test results were passed. The results of case study based on quantum chemical analysis demonstrated that effective determination of extractants for the analysis of benzene-cyclohexane systems. The results unanimously prove that the method has important theoretical significance and application value.
文摘Te-Se glass and adding As,Ge elements to it are studied with Selt-Consistent-Field Discrete Variatioal X(a)(SEF-DV-X(a)),one of the molecule orbital calculating methods in quantum chemistry.The chemical bonding is used to discuss the relations between structures and properties with the varations of compositions of the glasses.The calculated results show that the strength of covalent and ionic bonds are both in the order of Ge-Se>As-Se>Te-Se,which is consistent with the experimental result of the glass-transition temperature(T-g)of the corresponding grasses.The Te-I bond in which I atom is one-coordinate is stronger than that in which I atom is two-coordinate,As-I and As-As bonds are both stronger than the two types of Te-I bonds.The waek Te-I bonds have been replaced by the stronger As-I and As-As bonds,which is just the reason why As addition in TeX glasses can obviously improve the thermal and chemical properties.
文摘By using the average band-gap model, the chemical bond properties of(La_(1-x)M_x)_2CuO_4(M=Ba, Sr) were calculated . The calculated covalencies for Cu-O and La-O bondin the compounds are 0.3 and 0.03 respectively. Mossbauer isomer shifts of ^(57)Fe doped inLa_2CuO_4 and ^(119)Sn doped in La_2CuO_4 were calculated by using the chemical surrounding factordefined by covalency and electronic polarizability. Four valence state tin and three valence ironsites were identified in ^(57)Fe and ^(119)Sn
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21371160 and 21401173)
文摘The electronic structure, magnetic states, chemical bonding, and thermodynamic properties of β-US2 are investigated by using first-principles calculation through the density functional theory（DFT） ＋U approach. The obtained band structure exhibits a direct band gap semiconductor at Γ point with a band gap of 0.9 e V for β-US2, which is in good agreement with the recent experimental data. The charge-density differences, the Bader charge analysis, and the Born effective charges suggest that the U–S bonds of the β-US2 have a mixture of covalent and ionic characters, but the ionic character is stronger than covalent character. The Raman-active, infrared-active, and silent modes at the Γ point are further assigned and discussed. The obtained optical-mode frequencies indicate that the three apparent LO–TO（longitudinal optical–transverse optical） splittings occur in B1 u, B2 u, and B3 umodes, respectively. Furthermore, the Helmholtz free energy ？F, the specific heat ？E, vibrational entropy S, and constant volume CVare studied over a range from 0 K-100 K. We expect that our work can provide some valuable information for further experimental investigation of the dielectric properties and the infrared reflectivity spectrum of uranium chalcogenide.
基金The project supported by the National Natural Science Foundation of China
文摘The nonrelativistic DV-X_α-SCC method was used to study the electronic structure and chemi- cal bonding of tetranuclear neodymium complex Nd_4O(OR)_4(NR′_2)_6,with emphasis on the bonding charac- ter of the central μ_4-O atom and the four Nd atoms.The results of calculation show that the μ_4-O atom uses its sp^3 valence orbitals to contribute four O-Nd bonding MOs with character of multicenter bond apparent- ly.The Mulliken population analysis shows that the overlap population between Nd atoms is almost equal to zero,therefore there is no direct metal-metal bond between Nd atoms.The coordination number of Nd in the complex is discussed briefly.
基金support from the National Science Foundation(NSF)with grant#DMR-1827745。
文摘A model system,which is based on iron(Fe)doped gallium oxide(Ga_(2)O_(3))(Ga_(1.9)Fe_(0.1)O_(3)),has been considered to elucidate the combined effect of transition-metal ion doping and processing temperature on the chemistry,local structure and chemical bonding,and electrical transport properties of a wide band gap oxide(Ga_(2)O_(3)).The Ga_(1.9)Fe_(0.1)O_(3) compounds were synthesized using standard high-temperature solid state reaction method.The effect of processing conditions in terms of different calcination and sintering environments on the structural and electrical properties of Ga_(1.9)Fe_(0.1)O_(3) compounds is studied in detail.Structural characterization by Raman spectroscopy revealed that Ga_(1.9)Fe_(0.1)O_(3) compounds exhibit monoclinic crystal symmetry,which is quite similar to the intrinsic parental crystal structure,though Fedoping induces lattice strain.Sintering temperature(T_(sint))which was varied in the range of 900-1200℃,has significant impact on the structure,chemical bonding,and electrical properties of Ga_(1.9)Fe_(0.1)O_(3) compounds.Raman spectroscopic measurements indicate the proper densification of the Ga_(1.9)Fe_(0.1)O_(3) compounds achieved through complete Fe diffusion into the parent Ga_(2)O_(3) lattice which is evident at the highest sintering temperature.The X-ray photoelectron spectroscopy validates the chemical states of the constituent elements in Ga_(1.9)Fe_(0.1)O_(3) compounds.The electrical properties of Ga_(1.9)Fe_(0.1)O_(3) fully controlled by T_(sint),which governed the grain size and microstructural evolution.The temperature and frequency dependent electrical measurements demonstrated the salient features of the Fe doped Ga_(2)O_(3) compounds.The activation energy determined from Arrhenius equation is 0.5 e V.The results demonstrate that control over structure,morphology,chemistry and electrical properties of the Ga_(1.9)Fe_(0.1)O_(3) compounds can be achieved by optimizing T_(sint).
