Three-phase NaCl-H_2O fluid inclusions featuring halite dissolution temperature（Tm）higher than vapor bubble disappearance temperature（T_h） are commonly observed in porphyry copper/molybdenum deposits,skarn-type de...Three-phase NaCl-H_2O fluid inclusions featuring halite dissolution temperature（Tm）higher than vapor bubble disappearance temperature（T_h） are commonly observed in porphyry copper/molybdenum deposits,skarn-type deposits and other magmatic- hydrothermal ore deposits.Based on ｜ΔV_1｜（the absolute value of volume variation of NaCl-H_2O solution in a heating or cooling process of inclusions）= ｜ΔV_s｜（the absolute value of volume variation of the halite crystal in a heating or cooling process of inclusions） and on the principle of conservation of the mass of NaCl and H_2O,we systematically calculated the densities of NaCl-H_2O solutions in the solid-liquid two-phase field for temperatures（T_h） from 0.1℃ to 800℃ and salinities from 26.3 wt%to 99.2wt%.Consequently for the first time we obtained the upper limit of the density of NaCI-H_2O solutions in the solid-liquid twophase field for T_b〈T_m inclusions with variant salinities.The results indicate that for inclusions of the T_h〈T_m type with the same T_h,the higher the T_m or salinity is,the higher the density of the NaClsaturated solution will be.If a group of fluid inclusions were homogeneously trapped,they must have the same T_h value and the same T_m or salinity value.This may be used to distinguish homogeneous,inhomogeneous,and multiple entrapments of fluid inclusions.展开更多
A supramolecular 1D ferromagnetic system was studied experimentally as well as theoretically.Hybrid density functional theory（DFT） calculations were based on the X-ray analysis.The results of DFT calculations and Mc...A supramolecular 1D ferromagnetic system was studied experimentally as well as theoretically.Hybrid density functional theory（DFT） calculations were based on the X-ray analysis.The results of DFT calculations and McConnell mechanism have contributed to the understanding of the factors governing the exchange coupling of magnetism in the crystal packing.Both the experimental evidence and theoretical calculation indicate that spin density in 2-iodo nitronyl nitroxide（INN） radicals confirms 1D ferromagnetic chain with inter-chain antiferromagnetic interaction.展开更多
We investigated the structural evolution and elecfronic properties of ConC3-/0 and ConC4-/0 （n=1-4） clusters by using mass-selected photoelectron spectroscopy and density functional theory calculations. The adiabati...We investigated the structural evolution and elecfronic properties of ConC3-/0 and ConC4-/0 （n=1-4） clusters by using mass-selected photoelectron spectroscopy and density functional theory calculations. The adiabatic and vertical detachment energies of CO1-4C3- and COl-4C4- were obtained from their photoelectron spectra. By comparing the theoretical results with the experimental data, the global minimum structures were determined. The results indicate that the carbon atoms of ConC3-/0 and ConC4-/0 （n=1-4） are separated from each other gradually with increasing number of cobalt atoms but a C2 unit still remains at n=4. It is interesting that the Co2C3- and Co2C4- anions have planar structures whereas the neutral Co2C3 and Co2C4 have linear structures with the Co atoms at two ends. The Co3C3- anion has a planar structure with a Co2C2 four-membered ring and a Co3C four-membered ring sharing a Co-Co bond, while the neutral Co3C3 is a three-dimensional structure with a C2 unit and a C atom connecting to two faces of the Co3 triangle.展开更多
Palladium oxide(PdOx)and cobalt oxide(Co3O4)are efficient catalysts for methane(CH4)combustion,and Pd‐doped Co3O4catalysts have been found to exhibit better catalytic activities,which suggest synergism between the tw...Palladium oxide(PdOx)and cobalt oxide(Co3O4)are efficient catalysts for methane(CH4)combustion,and Pd‐doped Co3O4catalysts have been found to exhibit better catalytic activities,which suggest synergism between the two components.We carried out first‐principles calculations at the PBE+U level to investigate the Pd‐doping effect on CH4reactivity over the Co3O4catalyst.Because of the structural complexity of the Pd‐doped Co3O4catalyst,we built Pd‐doped catalyst models using Co3O4(001)slabs with two different terminations and examined CH4reactivity over the possible Pd?O active sites.A low energy barrier of0.68eV was predicted for CH4dissociation over the more reactive Pd‐doped Co3O4(001)surface,which was much lower than the0.98and0.89eV that was predicted previously over the more reactive pure Co3O4(001)and(011)surfaces,respectively.Using a simple model,we predicted CH4reaction rates over the pure Co3O4(001)and(011)surfaces,and Co3O4(001)surfaces with different amounts of Pd dopant.Our theoretical results agree well with the available experimental data,which suggests a strong synergy between the Pd dopant and the Co3O4catalyst,and leads to a significant increase in CH4reaction rate.展开更多
The development of highly active DFT catalysts for an electrocatalytic N_(2)reduction reaction(NRR)under mild conditions is a difficult challenge.In this study,a series of atom‐pair catalysts(APCs)for an NRR were fab...The development of highly active DFT catalysts for an electrocatalytic N_(2)reduction reaction(NRR)under mild conditions is a difficult challenge.In this study,a series of atom‐pair catalysts(APCs)for an NRR were fabricated using transition‐metal(TM)atoms(TM=Sc−Zn)doped into g‐CN monolayers.The electrochemical mechanism of APCs for an NRR has been reported by well‐defined density functional theory calculations.The calculated limiting potentials were−0.47 and−0.78 V for the Fe_(2)@CN and Co_(2)@CN catalysts,respectively.Owing to its high suppression of hydrogen evolution reactions,Co_(2)@CN is a superior electrocatalytic material for a N_(2)fixation.Stable Fe_(2)@CN may be a strongly attractive material for an NRR with a relatively low overpotential after an improvement in the selectivity.The two‐way charge transfer affirmed the donation‐acceptance procedure between N_(2)and Fe_(2)@CN or Co_(2)@CN,which play a crucial role in the activation of inert N≡N bonds.This study provides an in‐depth investigation into atom‐pair catalysts and will open up new avenues for highly efficient g‐CN‐based nanostructures for an NRR.展开更多
Equilibrium structures and infrared spectra of four typical molecular models of coal have been studied by density functional calculations. Combining theoretical calculations on the coal models with experimental FT-IR ...Equilibrium structures and infrared spectra of four typical molecular models of coal have been studied by density functional calculations. Combining theoretical calculations on the coal models with experimental FT-IR spectra of selected low rank perhydrous coals, a plausible molecular representation for this kind of coals was proposed, and its predicted IR spectra reasonably match the experimental observation. Calculations indicate that the cleavage of the C-C bridge bond for the coal structures considered here occurs at about 540 ℃ and the C-O ether bridge bond may break under temperature ranging from 500 to 600 ℃for the aryl-CH2-O-CH2-aryl ether bond or from 200 to 300 ℃ for the aryl-CH2-O-aryl ether bond, showing remarkable effect of the local structural environment. The coal model containing the carboxyl group may release CO2 at about 300 ℃ through the decarboxylation with a barrier of 69 kcal/mol.展开更多
Bond dissociation energies for the removal of nitrogen dioxide group in some nitroalkane energetic materials have been calculated by using the three hybrid density functional theory （DFT） methods B3LYP, B3PW91 and B...Bond dissociation energies for the removal of nitrogen dioxide group in some nitroalkane energetic materials have been calculated by using the three hybrid density functional theory （DFT） methods B3LYP, B3PW91 and B3P86 with 6-31g^＊＊ and 6-311g^＊＊ basis sets. The computed BDEs have been compared with the available experimental results. It is found that the B3P86 method with 6-31g^＊＊ and 6-311g^＊＊ basis sets can obtain satisfactory bond dissociation energies （BDEs）, which are in extraordinary agreement with the experimental data. Considering the smaller mean absolute deviation and maximum difference, the reliable B3P86/6-311g^＊＊ method was recommended to compute the BDEs for the removal of nitrogen dioxide group in the nitroalkane energetic materials. Using the method, the BDEs of 8 other nitroalkane energetic materials have been calculated and the maximum difference from experimental value is 1.76 kcal.mo1^-1 （for the BDE of tC4Hg-NOz）, which further proves the reliability of B3P86/6-311g^＊＊ method. In addition, it is noted that the BDEs of C-NO2 bond change slightly for main chain nitroalkane compounds with the maximum difference of only 3.43 kcal mo1^-1.展开更多
The wurtzite MnO has been obtained lately and is expected to have large potentiai in varies applications. Since elastic properties are the bases of various applications, we calculate these properties of wurtzite MnO b...The wurtzite MnO has been obtained lately and is expected to have large potentiai in varies applications. Since elastic properties are the bases of various applications, we calculate these properties of wurtzite MnO based on the density-functionai theory and compare it with other two phases of MnO （rocksalt and zinc-blende MnO）. The Young＇s modulus of wurtzite and zinc-blende MnO are 65.6 GPa and 73.4 GPa, respectively, which are much lower than those of rocksaJt MnO （177.6 GPa）. More importantly, both the Poisson ratio and the bulk modulus to shear modulus ratio indicate that wurtzite MnO should have much better ductile properties than rocksalt MnO. The calculated piezoelectric constants of wurtzite MnO are comparable to those of ZnO, This suggests wurtzite MnO is a good piezoelectric material. Furthermore, the slowness surfaces of acoustic waves of them are given from Christoffel equation.展开更多
Pd-Rh nanoparticles are known to easily undergo surface restructuring in reactive environment. This study quantifies, with the help of density functional(DFT) calculations and a novel topological approach, atomic orde...Pd-Rh nanoparticles are known to easily undergo surface restructuring in reactive environment. This study quantifies, with the help of density functional(DFT) calculations and a novel topological approach, atomic ordering and surface segregation effects in Pd-Rh particles with compositions 1:3, 1:1 and 3:1 containing up to 201 atoms(ca. 1.7 nm). The obtained data are used to reliably optimise energetically preferred atomic orderings in inaccessible by DFT Pd-Rh particles containing thousands of atoms and exhibiting sizes exceeding 5 nm, which are typical for catalytic metal particles. It is outlined, how segregation effects on the surface arrangement of Pd-Rh nanoalloy catalysts induced by adsorbates can be evaluated in a simple way within the present modelling setup.展开更多
The local structure of an alternative Pb（Zn1/3Nb2/3）O3-based perovskite ceramic is investigated. The 0.07BaTiO33-0.93Pb（Zn1/3Nb2/3）O3 ceramic is synthesized using a combination of Zn3Nb2O8 B-site precursor and BaT...The local structure of an alternative Pb（Zn1/3Nb2/3）O3-based perovskite ceramic is investigated. The 0.07BaTiO33-0.93Pb（Zn1/3Nb2/3）O3 ceramic is synthesized using a combination of Zn3Nb2O8 B-site precursor and BaTiO33 perovskite phase stabilizer. Then, x-ray absorption spectroscopy and density functional theory are employed to calculate the local structure configuration and formation energy of the prepared samples. Ba2＋ is found to replace Pb2＋ in AA-site with Zn2＋ occupying BB-site in Pb（Zn1/3Nb2/3）O3, while in the neighboring structure, Ti4＋4＋ replaces Nb5＋5＋ in BB-site with Pb2＋2＋ occupying AA-site. With the substitution of BaTiO33 in Pb（Zn1/3Nb2/3）O3, the bond length between Zn2＋ and Pb2＋ is longer than that of the typical perovskite phase of Pb（Zn1/3Nb2/3）O3. This indicates the key role of BaTiO33 in decreasing the steric hindrance of Pb2＋ lone pair, and the mutual interactions between Pb2＋ lone pair and Zn2＋ and the formation energy is seen to decrease. This finding of the formation energy and local structure configuration relationship can further extend a fundamental understanding of the role of BaTiO33 in stabilizing the perovskite phase in PbZn13Nb23O3-based materials, which in turn will lead to an improved preparation technique for desired electrical properties.展开更多
The equilibrium geometry and electronic structure of pyrite has been studied using self consistent density functional theory within the local density approximation (LDA). The optimum bulk geometry is in good agreement...The equilibrium geometry and electronic structure of pyrite has been studied using self consistent density functional theory within the local density approximation (LDA). The optimum bulk geometry is in good agreement with crystallographic data. The calculated band structure and density of states in the region around the Fermi energy show that valence band maximum (VBM) is at X (100), and the conduction band minimum (CBM) is at G (000). The indirect and direct band gaps are 0.6?eV and 0.74?eV, respectively. The calculated contour map of difference of charge density shows excess charge in nonbonding d electron states on the Fe sites. The density increases between sulfur nuclei and between iron and sulfur nuclei qualitatively reveal that S-S bond and Fe-S bond are covalent binding.展开更多
This paper studies supersonic jet-cooled 1-fluoronaphthalene （1FN） clusters by ultraviolet （UV） laser ionization at 281 nm in a time-of-flight mass spectrometer. The （1FN）＋ （n=1-3） series cluster ions are obs...This paper studies supersonic jet-cooled 1-fluoronaphthalene （1FN） clusters by ultraviolet （UV） laser ionization at 281 nm in a time-of-flight mass spectrometer. The （1FN）＋ （n=1-3） series cluster ions are observed where the signal intensity decreases with increasing cluster size. The effects of sample inlet pressures and ionization laser fluxes to mass spectral distribution are measured. Using density functional theory calculations, it obtains a planar geometric structure of 1FN dimer which is combined through two hydrogen bonds. The mass spectra indicate that the intensity of 1FN trimer is much weaker than that of 1FN dimer and this feature is attributed to the fact that the dimer may form the first ＂shell＂ in geometric structure while the larger clusters are generated based on this fundamental unit.展开更多
Arsenic can diffuse into high-κ dielectrics during OaAs-based metal oxide semiconductor transistor process, which causes the degradation of gate dielectrics. To explore the origins of the degradation, we employ nonlo...Arsenic can diffuse into high-κ dielectrics during OaAs-based metal oxide semiconductor transistor process, which causes the degradation of gate dielectrics. To explore the origins of the degradation, we employ nonlocal B3LYP hybrid functional to study arsenic related defects in ZrO2. Via band alignments between the OaAs and ZrO2, we are able to determine the defect formation energy in the GaAs relative to the ZrO2 band gap and assess how they will affect the device performance. Arsenic at the interstitial site serves as a source of positive fixed charge while at the oxygen or zirconium substitutional site changes its charge state within the band gap of GaAs. Moreover, it is found that arsenic related defects produce conduction band offset reduction and gap states, which will increase the gate leakage current.展开更多
In this paper, we perform the density functional theory （DFT） -based calculations by the first-principles pseudopo- tential method to investigate the physical properties of the newly discovered superconductor LaRu2A...In this paper, we perform the density functional theory （DFT） -based calculations by the first-principles pseudopo- tential method to investigate the physical properties of the newly discovered superconductor LaRu2As2 for the first time. The optimized structural parameters are in good agreement with the experimental results. The calculated independent elas- tic constants ensure the mechanical stability of the compound. The calculated Cauchy pressure, Pugh＇s ratio as well as Poisson＇s ratio indicate that LaRu2As2 should behave as a ductile material. Due to low Debye temperature, LaRu2As2 may be used as a thermal barrier coating （TBC） material. The new compound should exhibit metallic nature as its valence bands overlap considerably with the conduction bands. LaRu2As2 is expected to be a soft material and easily machinable because of its low hardness value of 6.8 GPa. The multi-band nature is observed in the calculated Fermi surface. A highly anisotropic combination of ionic, covalent and metallic interactions is expected to be in accordance with charge density calculation.展开更多
A first-principles density functional approach is used to study the electronic and the elastic properties of Nb15X （X = Ti, Zr, Hf, V, Ta, Cr, Mo, and W） alloys. The elastic constants cn and c12, the shear modulus C...A first-principles density functional approach is used to study the electronic and the elastic properties of Nb15X （X = Ti, Zr, Hf, V, Ta, Cr, Mo, and W） alloys. The elastic constants cn and c12, the shear modulus CI, and the elastic modulus E（lOO） are found to exhibit similar tendencies, each as a function of valence electron number per atom （EPA）, while c44 seems unclear. Both cu and c12 of Nb15X alloys increase monotonically with the increase of EPA. The C/ and E000） also show similar tendencies. The elastic constants （except c44） increase slightly when alloying with neighbours of a higher d-transition series. Our results are supported by the bonding density distribution. When solute atoms change from Ti（Zr, Hf） to V（Ta） then to Cr（Mo, W）, the bonding electron density between the central solute atom and its first neighbouring Nb atoms is increased and becomes more anisotropic, which indicates the strong interaction and thus enhances the elastic properties of Nb-Cr（Mo, W） alloys. Under uniaxial {100） tensile loading, alloyed elements with less （more） valence electrons decrease （increase） the ideal tensile strength.展开更多
The role of additional ternary alloying elements on the performance of stationary TiFe-based hydrogen storage alloys was investigated based on first-principles density functional theory calculations.As a basic step fo...The role of additional ternary alloying elements on the performance of stationary TiFe-based hydrogen storage alloys was investigated based on first-principles density functional theory calculations.As a basic step for examinations,the site preference of each alloying element in the stoichiometric and nonstoichiometric B2TiFe compounds was clarified considering possible antisite defects.Based on the revealed site preference,the effect of various possible ternary elements on the hydrogen storage was examined by focusing on the formation enthalpies of TiFeH and TiFeH_(2) hydrides,which were closely related to the change in the location of plateaus in the pressure-composition-temperature curve.Several physical properties such as the volume expansion due to hydride formation were also examined to provide additional criteria for selecting optimum alloying conditions in future alloying design processes.Candidate alloying elements that maximize the grain boundary embrittlement due to the solute segregation were proposed for the enhanced initial activation of TiFe-based hydrogen storage alloys.展开更多
Decomposition of the polycation Al_(13)O_(4)(OH)_(2)4(H_(2)O)_(12)^(7+)(Al_(13))promoted by ligand is a vital subject to advance our understanding of natural and artificial occurrence and evolution of aluminum ions,es...Decomposition of the polycation Al_(13)O_(4)(OH)_(2)4(H_(2)O)_(12)^(7+)(Al_(13))promoted by ligand is a vital subject to advance our understanding of natural and artificial occurrence and evolution of aluminum ions,especially in the case of acidic condition that dissolved Al^(3+)species can be released from the Al-bearing substances.However,the microscopic pathway of synchronous proton-promoted and ligand-promoted decomposition process for Al_(13)is still in the status of ambiguity.Herein,we applied differential mass spectrometry method and DFT calculation to study the initial detailed process of Al_(13)decomposition under the presence of proton and salicylic acid(H_(2)Sal).Mass results showed that the mononuclear Al^(3+)-H_(2)Sal complexes dominated the resulting Al species,whereas the monodentate complex Al_(13)HSal6+was not observed in the spectra.The difference of decomposition levels between the ligand/Al ratio 0.2 and 0.5 cases revealed that proton and ligand performed synergistic effect in initial Al_(13)decomposition process,and the proton transfer determined the ring closure efficiency.The ring closure reaction is the prerequisite for the collapse of Al_(13)structure and detachment of the mononuclear complex.DFT calculations reveal that hydrogen bond plays an important role in inducing the formation of chelated complex accompanying proton transfer.Attachment of protons at the bridging OH^(-)can elongate and weaken the critical bond between targeted Al^(3+)andμ4-O_(2)-resulting from delocalization of electron pairs in the oxygen atom.These results demonstrate the detailed mechanism of Al_(13)composition promoted by ligand and proton,and provide significant understanding for further application and control of Al_(13).展开更多
Rational design of high-performance electrocatalysts for hydrogen evolution reaction(HER)is vital for future renewable energy systems.The incorporation of foreign metal ions into catalysts can be an effective approach...Rational design of high-performance electrocatalysts for hydrogen evolution reaction(HER)is vital for future renewable energy systems.The incorporation of foreign metal ions into catalysts can be an effective approach to optimize its performance.However,there is a lack of systematic theoretical studies to reveal the quantitative relationships at the electronic level.Here,we develop a multi-level screening methodology to search for highly stable and active dopants for CoP catalysts.The density functional theory(DFT)calculations and symbolic regression(SR)were performed to investigate the relationship between the adsorption free energy(ΔG_(H^(*)))and 10 electronic parameters.The mathematic formulas derived from SR indicate that the difference of work function(ΔΦ)between doped metal and the acceptor plays the most important role in regulatingΔG_(H^(*)),followed by the d-band center(d-BC)of doped system.The descriptor of HER can be expressed asΔG_(H^(*))=1.59×√|0.188ΔΦ+d BC+0.120|1/2-0.166 with a high determination coefficient(R^(2)=0.807).Consistent with the theoretical prediction,experimental results show that the Al-CoP delivers superior electrocatalytic HER activity with a low overpotential of75 m V to drive a current density of 10 mA cm^(-2),while the overpotentials for undoped CoP,Mo-CoP,and V-CoP are 206,134,and 83 m V,respectively.The current work proves that theΔΦis the most significant regulatory parameter ofΔG_(H^(*))for ion-doped electrocatalysts.This finding can drive the discovery of high-performance ion-doped electrocatalysts,which is crucial for electrocatalytic water splitting.展开更多
The rational fabrication of heterostructures is one of efficient strategies for improving photocatalytic performance of semiconductor photocatalysts.Very recently,Domen and co-workers found that Ta_(3)N_(5) single cry...The rational fabrication of heterostructures is one of efficient strategies for improving photocatalytic performance of semiconductor photocatalysts.Very recently,Domen and co-workers found that Ta_(3)N_(5) single crystals grown on the surface of KTaO_(3) can accomplish photocatalytic overall water splitting for the first time.In order to comprehend the underlying mechanism of this photocatalytic system,we have performed a systematic study based on density functional theory first-principles calculations.Ta_(3)N_(5)(010)/KTaO_(3)(110)slab models have been built according to experimental observations by considering two common terminations of KTaO_(3)(110)surface,named as Ta_(3)N_(5)/O_(2) and Ta_(3)N_(5)/KTaO.The formations of interfacial bonds are thermodynamically stable,showing a covalent interaction between two components of a heterostructure.Ta_(3)N_(5)/O_(2) has a higher mobility of photogenerated charge carriers and lower recombination rate of charge carriers than Ta_(3)N_(5)/KTaO.The light absorption of heterostructures displays the feature of KTaO_(3) in the short wavelength region and the characteristic of Ta_(3)N_(5) in the long wavelength region.The calculated band offsets show that Ta_(3)N_(5)/O_(2) and Ta_(3)N_(5)/KTaO have distinct Type-II band alignments,with Ta_(3)N_(5) as the accumulator of photoinduced electrons in the former and the collector of photogenerated holes in the latter,respectively.The difference in charge density and electrostatic potential between two components acts as a driving force to promote the transfer of electrons and holes to different domains of the interface,which is beneficial to extend the lifetime of photoinduced carriers.Our results demonstrate that the function of Ta_(3)N_(5) in Ta_(3)N_(5)/KTaO_(3) photocatalytic system is determined by the termination property of KTaO_(3)(110)surface,which provides a likely reason of the observed photocatalytic activity of overall water splitting achieved by Ta_(3)N_(5) synthesized by using KTaO_(3) as a precursor for the nitridation reaction.展开更多
The thermodynamic stability and lithiated/delithiated potentials of LiFexMn1-xPO4 were studied with density functional theorical calculations. The results show that the formation free energy of the LiFexMn1-xPO4 solid...The thermodynamic stability and lithiated/delithiated potentials of LiFexMn1-xPO4 were studied with density functional theorical calculations. The results show that the formation free energy of the LiFexMn1-xPO4 solid solution is slightly higher than that of the phase-separated mixture of LiFePO4 and LiMnPO4, and the two forms may co-exist in the actual LiFexMn1-xPO4 materials. The calculation manifests that the lithiated/delithiated potentials of LiFexMn1-xPO4 solid solutions vary via the Mn/Fe ratio and the spatial arrangements of the transition metal ions, and the result is used to explain the shape of capacity-voltage curves. Experimentally, we have synthesized the LiFexMn1-xPO4 materials by solid-phase reaction method. The existence of the LiFexMn1-xPO4 solid solution is thought to be responsible for the appearance of additional capacity-voltage plateau observed in the experiment.展开更多
基金supported by China National Natural Science Foundation(No.4997032)the Basic Business Fee Special Foundation for Chinese central nonprofit research institutes(K0710)
文摘Three-phase NaCl-H_2O fluid inclusions featuring halite dissolution temperature（Tm）higher than vapor bubble disappearance temperature（T_h） are commonly observed in porphyry copper/molybdenum deposits,skarn-type deposits and other magmatic- hydrothermal ore deposits.Based on ｜ΔV_1｜（the absolute value of volume variation of NaCl-H_2O solution in a heating or cooling process of inclusions）= ｜ΔV_s｜（the absolute value of volume variation of the halite crystal in a heating or cooling process of inclusions） and on the principle of conservation of the mass of NaCl and H_2O,we systematically calculated the densities of NaCl-H_2O solutions in the solid-liquid two-phase field for temperatures（T_h） from 0.1℃ to 800℃ and salinities from 26.3 wt%to 99.2wt%.Consequently for the first time we obtained the upper limit of the density of NaCI-H_2O solutions in the solid-liquid twophase field for T_b〈T_m inclusions with variant salinities.The results indicate that for inclusions of the T_h〈T_m type with the same T_h,the higher the T_m or salinity is,the higher the density of the NaClsaturated solution will be.If a group of fluid inclusions were homogeneously trapped,they must have the same T_h value and the same T_m or salinity value.This may be used to distinguish homogeneous,inhomogeneous,and multiple entrapments of fluid inclusions.
基金Supported by the National Natural Science Foundation of China(No.21061009)
文摘A supramolecular 1D ferromagnetic system was studied experimentally as well as theoretically.Hybrid density functional theory（DFT） calculations were based on the X-ray analysis.The results of DFT calculations and McConnell mechanism have contributed to the understanding of the factors governing the exchange coupling of magnetism in the crystal packing.Both the experimental evidence and theoretical calculation indicate that spin density in 2-iodo nitronyl nitroxide（INN） radicals confirms 1D ferromagnetic chain with inter-chain antiferromagnetic interaction.
文摘We investigated the structural evolution and elecfronic properties of ConC3-/0 and ConC4-/0 （n=1-4） clusters by using mass-selected photoelectron spectroscopy and density functional theory calculations. The adiabatic and vertical detachment energies of CO1-4C3- and COl-4C4- were obtained from their photoelectron spectra. By comparing the theoretical results with the experimental data, the global minimum structures were determined. The results indicate that the carbon atoms of ConC3-/0 and ConC4-/0 （n=1-4） are separated from each other gradually with increasing number of cobalt atoms but a C2 unit still remains at n=4. It is interesting that the Co2C3- and Co2C4- anions have planar structures whereas the neutral Co2C3 and Co2C4 have linear structures with the Co atoms at two ends. The Co3C3- anion has a planar structure with a Co2C2 four-membered ring and a Co3C four-membered ring sharing a Co-Co bond, while the neutral Co3C3 is a three-dimensional structure with a C2 unit and a C atom connecting to two faces of the Co3 triangle.
基金supported by the National Natural Science Foundation of China(21473233,21403277)the Energy Technologies Institute LLP,UK~~
文摘Palladium oxide(PdOx)and cobalt oxide(Co3O4)are efficient catalysts for methane(CH4)combustion,and Pd‐doped Co3O4catalysts have been found to exhibit better catalytic activities,which suggest synergism between the two components.We carried out first‐principles calculations at the PBE+U level to investigate the Pd‐doping effect on CH4reactivity over the Co3O4catalyst.Because of the structural complexity of the Pd‐doped Co3O4catalyst,we built Pd‐doped catalyst models using Co3O4(001)slabs with two different terminations and examined CH4reactivity over the possible Pd?O active sites.A low energy barrier of0.68eV was predicted for CH4dissociation over the more reactive Pd‐doped Co3O4(001)surface,which was much lower than the0.98and0.89eV that was predicted previously over the more reactive pure Co3O4(001)and(011)surfaces,respectively.Using a simple model,we predicted CH4reaction rates over the pure Co3O4(001)and(011)surfaces,and Co3O4(001)surfaces with different amounts of Pd dopant.Our theoretical results agree well with the available experimental data,which suggests a strong synergy between the Pd dopant and the Co3O4catalyst,and leads to a significant increase in CH4reaction rate.
文摘The development of highly active DFT catalysts for an electrocatalytic N_(2)reduction reaction(NRR)under mild conditions is a difficult challenge.In this study,a series of atom‐pair catalysts(APCs)for an NRR were fabricated using transition‐metal(TM)atoms(TM=Sc−Zn)doped into g‐CN monolayers.The electrochemical mechanism of APCs for an NRR has been reported by well‐defined density functional theory calculations.The calculated limiting potentials were−0.47 and−0.78 V for the Fe_(2)@CN and Co_(2)@CN catalysts,respectively.Owing to its high suppression of hydrogen evolution reactions,Co_(2)@CN is a superior electrocatalytic material for a N_(2)fixation.Stable Fe_(2)@CN may be a strongly attractive material for an NRR with a relatively low overpotential after an improvement in the selectivity.The two‐way charge transfer affirmed the donation‐acceptance procedure between N_(2)and Fe_(2)@CN or Co_(2)@CN,which play a crucial role in the activation of inert N≡N bonds.This study provides an in‐depth investigation into atom‐pair catalysts and will open up new avenues for highly efficient g‐CN‐based nanostructures for an NRR.
基金supported by the Ministry of Science and Technology (2012CB214900 and 2011CB808504)the National Science Foundation of China (21133007)
文摘Equilibrium structures and infrared spectra of four typical molecular models of coal have been studied by density functional calculations. Combining theoretical calculations on the coal models with experimental FT-IR spectra of selected low rank perhydrous coals, a plausible molecular representation for this kind of coals was proposed, and its predicted IR spectra reasonably match the experimental observation. Calculations indicate that the cleavage of the C-C bridge bond for the coal structures considered here occurs at about 540 ℃ and the C-O ether bridge bond may break under temperature ranging from 500 to 600 ℃for the aryl-CH2-O-CH2-aryl ether bond or from 200 to 300 ℃ for the aryl-CH2-O-aryl ether bond, showing remarkable effect of the local structural environment. The coal model containing the carboxyl group may release CO2 at about 300 ℃ through the decarboxylation with a barrier of 69 kcal/mol.
基金The project was supported by the National Natural Science Foundation of China (No. 10574096 and 10676025)
文摘Bond dissociation energies for the removal of nitrogen dioxide group in some nitroalkane energetic materials have been calculated by using the three hybrid density functional theory （DFT） methods B3LYP, B3PW91 and B3P86 with 6-31g^＊＊ and 6-311g^＊＊ basis sets. The computed BDEs have been compared with the available experimental results. It is found that the B3P86 method with 6-31g^＊＊ and 6-311g^＊＊ basis sets can obtain satisfactory bond dissociation energies （BDEs）, which are in extraordinary agreement with the experimental data. Considering the smaller mean absolute deviation and maximum difference, the reliable B3P86/6-311g^＊＊ method was recommended to compute the BDEs for the removal of nitrogen dioxide group in the nitroalkane energetic materials. Using the method, the BDEs of 8 other nitroalkane energetic materials have been calculated and the maximum difference from experimental value is 1.76 kcal.mo1^-1 （for the BDE of tC4Hg-NOz）, which further proves the reliability of B3P86/6-311g^＊＊ method. In addition, it is noted that the BDEs of C-NO2 bond change slightly for main chain nitroalkane compounds with the maximum difference of only 3.43 kcal mo1^-1.
文摘The wurtzite MnO has been obtained lately and is expected to have large potentiai in varies applications. Since elastic properties are the bases of various applications, we calculate these properties of wurtzite MnO based on the density-functionai theory and compare it with other two phases of MnO （rocksalt and zinc-blende MnO）. The Young＇s modulus of wurtzite and zinc-blende MnO are 65.6 GPa and 73.4 GPa, respectively, which are much lower than those of rocksaJt MnO （177.6 GPa）. More importantly, both the Poisson ratio and the bulk modulus to shear modulus ratio indicate that wurtzite MnO should have much better ductile properties than rocksalt MnO. The calculated piezoelectric constants of wurtzite MnO are comparable to those of ZnO, This suggests wurtzite MnO is a good piezoelectric material. Furthermore, the slowness surfaces of acoustic waves of them are given from Christoffel equation.
基金financed by the Generalitat de Catalunya via a pre-doctoral grant 2018FI-B-00384the Operational program“Science and Education for Smart Growth”,project BG05M2OP001-2.009-0028 for funding his research stay in the University of Barcelona+2 种基金financial support by the Bulgarian Ministry of Education and Science under the National Research Programme“Low-carbon Energy for the Transportsupport by the Spanish grants PGC2018-093863-B-C22,CTQ2015-64618-RMDM-2017-0767 as well as by the grant 2017SGR13 of the Generalitat de Catalunya
文摘Pd-Rh nanoparticles are known to easily undergo surface restructuring in reactive environment. This study quantifies, with the help of density functional(DFT) calculations and a novel topological approach, atomic ordering and surface segregation effects in Pd-Rh particles with compositions 1:3, 1:1 and 3:1 containing up to 201 atoms(ca. 1.7 nm). The obtained data are used to reliably optimise energetically preferred atomic orderings in inaccessible by DFT Pd-Rh particles containing thousands of atoms and exhibiting sizes exceeding 5 nm, which are typical for catalytic metal particles. It is outlined, how segregation effects on the surface arrangement of Pd-Rh nanoalloy catalysts induced by adsorbates can be evaluated in a simple way within the present modelling setup.
基金Supported by the Thailand Research Fund under Grant No TRG5880097
文摘The local structure of an alternative Pb（Zn1/3Nb2/3）O3-based perovskite ceramic is investigated. The 0.07BaTiO33-0.93Pb（Zn1/3Nb2/3）O3 ceramic is synthesized using a combination of Zn3Nb2O8 B-site precursor and BaTiO33 perovskite phase stabilizer. Then, x-ray absorption spectroscopy and density functional theory are employed to calculate the local structure configuration and formation energy of the prepared samples. Ba2＋ is found to replace Pb2＋ in AA-site with Zn2＋ occupying BB-site in Pb（Zn1/3Nb2/3）O3, while in the neighboring structure, Ti4＋4＋ replaces Nb5＋5＋ in BB-site with Pb2＋2＋ occupying AA-site. With the substitution of BaTiO33 in Pb（Zn1/3Nb2/3）O3, the bond length between Zn2＋ and Pb2＋ is longer than that of the typical perovskite phase of Pb（Zn1/3Nb2/3）O3. This indicates the key role of BaTiO33 in decreasing the steric hindrance of Pb2＋ lone pair, and the mutual interactions between Pb2＋ lone pair and Zn2＋ and the formation energy is seen to decrease. This finding of the formation energy and local structure configuration relationship can further extend a fundamental understanding of the role of BaTiO33 in stabilizing the perovskite phase in PbZn13Nb23O3-based materials, which in turn will lead to an improved preparation technique for desired electrical properties.
文摘The equilibrium geometry and electronic structure of pyrite has been studied using self consistent density functional theory within the local density approximation (LDA). The optimum bulk geometry is in good agreement with crystallographic data. The calculated band structure and density of states in the region around the Fermi energy show that valence band maximum (VBM) is at X (100), and the conduction band minimum (CBM) is at G (000). The indirect and direct band gaps are 0.6?eV and 0.74?eV, respectively. The calculated contour map of difference of charge density shows excess charge in nonbonding d electron states on the Fe sites. The density increases between sulfur nuclei and between iron and sulfur nuclei qualitatively reveal that S-S bond and Fe-S bond are covalent binding.
文摘This paper studies supersonic jet-cooled 1-fluoronaphthalene （1FN） clusters by ultraviolet （UV） laser ionization at 281 nm in a time-of-flight mass spectrometer. The （1FN）＋ （n=1-3） series cluster ions are observed where the signal intensity decreases with increasing cluster size. The effects of sample inlet pressures and ionization laser fluxes to mass spectral distribution are measured. Using density functional theory calculations, it obtains a planar geometric structure of 1FN dimer which is combined through two hydrogen bonds. The mass spectra indicate that the intensity of 1FN trimer is much weaker than that of 1FN dimer and this feature is attributed to the fact that the dimer may form the first ＂shell＂ in geometric structure while the larger clusters are generated based on this fundamental unit.
基金Supported by the Key Project of Education Department of China under Grant No 211035the Science Foundation from Education Department of Liaoning Province under Grant No L2014445
文摘Arsenic can diffuse into high-κ dielectrics during OaAs-based metal oxide semiconductor transistor process, which causes the degradation of gate dielectrics. To explore the origins of the degradation, we employ nonlocal B3LYP hybrid functional to study arsenic related defects in ZrO2. Via band alignments between the OaAs and ZrO2, we are able to determine the defect formation energy in the GaAs relative to the ZrO2 band gap and assess how they will affect the device performance. Arsenic at the interstitial site serves as a source of positive fixed charge while at the oxygen or zirconium substitutional site changes its charge state within the band gap of GaAs. Moreover, it is found that arsenic related defects produce conduction band offset reduction and gap states, which will increase the gate leakage current.
文摘In this paper, we perform the density functional theory （DFT） -based calculations by the first-principles pseudopo- tential method to investigate the physical properties of the newly discovered superconductor LaRu2As2 for the first time. The optimized structural parameters are in good agreement with the experimental results. The calculated independent elas- tic constants ensure the mechanical stability of the compound. The calculated Cauchy pressure, Pugh＇s ratio as well as Poisson＇s ratio indicate that LaRu2As2 should behave as a ductile material. Due to low Debye temperature, LaRu2As2 may be used as a thermal barrier coating （TBC） material. The new compound should exhibit metallic nature as its valence bands overlap considerably with the conduction bands. LaRu2As2 is expected to be a soft material and easily machinable because of its low hardness value of 6.8 GPa. The multi-band nature is observed in the calculated Fermi surface. A highly anisotropic combination of ionic, covalent and metallic interactions is expected to be in accordance with charge density calculation.
基金Project supported by the National Natural Science Foundation of China(Grant No.50771004)
文摘A first-principles density functional approach is used to study the electronic and the elastic properties of Nb15X （X = Ti, Zr, Hf, V, Ta, Cr, Mo, and W） alloys. The elastic constants cn and c12, the shear modulus CI, and the elastic modulus E（lOO） are found to exhibit similar tendencies, each as a function of valence electron number per atom （EPA）, while c44 seems unclear. Both cu and c12 of Nb15X alloys increase monotonically with the increase of EPA. The C/ and E000） also show similar tendencies. The elastic constants （except c44） increase slightly when alloying with neighbours of a higher d-transition series. Our results are supported by the bonding density distribution. When solute atoms change from Ti（Zr, Hf） to V（Ta） then to Cr（Mo, W）, the bonding electron density between the central solute atom and its first neighbouring Nb atoms is increased and becomes more anisotropic, which indicates the strong interaction and thus enhances the elastic properties of Nb-Cr（Mo, W） alloys. Under uniaxial {100） tensile loading, alloyed elements with less （more） valence electrons decrease （increase） the ideal tensile strength.
基金supported by the National Research Foundation of Korea(NRF)funded by Ministry of Science and ICT(Nos.NRF-2019M3E6A1103984 and NRF-2019M3D1A1079214)。
文摘The role of additional ternary alloying elements on the performance of stationary TiFe-based hydrogen storage alloys was investigated based on first-principles density functional theory calculations.As a basic step for examinations,the site preference of each alloying element in the stoichiometric and nonstoichiometric B2TiFe compounds was clarified considering possible antisite defects.Based on the revealed site preference,the effect of various possible ternary elements on the hydrogen storage was examined by focusing on the formation enthalpies of TiFeH and TiFeH_(2) hydrides,which were closely related to the change in the location of plateaus in the pressure-composition-temperature curve.Several physical properties such as the volume expansion due to hydride formation were also examined to provide additional criteria for selecting optimum alloying conditions in future alloying design processes.Candidate alloying elements that maximize the grain boundary embrittlement due to the solute segregation were proposed for the enhanced initial activation of TiFe-based hydrogen storage alloys.
基金financially supported by the National Natural Science Foundation of China(Nos.52030003 and 51778604)。
文摘Decomposition of the polycation Al_(13)O_(4)(OH)_(2)4(H_(2)O)_(12)^(7+)(Al_(13))promoted by ligand is a vital subject to advance our understanding of natural and artificial occurrence and evolution of aluminum ions,especially in the case of acidic condition that dissolved Al^(3+)species can be released from the Al-bearing substances.However,the microscopic pathway of synchronous proton-promoted and ligand-promoted decomposition process for Al_(13)is still in the status of ambiguity.Herein,we applied differential mass spectrometry method and DFT calculation to study the initial detailed process of Al_(13)decomposition under the presence of proton and salicylic acid(H_(2)Sal).Mass results showed that the mononuclear Al^(3+)-H_(2)Sal complexes dominated the resulting Al species,whereas the monodentate complex Al_(13)HSal6+was not observed in the spectra.The difference of decomposition levels between the ligand/Al ratio 0.2 and 0.5 cases revealed that proton and ligand performed synergistic effect in initial Al_(13)decomposition process,and the proton transfer determined the ring closure efficiency.The ring closure reaction is the prerequisite for the collapse of Al_(13)structure and detachment of the mononuclear complex.DFT calculations reveal that hydrogen bond plays an important role in inducing the formation of chelated complex accompanying proton transfer.Attachment of protons at the bridging OH^(-)can elongate and weaken the critical bond between targeted Al^(3+)andμ4-O_(2)-resulting from delocalization of electron pairs in the oxygen atom.These results demonstrate the detailed mechanism of Al_(13)composition promoted by ligand and proton,and provide significant understanding for further application and control of Al_(13).
基金Financial support from the National Natural Science Foundation of China(21676216)the Special project of Shaanxi Provincial Education Department(20JC034)+1 种基金GHfund B(202202022563)Hefei Advanced Computing Center。
文摘Rational design of high-performance electrocatalysts for hydrogen evolution reaction(HER)is vital for future renewable energy systems.The incorporation of foreign metal ions into catalysts can be an effective approach to optimize its performance.However,there is a lack of systematic theoretical studies to reveal the quantitative relationships at the electronic level.Here,we develop a multi-level screening methodology to search for highly stable and active dopants for CoP catalysts.The density functional theory(DFT)calculations and symbolic regression(SR)were performed to investigate the relationship between the adsorption free energy(ΔG_(H^(*)))and 10 electronic parameters.The mathematic formulas derived from SR indicate that the difference of work function(ΔΦ)between doped metal and the acceptor plays the most important role in regulatingΔG_(H^(*)),followed by the d-band center(d-BC)of doped system.The descriptor of HER can be expressed asΔG_(H^(*))=1.59×√|0.188ΔΦ+d BC+0.120|1/2-0.166 with a high determination coefficient(R^(2)=0.807).Consistent with the theoretical prediction,experimental results show that the Al-CoP delivers superior electrocatalytic HER activity with a low overpotential of75 m V to drive a current density of 10 mA cm^(-2),while the overpotentials for undoped CoP,Mo-CoP,and V-CoP are 206,134,and 83 m V,respectively.The current work proves that theΔΦis the most significant regulatory parameter ofΔG_(H^(*))for ion-doped electrocatalysts.This finding can drive the discovery of high-performance ion-doped electrocatalysts,which is crucial for electrocatalytic water splitting.
基金financially supported by the Natural Science Foundation of Liaoning Province(Grant No.2019-ZD-0304)the Educational Department of Liaoning Province(Grant No.LJ2019009)+1 种基金Liaoning BaiQianWan Talents Program,Doctoral Start-up Foundation of Liaoning Province(Grant No.20170520231)the open fund of the State Key Laboratory of Molecular Reaction Dynamics in Dalian Institute of Chemical Physics(Grant No.SKLMRDK202001),Chinese Academy of Sciences。
文摘The rational fabrication of heterostructures is one of efficient strategies for improving photocatalytic performance of semiconductor photocatalysts.Very recently,Domen and co-workers found that Ta_(3)N_(5) single crystals grown on the surface of KTaO_(3) can accomplish photocatalytic overall water splitting for the first time.In order to comprehend the underlying mechanism of this photocatalytic system,we have performed a systematic study based on density functional theory first-principles calculations.Ta_(3)N_(5)(010)/KTaO_(3)(110)slab models have been built according to experimental observations by considering two common terminations of KTaO_(3)(110)surface,named as Ta_(3)N_(5)/O_(2) and Ta_(3)N_(5)/KTaO.The formations of interfacial bonds are thermodynamically stable,showing a covalent interaction between two components of a heterostructure.Ta_(3)N_(5)/O_(2) has a higher mobility of photogenerated charge carriers and lower recombination rate of charge carriers than Ta_(3)N_(5)/KTaO.The light absorption of heterostructures displays the feature of KTaO_(3) in the short wavelength region and the characteristic of Ta_(3)N_(5) in the long wavelength region.The calculated band offsets show that Ta_(3)N_(5)/O_(2) and Ta_(3)N_(5)/KTaO have distinct Type-II band alignments,with Ta_(3)N_(5) as the accumulator of photoinduced electrons in the former and the collector of photogenerated holes in the latter,respectively.The difference in charge density and electrostatic potential between two components acts as a driving force to promote the transfer of electrons and holes to different domains of the interface,which is beneficial to extend the lifetime of photoinduced carriers.Our results demonstrate that the function of Ta_(3)N_(5) in Ta_(3)N_(5)/KTaO_(3) photocatalytic system is determined by the termination property of KTaO_(3)(110)surface,which provides a likely reason of the observed photocatalytic activity of overall water splitting achieved by Ta_(3)N_(5) synthesized by using KTaO_(3) as a precursor for the nitridation reaction.
基金supported by the Science and Technology Foundation of Jiangsu Province(BK20151237)the Special Nano-technology of Suzhou(ZXG2013004)+2 种基金USTC-NSRL Association Fundingthe Collaborative Innovation Centre of Suzhou Nano Science and Technologythe Supercomputation Center of USTC
文摘The thermodynamic stability and lithiated/delithiated potentials of LiFexMn1-xPO4 were studied with density functional theorical calculations. The results show that the formation free energy of the LiFexMn1-xPO4 solid solution is slightly higher than that of the phase-separated mixture of LiFePO4 and LiMnPO4, and the two forms may co-exist in the actual LiFexMn1-xPO4 materials. The calculation manifests that the lithiated/delithiated potentials of LiFexMn1-xPO4 solid solutions vary via the Mn/Fe ratio and the spatial arrangements of the transition metal ions, and the result is used to explain the shape of capacity-voltage curves. Experimentally, we have synthesized the LiFexMn1-xPO4 materials by solid-phase reaction method. The existence of the LiFexMn1-xPO4 solid solution is thought to be responsible for the appearance of additional capacity-voltage plateau observed in the experiment.
