The structural, electronic, and optical properties of Cu2Zn1−xBaxSn1−ySiyS4 compounds have been calculated using GGA-PBE function within the framework of Density Functional Theory (DFT). In the present work, lattice p...The structural, electronic, and optical properties of Cu2Zn1−xBaxSn1−ySiyS4 compounds have been calculated using GGA-PBE function within the framework of Density Functional Theory (DFT). In the present work, lattice parameters remained the same, that is tetragonal crystal structure for 0% and 100% doping concentration. The electronic band gap of Cu2Zn1−xBaxSn1−ySiyS4 compounds has been gradually increased for continuous increment of doping concentration where the highest electronic band gap is 1.117 eV for Cu2BaSiS4 structure. Moreover, the band gap changes from direct to indirect band gap with the increase of doping concentration in the parent compound. The absorption coefficient has been found to be high (> 104 cm−1) in UV-region for all the doping concentration which makes the studied compound as a potential candidate of absorber layer in the UV detector. The theoretical study of the effect of double doping in the CZTS compound is very interesting for improving the quality of it and it would be a reference for the theoretical and experimental researchers.展开更多
In this study,a microscopic method for calculating the nuclear level density(NLD)based on the covariant density functional theory(CDFT)is developed.The particle-hole state density is calculated by a combinatorial meth...In this study,a microscopic method for calculating the nuclear level density(NLD)based on the covariant density functional theory(CDFT)is developed.The particle-hole state density is calculated by a combinatorial method using single-particle level schemes obtained from the CDFT,and the level densities are then obtained by considering collective effects such as vibration and rotation.Our results are compared with those of other NLD models,including phenomenological,microstatisti-cal and nonrelativistic Hartree–Fock–Bogoliubov combinatorial models.This comparison suggests that the general trends among these models are essentially the same,except for some deviations among the different NLD models.In addition,the NLDs obtained using the CDFT combinatorial method with normalization are compared with experimental data,including the observed cumulative number of levels at low excitation energies and the measured NLDs.The CDFT combinatorial method yields results that are in reasonable agreement with the existing experimental data.展开更多
Developing novel oxygen reduction reaction(ORR)catalysts with high activity is urgent for proton exchange membrane fuel cells.Herein,we investigated a group of size-dependent Pt-based catalysts as promising ORR cataly...Developing novel oxygen reduction reaction(ORR)catalysts with high activity is urgent for proton exchange membrane fuel cells.Herein,we investigated a group of size-dependent Pt-based catalysts as promising ORR catalysts by density functional theory calculations,ranging from single-atom,nanocluster to bulk Pt catalysts.The results showed that the ORR overpotential of these Pt-based catalysts increased when its size enlarged to the nanoparticle scale or reduced to the single-atom scale,and the Pt_(38)cluster had the lowest ORR overpotential(0.46 V)compared with that of Pt_(111)(0.57 V)and single atom Pt(0.7 V).Moreover,we established a volcano curve relationship between the ORR overpotential and binding energy of O*(ΔE_(O*),confirming the intermediate species anchored on Pt38cluster with suitable binding energy located at top of volcano curve.The interaction between intermediate species and Pt-based catalysts were also investigated by the charge distribution and projected density of state and which further confirmed the results of volcano curve.展开更多
In 2014, 50 years following the introduction of density functional theory (DFT), a rigorous understanding of it was published [AIP Advances, 4, 127,104 (2014)]. This understanding includes two features that complete t...In 2014, 50 years following the introduction of density functional theory (DFT), a rigorous understanding of it was published [AIP Advances, 4, 127,104 (2014)]. This understanding includes two features that complete the theory in practice, inasmuch as they are necessary for its correct application in electronic structure calculations;this understanding elucidates what appears to have been the crucial misunderstanding for 50 years, namely, the confusion between a stationary solution, attainable with most basis sets, following self-consistent iterations, with the ground state solution. The latter is obtained by a calculation that employs the well-defined optimal basis set for the system. The aim of this work is to review the above understanding and to extend it to the relativistic generalization of density functional theory by Rajagopal and Callaway [Phys. Rev. B7, 1912 (1973)]. This extension straightforwardly follows similar steps taken in the non-relativistic case, with the four-component current density, in the former, replacing the electronic charge density, in the latter. This new understanding, which completes relativistic DFT in practice, is expected to be needed for the study of heavy atoms and of materials (from molecules to solids) containing them—as is the case for some high temperature superconductors.展开更多
The plane-wave pseudopotential function method, based on density-functional theory, has been used to calculate the adsorption, electronic band structures, orbitals and optical absorption spectrum of [Fe（CN）6]^4- on ...The plane-wave pseudopotential function method, based on density-functional theory, has been used to calculate the adsorption, electronic band structures, orbitals and optical absorption spectrum of [Fe（CN）6]^4- on TiOz anatase（101） surface. Our calculations reveal that the surface-modified anatase system has large adsorption energy and a much narrower band gap. [Fe（CN）6]^4- adsorption on the （101） surface could lead to a large red shift of the anatase optical absorption threshold, which extends into a visible region significantly. The calculated results are in agreement with the experiment and other theoretical studies reasonably. It is very important for the understanding and further development ofphotovoltaic materials that are active under visible light.展开更多
Optimized calculation of 35 dialkyl phenyl phosphate compounds （OPs） was carded out at the B3LYP/6-31G^＊ level in Gaussian 98 program. Based on the theoretical linear solvation energy relationship （TLSER） model, ...Optimized calculation of 35 dialkyl phenyl phosphate compounds （OPs） was carded out at the B3LYP/6-31G^＊ level in Gaussian 98 program. Based on the theoretical linear solvation energy relationship （TLSER） model, the obtained parameters were taken as theoretical descriptors to establish the novel QSPR model for predicting n-octanol/water partition coefficients （lgKow） of OPs. The new model achieved in this work contains three variables, i.e., molecular volume （Vm）, dipole moment of the molecules （μ） and enthalpy （H^0）. For this model, R^2 = 0.9167 and SD = 0.31 at large t values. In addition, the variation inflation factors （VIF） of variables are all close to 1.0, suggesting high accuracy of the predicting model. And the results of cross-validation test （q^2 = 0.8993） and method validation also showed the model of this study exhibited optimum stability and better predictive power than that from semi-empirical method. The model achieved can be used to predict IgKow of congeneric compounds.展开更多
The thermodynamic properties of 135 polybrominated dibenzothiophenes （PBDTs） in the gaseous state at 298.15 K and 1.013×10^5 Pa, are calculated using the density functional theory （the B3LYP/6-311G^＊＊） wit...The thermodynamic properties of 135 polybrominated dibenzothiophenes （PBDTs） in the gaseous state at 298.15 K and 1.013×10^5 Pa, are calculated using the density functional theory （the B3LYP/6-311G^＊＊） with Gaussian 03. Based on these data, the isodesmic reacflons are designed to calculate the standard enthalpy of formation （△fH^θ） and the standard Gibbs energy of formation （△fG^θ） of PBDTs. The relations of these thermodynamic parameters with the number and positionof bromine subsfituents （NPBS） are discussed, and it is found that there exist good correlations between othermody namic parameters （including heat capacity at constant volume, entropy, enthaipy, free energy, △fH^θ, △fG^θ） and NPBS. Thoe relative stability order of PBDT congeners is proposed theoretically based on the relative magnitude of their △fG^θ. In addition, the values of molar heat capacities at constant pressure （Cp,m） for PBDT c ongelaers are calculated.展开更多
This paper applies a density functional theory （DFT） and grand canonical Monte Carlo simulations （GCMC） to investigate the physisorptions of molecular hydrogen in single-walled BC3 nanotubes and carbon nanotubes. ...This paper applies a density functional theory （DFT） and grand canonical Monte Carlo simulations （GCMC） to investigate the physisorptions of molecular hydrogen in single-walled BC3 nanotubes and carbon nanotubes. The DFT calculations may provide useful information about the nature of hydrogen adsorption and physisorption energies in selected adsorption sites of these two nanotubes. Furthermore, the GCMC simulations can reproduce their storage capacity by calculating the weight percentage of the adsorbed molecular hydrogen under different conditions. The present results have shown that with both computational methods, the hydrogen storage capacity of BC3 nanotubes is superior to that of carbon nanotubes. The reasons causing different behaviour of hydrogen storage in these two nanotubes are explained by using their contour plots of electron density and charge-density difference.展开更多
The electronic and physical properties of PtmPdn （m＋n≤5） metal clusters and their interactions with dioxygen have been studied by using hybrid density functional B3LYP method. The total energies, atomization energ...The electronic and physical properties of PtmPdn （m＋n≤5） metal clusters and their interactions with dioxygen have been studied by using hybrid density functional B3LYP method. The total energies, atomization energies, vibration frequencies, and charge distributions were reported. The Pt-Pt bridge site modified by Pd atoms was found to be the most active site for the dissociation of dioxygen, which was mainly due to the change of electronic structures of the Pt atoms in bimetallic Pt-Pd clusters.展开更多
The structural and thermodynamic （PCTAs） in the ideal gas state at 298.15 K and 1.013 properties of 75 polychlorinated thianthrenes ×10^5 Pa have been calculated at the B3LYP/6- 31G＊ level using Gaussian 98 pr...The structural and thermodynamic （PCTAs） in the ideal gas state at 298.15 K and 1.013 properties of 75 polychlorinated thianthrenes ×10^5 Pa have been calculated at the B3LYP/6- 31G＊ level using Gaussian 98 program. Based on the output data of Gaussian, the isodesmic reactions were designed to calculate standard enthalpy of formation （△fH^θ） and standard free energy of formation （△fH^θ） of PCTAs congeners. The relations of these thermodynamic parameters with the number and position of C1 atom substitution （Npcs） were discussed, and it was found that there exists high correlation between thermodynamic parameters （total energy （TE）, zero-point vibrational energy （ZPE）, thermal correction to energy （Eth）, heat capacity at constant volume （Cv^θ）, entropy （S^θ）, enthalpy （H^θ）, free energy （G^θ）, standard enthalpies of formation （△fH^θ） and standard Gibbs energies of formation （△fG^θ）） and Npcs. On the basis of the relative magnitude of their △fG^θ, the order of relative stability of PCTA congeners was theoretically proposed. In addition, the correlations between structural parameters and Npcs were also discussed. The good correlations were found between molecular average polarizability （α）, energy of the highest occupied molecular orbital （EHOMO）, molecular volume （Vm） and Npcs, and all R^2 values are larger than 0.95. Moreover, it was supposed that the isomer groups with higher toxicity should be Tri-CTA and TCTA.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
Based on the density functional calculations, the structural and electronic properties of the WS2/graphene heterojunction under different strains are investigated. The calculated results show that unlike the free mono...Based on the density functional calculations, the structural and electronic properties of the WS2/graphene heterojunction under different strains are investigated. The calculated results show that unlike the free mono-layer WS2, the monolayer WS2 in the equilibrium WS2/graphene heterojunctionis characterized by indirect band gap due to the weak van der Waals interaction. The height of the schottky barrier for the WS2/graphene heterojunction is 0.13 eV, which is lower than the conventional metal/MoS2 contact. Moreover, the band properties and height of schottky barrier for WS2/graphene heterojunction can be tuned by strain. It is found that the height of the schottky barrier can be tuned to be near zero under an in-plane compressive strain, and the band gap of the WS2 in the heterojunction is turned into a direct band gap from the indirect band gap with the increasing schottky barrier height under an in-plane tensile strain. Our calculation results may provide a potential guidance for designing and fabricating the WS2-based field effect transistors.展开更多
Density functional theory was applied to study the structure of Beta zeolite. A model cluster containing 41Si atoms, 1 Al atom, 70 O atoms and 29 H atoms was constructed. The model structures were optimized using the ...Density functional theory was applied to study the structure of Beta zeolite. A model cluster containing 41Si atoms, 1 Al atom, 70 O atoms and 29 H atoms was constructed. The model structures were optimized using the Becke＇s three-parameter hybrid method with the Lee-Yang-Parr correlation functional （B3LYP） and the 6-31G basis set applying the Gaussian03 program package. The NMR parameters were calculated to validate the rationality of the model. It was found that in the optimization models, all O-H bond lengths were in range of 0.984-0.985A^°, among which the model with O-H bond length of 0.98478A^° was more stable than the others. The ^1H and ^27Al chemical shifts of the most stable model were 4.03434 and 55.74 ppm, which were pretty consistent with Larry＇ s experimental data of 4.1 and 54 ppm. The relationship between other structure parameters and total relative electric energy has also been found. All the results exhibit that the 42 T （the total number of Si and Al atoms is 42） model has common properties of the standard of zeolite Beta.展开更多
Optimized calculation of dibenzofuran （DF） and 135 polychlorinated dibenzofurans （PCDFs） was carried out at the B3LYP/6-31G＊ level in GAUSSIAN 98 program. Based on the theoretical linear solvation energy relation...Optimized calculation of dibenzofuran （DF） and 135 polychlorinated dibenzofurans （PCDFs） was carried out at the B3LYP/6-31G＊ level in GAUSSIAN 98 program. Based on the theoretical linear solvation energy relationship （TLSER） model, the obtained structural parameters were taken as theoretical descriptors to establish the novel quantitative structureproperty relationship （QSPR） model for predicting n-octanol/water partition coefficients （lgKow） of PCDFs. The new model of lgKow achieved in this work contains three variables： energy of the highest occupied molecular orbital （EHOMO）, the most negative atomic partial charge （q^-） and average molecular polarizability （a）, of which R^2= 0.9011 and SD = 0,17 with larger t values. In addition, the variation inflation factors （VIF） of variables in the present model are all less than 5.5, suggesting high accuracy of the lgKow model. And the results of cross-validation test （q^2 = 0.8688） and method validation also show this model exhibits optimum stability and better predictive power than semi-empirical method. At the same time, it is found that the aqueous solubility （-lgSw） has high relative correlation with constant volume molar heat capacity （Cv^0）, of which R^2 = 0.9777 and SD = 0.22. Moreover, lgKow and -lgSw values of all PCDF congeners were predicted respectively.展开更多
We perform the first-principles investigations of the structural,elastic,electronic,and optical properties of SrBO3(B=Cr,Fe)perovskites under pressure based on density functional theory(DFT).This is the first detailed...We perform the first-principles investigations of the structural,elastic,electronic,and optical properties of SrBO3(B=Cr,Fe)perovskites under pressure based on density functional theory(DFT).This is the first detailed pressure-dependent study of the physical properties for these compounds.The calculated structural parameters are consistent with the existing experimental results and slightly decrease with the application of pressure.The mechanical properties are discussed in detail and reveal that the SrCrO3 is harder than SrFeO3.Without pressure,these compounds behave like half-metals,confirmed by their band structure and density of states.Although the SrCrO3 retains its half-metallic nature under pressure,SrFeO3 becomes metallic for both up-spin and down-spin configuration.Both charge density and bond overlap population reveal the covalent nature of Cr–O bond and Fe–O bond in the studied compounds.The optical properties of SrBO3,also discussed for the first time,reveal some interesting results.展开更多
Electronic properties, such as HOMO and LUMO energies, band gaps, ionization potential （IP） and electron affinity （EA） of 2,7- and 3,6-1inked carbazole trimers, two conjugated oligomcrs with different linkages of ...Electronic properties, such as HOMO and LUMO energies, band gaps, ionization potential （IP） and electron affinity （EA） of 2,7- and 3,6-1inked carbazole trimers, two conjugated oligomcrs with different linkages of carbazole, were studicd by the density functional theory with Becke-Lee-Young-Parr composite exchange correlation functional （B3LYP）. The absorption spectra of these compounds were also investigated by time-dependent density functional theory （TD-DFT） with 6-3 IG＊ basis set. The calculated results indicated that the HOMO and LUMO of the 2,7- and 3,6-1inked carbazole trimers are both slightly destabilized on going from methyl substitution to sec-butyl substitution. Both IP and EA exhibit their good hole-transporting but poor electronaccepting ability. The presence of alkyl groups on the nitrogen atoms does not affect the intra-chain electronic delocalization along the molecular frame. Thus no significant effect on the band gap and absorption spectra of compounds has been found.展开更多
文摘The structural, electronic, and optical properties of Cu2Zn1−xBaxSn1−ySiyS4 compounds have been calculated using GGA-PBE function within the framework of Density Functional Theory (DFT). In the present work, lattice parameters remained the same, that is tetragonal crystal structure for 0% and 100% doping concentration. The electronic band gap of Cu2Zn1−xBaxSn1−ySiyS4 compounds has been gradually increased for continuous increment of doping concentration where the highest electronic band gap is 1.117 eV for Cu2BaSiS4 structure. Moreover, the band gap changes from direct to indirect band gap with the increase of doping concentration in the parent compound. The absorption coefficient has been found to be high (> 104 cm−1) in UV-region for all the doping concentration which makes the studied compound as a potential candidate of absorber layer in the UV detector. The theoretical study of the effect of double doping in the CZTS compound is very interesting for improving the quality of it and it would be a reference for the theoretical and experimental researchers.
基金supported by the Natural Science Foundation of Jilin Province(No.20220101017JC)National Natural Science Foundation of China(No.11675063)Key Laboratory of Nuclear Data Foundation(JCKY2020201C157).
文摘In this study,a microscopic method for calculating the nuclear level density(NLD)based on the covariant density functional theory(CDFT)is developed.The particle-hole state density is calculated by a combinatorial method using single-particle level schemes obtained from the CDFT,and the level densities are then obtained by considering collective effects such as vibration and rotation.Our results are compared with those of other NLD models,including phenomenological,microstatisti-cal and nonrelativistic Hartree–Fock–Bogoliubov combinatorial models.This comparison suggests that the general trends among these models are essentially the same,except for some deviations among the different NLD models.In addition,the NLDs obtained using the CDFT combinatorial method with normalization are compared with experimental data,including the observed cumulative number of levels at low excitation energies and the measured NLDs.The CDFT combinatorial method yields results that are in reasonable agreement with the existing experimental data.
基金supported by the National Natural Science Foundation of China(92061125,21978294)Beijing Natural Science Foundation(Z200012)+3 种基金Jiangxi Natural Science Foundation(20212ACB213009)DNL Cooperation Fund,CAS(DNL201921)Self-deployed Projects of Ganjiang Innovation Academy,Chinese Academy of Sciences(E055B003)Hebei Natural Science Foundation(B2020103043)。
文摘Developing novel oxygen reduction reaction(ORR)catalysts with high activity is urgent for proton exchange membrane fuel cells.Herein,we investigated a group of size-dependent Pt-based catalysts as promising ORR catalysts by density functional theory calculations,ranging from single-atom,nanocluster to bulk Pt catalysts.The results showed that the ORR overpotential of these Pt-based catalysts increased when its size enlarged to the nanoparticle scale or reduced to the single-atom scale,and the Pt_(38)cluster had the lowest ORR overpotential(0.46 V)compared with that of Pt_(111)(0.57 V)and single atom Pt(0.7 V).Moreover,we established a volcano curve relationship between the ORR overpotential and binding energy of O*(ΔE_(O*),confirming the intermediate species anchored on Pt38cluster with suitable binding energy located at top of volcano curve.The interaction between intermediate species and Pt-based catalysts were also investigated by the charge distribution and projected density of state and which further confirmed the results of volcano curve.
文摘In 2014, 50 years following the introduction of density functional theory (DFT), a rigorous understanding of it was published [AIP Advances, 4, 127,104 (2014)]. This understanding includes two features that complete the theory in practice, inasmuch as they are necessary for its correct application in electronic structure calculations;this understanding elucidates what appears to have been the crucial misunderstanding for 50 years, namely, the confusion between a stationary solution, attainable with most basis sets, following self-consistent iterations, with the ground state solution. The latter is obtained by a calculation that employs the well-defined optimal basis set for the system. The aim of this work is to review the above understanding and to extend it to the relativistic generalization of density functional theory by Rajagopal and Callaway [Phys. Rev. B7, 1912 (1973)]. This extension straightforwardly follows similar steps taken in the non-relativistic case, with the four-component current density, in the former, replacing the electronic charge density, in the latter. This new understanding, which completes relativistic DFT in practice, is expected to be needed for the study of heavy atoms and of materials (from molecules to solids) containing them—as is the case for some high temperature superconductors.
基金funded by the National Natural Science Foundation of China(Nos.52174246,51864003)the Open Foundation of Key Laboratory of Green Separation and Enrichment of Strategic Metal Mineral Resources,China(No.202205AG070012)。
基金the Scientific and Technology Foundation of Fuzhou University and the Key Project of Fujian Province (2005HZ01-2-6)
文摘The plane-wave pseudopotential function method, based on density-functional theory, has been used to calculate the adsorption, electronic band structures, orbitals and optical absorption spectrum of [Fe（CN）6]^4- on TiOz anatase（101） surface. Our calculations reveal that the surface-modified anatase system has large adsorption energy and a much narrower band gap. [Fe（CN）6]^4- adsorption on the （101） surface could lead to a large red shift of the anatase optical absorption threshold, which extends into a visible region significantly. The calculated results are in agreement with the experiment and other theoretical studies reasonably. It is very important for the understanding and further development ofphotovoltaic materials that are active under visible light.
基金the State Science Foundation of China (No. 20477018)
文摘Optimized calculation of 35 dialkyl phenyl phosphate compounds （OPs） was carded out at the B3LYP/6-31G^＊ level in Gaussian 98 program. Based on the theoretical linear solvation energy relationship （TLSER） model, the obtained parameters were taken as theoretical descriptors to establish the novel QSPR model for predicting n-octanol/water partition coefficients （lgKow） of OPs. The new model achieved in this work contains three variables, i.e., molecular volume （Vm）, dipole moment of the molecules （μ） and enthalpy （H^0）. For this model, R^2 = 0.9167 and SD = 0.31 at large t values. In addition, the variation inflation factors （VIF） of variables are all close to 1.0, suggesting high accuracy of the predicting model. And the results of cross-validation test （q^2 = 0.8993） and method validation also showed the model of this study exhibited optimum stability and better predictive power than that from semi-empirical method. The model achieved can be used to predict IgKow of congeneric compounds.
基金Supported by the National Natural Science Foundation of China （20737001）.
文摘The thermodynamic properties of 135 polybrominated dibenzothiophenes （PBDTs） in the gaseous state at 298.15 K and 1.013×10^5 Pa, are calculated using the density functional theory （the B3LYP/6-311G^＊＊） with Gaussian 03. Based on these data, the isodesmic reacflons are designed to calculate the standard enthalpy of formation （△fH^θ） and the standard Gibbs energy of formation （△fG^θ） of PBDTs. The relations of these thermodynamic parameters with the number and positionof bromine subsfituents （NPBS） are discussed, and it is found that there exist good correlations between othermody namic parameters （including heat capacity at constant volume, entropy, enthaipy, free energy, △fH^θ, △fG^θ） and NPBS. Thoe relative stability order of PBDT congeners is proposed theoretically based on the relative magnitude of their △fG^θ. In addition, the values of molar heat capacities at constant pressure （Cp,m） for PBDT c ongelaers are calculated.
基金Project supported by Henan University of Technology Foundation (Grant No. 2009BS025)China Academy of Engineering Physics Foundation (Grant No. 2007B08008)
文摘This paper applies a density functional theory （DFT） and grand canonical Monte Carlo simulations （GCMC） to investigate the physisorptions of molecular hydrogen in single-walled BC3 nanotubes and carbon nanotubes. The DFT calculations may provide useful information about the nature of hydrogen adsorption and physisorption energies in selected adsorption sites of these two nanotubes. Furthermore, the GCMC simulations can reproduce their storage capacity by calculating the weight percentage of the adsorbed molecular hydrogen under different conditions. The present results have shown that with both computational methods, the hydrogen storage capacity of BC3 nanotubes is superior to that of carbon nanotubes. The reasons causing different behaviour of hydrogen storage in these two nanotubes are explained by using their contour plots of electron density and charge-density difference.
基金This work was partly supported by Innovation Foundation of the Chinese Academy of Sciences (K2003D2), National Natural Science Foundation of China (No. 20173060), Hi-tech Research and Development Program of China (2003AA517040) and Knowledge Innovation Program of the Chinese Academy of Sciences (KGCX2-SW-310)
文摘The electronic and physical properties of PtmPdn （m＋n≤5） metal clusters and their interactions with dioxygen have been studied by using hybrid density functional B3LYP method. The total energies, atomization energies, vibration frequencies, and charge distributions were reported. The Pt-Pt bridge site modified by Pd atoms was found to be the most active site for the dissociation of dioxygen, which was mainly due to the change of electronic structures of the Pt atoms in bimetallic Pt-Pd clusters.
基金the National Natural Science Foundation of China(No.20737001 and 20477018)
文摘The structural and thermodynamic （PCTAs） in the ideal gas state at 298.15 K and 1.013 properties of 75 polychlorinated thianthrenes ×10^5 Pa have been calculated at the B3LYP/6- 31G＊ level using Gaussian 98 program. Based on the output data of Gaussian, the isodesmic reactions were designed to calculate standard enthalpy of formation （△fH^θ） and standard free energy of formation （△fH^θ） of PCTAs congeners. The relations of these thermodynamic parameters with the number and position of C1 atom substitution （Npcs） were discussed, and it was found that there exists high correlation between thermodynamic parameters （total energy （TE）, zero-point vibrational energy （ZPE）, thermal correction to energy （Eth）, heat capacity at constant volume （Cv^θ）, entropy （S^θ）, enthalpy （H^θ）, free energy （G^θ）, standard enthalpies of formation （△fH^θ） and standard Gibbs energies of formation （△fG^θ）） and Npcs. On the basis of the relative magnitude of their △fG^θ, the order of relative stability of PCTA congeners was theoretically proposed. In addition, the correlations between structural parameters and Npcs were also discussed. The good correlations were found between molecular average polarizability （α）, energy of the highest occupied molecular orbital （EHOMO）, molecular volume （Vm） and Npcs, and all R^2 values are larger than 0.95. Moreover, it was supposed that the isomer groups with higher toxicity should be Tri-CTA and TCTA.
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.11202178)
文摘Based on the density functional calculations, the structural and electronic properties of the WS2/graphene heterojunction under different strains are investigated. The calculated results show that unlike the free mono-layer WS2, the monolayer WS2 in the equilibrium WS2/graphene heterojunctionis characterized by indirect band gap due to the weak van der Waals interaction. The height of the schottky barrier for the WS2/graphene heterojunction is 0.13 eV, which is lower than the conventional metal/MoS2 contact. Moreover, the band properties and height of schottky barrier for WS2/graphene heterojunction can be tuned by strain. It is found that the height of the schottky barrier can be tuned to be near zero under an in-plane compressive strain, and the band gap of the WS2 in the heterojunction is turned into a direct band gap from the indirect band gap with the increasing schottky barrier height under an in-plane tensile strain. Our calculation results may provide a potential guidance for designing and fabricating the WS2-based field effect transistors.
基金Supported by the National Basic Research Program of China (2004CB217804)National Natural Science Foundation of China (20625621)
文摘Density functional theory was applied to study the structure of Beta zeolite. A model cluster containing 41Si atoms, 1 Al atom, 70 O atoms and 29 H atoms was constructed. The model structures were optimized using the Becke＇s three-parameter hybrid method with the Lee-Yang-Parr correlation functional （B3LYP） and the 6-31G basis set applying the Gaussian03 program package. The NMR parameters were calculated to validate the rationality of the model. It was found that in the optimization models, all O-H bond lengths were in range of 0.984-0.985A^°, among which the model with O-H bond length of 0.98478A^° was more stable than the others. The ^1H and ^27Al chemical shifts of the most stable model were 4.03434 and 55.74 ppm, which were pretty consistent with Larry＇ s experimental data of 4.1 and 54 ppm. The relationship between other structure parameters and total relative electric energy has also been found. All the results exhibit that the 42 T （the total number of Si and Al atoms is 42） model has common properties of the standard of zeolite Beta.
基金This work was supported by the China Postdoctoral Science Foundation (No. 2003033486)
文摘Optimized calculation of dibenzofuran （DF） and 135 polychlorinated dibenzofurans （PCDFs） was carried out at the B3LYP/6-31G＊ level in GAUSSIAN 98 program. Based on the theoretical linear solvation energy relationship （TLSER） model, the obtained structural parameters were taken as theoretical descriptors to establish the novel quantitative structureproperty relationship （QSPR） model for predicting n-octanol/water partition coefficients （lgKow） of PCDFs. The new model of lgKow achieved in this work contains three variables： energy of the highest occupied molecular orbital （EHOMO）, the most negative atomic partial charge （q^-） and average molecular polarizability （a）, of which R^2= 0.9011 and SD = 0,17 with larger t values. In addition, the variation inflation factors （VIF） of variables in the present model are all less than 5.5, suggesting high accuracy of the lgKow model. And the results of cross-validation test （q^2 = 0.8688） and method validation also show this model exhibits optimum stability and better predictive power than semi-empirical method. At the same time, it is found that the aqueous solubility （-lgSw） has high relative correlation with constant volume molar heat capacity （Cv^0）, of which R^2 = 0.9777 and SD = 0.22. Moreover, lgKow and -lgSw values of all PCDF congeners were predicted respectively.
基金Project supported by the Science Fund from the Ministry of National Science and Technology(NST),Bangladesh。
文摘We perform the first-principles investigations of the structural,elastic,electronic,and optical properties of SrBO3(B=Cr,Fe)perovskites under pressure based on density functional theory(DFT).This is the first detailed pressure-dependent study of the physical properties for these compounds.The calculated structural parameters are consistent with the existing experimental results and slightly decrease with the application of pressure.The mechanical properties are discussed in detail and reveal that the SrCrO3 is harder than SrFeO3.Without pressure,these compounds behave like half-metals,confirmed by their band structure and density of states.Although the SrCrO3 retains its half-metallic nature under pressure,SrFeO3 becomes metallic for both up-spin and down-spin configuration.Both charge density and bond overlap population reveal the covalent nature of Cr–O bond and Fe–O bond in the studied compounds.The optical properties of SrBO3,also discussed for the first time,reveal some interesting results.
基金The project was supported by the Scientific Research Fund of Hunan Provincial Education Department (No. 05A002)the Prominent Mid-youth Science and Technology Foundation of Hunan Province (No. 04JJ1010)
文摘Electronic properties, such as HOMO and LUMO energies, band gaps, ionization potential （IP） and electron affinity （EA） of 2,7- and 3,6-1inked carbazole trimers, two conjugated oligomcrs with different linkages of carbazole, were studicd by the density functional theory with Becke-Lee-Young-Parr composite exchange correlation functional （B3LYP）. The absorption spectra of these compounds were also investigated by time-dependent density functional theory （TD-DFT） with 6-3 IG＊ basis set. The calculated results indicated that the HOMO and LUMO of the 2,7- and 3,6-1inked carbazole trimers are both slightly destabilized on going from methyl substitution to sec-butyl substitution. Both IP and EA exhibit their good hole-transporting but poor electronaccepting ability. The presence of alkyl groups on the nitrogen atoms does not affect the intra-chain electronic delocalization along the molecular frame. Thus no significant effect on the band gap and absorption spectra of compounds has been found.
