Band structure and bonding properties have been investigated in terms of periodic density functional theory（DFT） method,and two-photon absorption（TPA） spectra have been simulated by two-band model for ZnGeP2 and A...Band structure and bonding properties have been investigated in terms of periodic density functional theory（DFT） method,and two-photon absorption（TPA） spectra have been simulated by two-band model for ZnGeP2 and AgGaS2 crystals.It has been predicted that the AgGaS2 crystal has a wider window of nonlinear transmission,and the laser pumping energy larger than 1.02 and 1.35 eV will lead to deleterious TPA of higher nonlinear effect for ZnGeP2 and AgGaS2 crystals,respectively.Electron origin of TPA for them is also discussed.展开更多
The elastic, thermodynamic, electronic, and optical properties of recently discovered and potentially technologically important transition metal boride NbRuB, are investigated using the density functional formalism. B...The elastic, thermodynamic, electronic, and optical properties of recently discovered and potentially technologically important transition metal boride NbRuB, are investigated using the density functional formalism. Both generalized gradient approximation （GGA） and local density approximation （LDA） are used for optimizing the geometry and for estimating various elastic moduli and constants. The optical properties of NbRuB are studied for the first time with different photon polarizations. The frequency （energy） dependence of various optical constants complement quite well the essential features of the electronic band structure calculations. Debye temperature of NbRuB is estimated from the thermodynamical study. All these theoretical estimates are compared with published results, where available, and discussed in detail. Both electronic band structure and optical conductivity reveal robust metallic characteristics. The NbRuB possesses significant elastic anisotropy. Electronic features, on the other hand, are almost isotropic in nature. The effects of electronic band structure and Debye temperature on the emergence of superconductivity are also analyzed.展开更多
The structural characteristic and electronic properties of seven WO_3 bulk polymorphs have been studied by first-principles density functional theory(DFT) calculations. Our calculation results indicate that according ...The structural characteristic and electronic properties of seven WO_3 bulk polymorphs have been studied by first-principles density functional theory(DFT) calculations. Our calculation results indicate that according to the energy of WO_3 per unit, the stability of different WO_3 systems reduces in turn in the following order: monoclinic WO_3, orthorhombic WO_3, tetragonal WO_3, triclinic WO_3, hexagonal WO_3 and cubic WO_3. And when the unit cell is distorted from the cubic framework, the alternatively long and short W–O bonds are formed, implying an improvement of bonding-antibonding splitting associated with the interactions between W and O atoms. The deformation of the WO6 octahedron enhances the stability of the system to some extent though the energy difference between various WO_3 phases is small(< 0.1 eV/per WO_3 unit). Besides, the band gap tends to enlarge accompanied with the symmetry decrease of WO_3 bulk. According to the band structures, the minimum band gaps for those WO_3 polymorphs are direct at the Γ point except for the simple cubic and hexagonal structures. In addition, for all the WO_3 phases, the compositions of the valance band maximum(VBM) and conduction band minimum(CBM) are the same, which are relative to the O 2 p and W 5 d orbitals, respectively.展开更多
The energy bands, electronic structures and relationship between structures and properties of the crystalline alkali metal azides, LiN3, α-NaN3 and KN3, are investigated at the DFT-B3LYP level. The crystalline bulks ...The energy bands, electronic structures and relationship between structures and properties of the crystalline alkali metal azides, LiN3, α-NaN3 and KN3, are investigated at the DFT-B3LYP level. The crystalline bulks are predicted to be insulator, speculated from their band gaps of ca. 0.23-0.25 a.u. and from their level frontier bands. The atomic overlaps and electron densities show that the metals and the azides are combined by ionic bonds. The crystal lattice energies, being corrected for the basis set superposition errors, are -852.30, -771.45 and - 614.78 kJ·mol-1 for LiN3, a-NaN3 and KN3 respectively. These values are similar to those by Gray’s approximate method. The frontier crystal orbital mainly consists of the atomic orbital of the terminal nitrogen of azides. The contribution of the metallic orbital to the LUMO is very small. The electron transition from the HOMO to the LUMO is difficult to occur. Hence all the alkali metal azides are expected to be insensitive explosives, according to the '展开更多
The structural stabilities and crystal evolution behaviors of the hyper stoichiometric compound ZrC_(2)(carbon rich;C/Zr> 1.0) are studied under ambient and high pressure conditions using first-principles calculati...The structural stabilities and crystal evolution behaviors of the hyper stoichiometric compound ZrC_(2)(carbon rich;C/Zr> 1.0) are studied under ambient and high pressure conditions using first-principles calculations in combination with the particle-swarm optimization algorithm.Six viable structures of ZrC_(2) in P21/c,Cmmm,Cmc2_(1),P4_(2)/nmc,Immm and P6/mmm symmetries are identified.These structures are dynamically stable as their phonon spectra have no imaginary modes at zero pressure or at the selected high-pressure points.Among them,the P21/c phase represents the ground state structure,whereas P21/c,P4_(2)/nmc,Immm and P6/mmm phases are part of the phase transition series.The phase order and critical pressures of the phase transition are determined to be approximately 300 GPa according to the equation of states and enthalpy.Furthermore,the mechanical and electronic properties are investigated.The P21/c and Cmc2_(1) phases display a semi-metal nature,whereas the P4_(2)/nmc,Immm,P6/mmm and Cmmm phases exhibit a metallic nature.Moreover,the present study reveals considerable information regarding the structural,mechanical and electronic properties of ZrC_(2),thereby providing key insights into its material properties and evaluating its behavior in practical applications.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
The connections between different physical-chemical properties in homologous molecular series are analyzed from the quantum-mechanic and the algebraic theory points of view and are explained by influence of the gage t...The connections between different physical-chemical properties in homologous molecular series are analyzed from the quantum-mechanic and the algebraic theory points of view and are explained by influence of the gage to the quantum electronic continuum. The connection between quantum and macroscopic properties of the substances is confirmed in homologous series of n-alkanes. Linear correlation between the coefficient of magnetization and energy of the highest occupied molecular orbital in homologous series of n-alkanes C2-C10 is established. The connection between diamagnetic and electronic characteristics of n-alkanes with the temperatures of the first order phase transitions （melting point） and other physical-chemical properties were discovered. The nature of interconnection between critical and diamagnetic properties of n-alkanes C2-C10 and results of previous works allow to suppose significant role of the spin interactions in electronic continuum states along the process of the first order phase transitions.展开更多
基金Supported by the National Natural Science Foundation of China (No. 20373073)the National Basic Research Program of China (No. 2007CB815307)+1 种基金the Funds of Chinese Academy of Sciences (KJCX2-YW-H01)Fujian Key Laboratory of Nanomaterials (No. 2006L2005)
文摘Band structure and bonding properties have been investigated in terms of periodic density functional theory（DFT） method,and two-photon absorption（TPA） spectra have been simulated by two-band model for ZnGeP2 and AgGaS2 crystals.It has been predicted that the AgGaS2 crystal has a wider window of nonlinear transmission,and the laser pumping energy larger than 1.02 and 1.35 eV will lead to deleterious TPA of higher nonlinear effect for ZnGeP2 and AgGaS2 crystals,respectively.Electron origin of TPA for them is also discussed.
文摘The elastic, thermodynamic, electronic, and optical properties of recently discovered and potentially technologically important transition metal boride NbRuB, are investigated using the density functional formalism. Both generalized gradient approximation （GGA） and local density approximation （LDA） are used for optimizing the geometry and for estimating various elastic moduli and constants. The optical properties of NbRuB are studied for the first time with different photon polarizations. The frequency （energy） dependence of various optical constants complement quite well the essential features of the electronic band structure calculations. Debye temperature of NbRuB is estimated from the thermodynamical study. All these theoretical estimates are compared with published results, where available, and discussed in detail. Both electronic band structure and optical conductivity reveal robust metallic characteristics. The NbRuB possesses significant elastic anisotropy. Electronic features, on the other hand, are almost isotropic in nature. The effects of electronic band structure and Debye temperature on the emergence of superconductivity are also analyzed.
基金supported by the National Natural Science Foundation of China(21563030 and 21773030)the Jiangxi Provincial Department of Education Research Fund(12698)the Independent Research Project of State Key Laboratory of Photocatalysis on Energy and Environment(2014A02)
文摘The structural characteristic and electronic properties of seven WO_3 bulk polymorphs have been studied by first-principles density functional theory(DFT) calculations. Our calculation results indicate that according to the energy of WO_3 per unit, the stability of different WO_3 systems reduces in turn in the following order: monoclinic WO_3, orthorhombic WO_3, tetragonal WO_3, triclinic WO_3, hexagonal WO_3 and cubic WO_3. And when the unit cell is distorted from the cubic framework, the alternatively long and short W–O bonds are formed, implying an improvement of bonding-antibonding splitting associated with the interactions between W and O atoms. The deformation of the WO6 octahedron enhances the stability of the system to some extent though the energy difference between various WO_3 phases is small(< 0.1 eV/per WO_3 unit). Besides, the band gap tends to enlarge accompanied with the symmetry decrease of WO_3 bulk. According to the band structures, the minimum band gaps for those WO_3 polymorphs are direct at the Γ point except for the simple cubic and hexagonal structures. In addition, for all the WO_3 phases, the compositions of the valance band maximum(VBM) and conduction band minimum(CBM) are the same, which are relative to the O 2 p and W 5 d orbitals, respectively.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 20173028)the Postdoctoral Foundation of Chinese Ministry of Education.
文摘The energy bands, electronic structures and relationship between structures and properties of the crystalline alkali metal azides, LiN3, α-NaN3 and KN3, are investigated at the DFT-B3LYP level. The crystalline bulks are predicted to be insulator, speculated from their band gaps of ca. 0.23-0.25 a.u. and from their level frontier bands. The atomic overlaps and electron densities show that the metals and the azides are combined by ionic bonds. The crystal lattice energies, being corrected for the basis set superposition errors, are -852.30, -771.45 and - 614.78 kJ·mol-1 for LiN3, a-NaN3 and KN3 respectively. These values are similar to those by Gray’s approximate method. The frontier crystal orbital mainly consists of the atomic orbital of the terminal nitrogen of azides. The contribution of the metallic orbital to the LUMO is very small. The electron transition from the HOMO to the LUMO is difficult to occur. Hence all the alkali metal azides are expected to be insensitive explosives, according to the '
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11904081 and 11975100)the Basic Research Program of Education Bureau of Henan Province,China(Grant No.20A140007)Research Initiation Fund of Henan Institute of Technology(Grant No.KQ1817)。
文摘The structural stabilities and crystal evolution behaviors of the hyper stoichiometric compound ZrC_(2)(carbon rich;C/Zr> 1.0) are studied under ambient and high pressure conditions using first-principles calculations in combination with the particle-swarm optimization algorithm.Six viable structures of ZrC_(2) in P21/c,Cmmm,Cmc2_(1),P4_(2)/nmc,Immm and P6/mmm symmetries are identified.These structures are dynamically stable as their phonon spectra have no imaginary modes at zero pressure or at the selected high-pressure points.Among them,the P21/c phase represents the ground state structure,whereas P21/c,P4_(2)/nmc,Immm and P6/mmm phases are part of the phase transition series.The phase order and critical pressures of the phase transition are determined to be approximately 300 GPa according to the equation of states and enthalpy.Furthermore,the mechanical and electronic properties are investigated.The P21/c and Cmc2_(1) phases display a semi-metal nature,whereas the P4_(2)/nmc,Immm,P6/mmm and Cmmm phases exhibit a metallic nature.Moreover,the present study reveals considerable information regarding the structural,mechanical and electronic properties of ZrC_(2),thereby providing key insights into its material properties and evaluating its behavior in practical applications.
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.
文摘The connections between different physical-chemical properties in homologous molecular series are analyzed from the quantum-mechanic and the algebraic theory points of view and are explained by influence of the gage to the quantum electronic continuum. The connection between quantum and macroscopic properties of the substances is confirmed in homologous series of n-alkanes. Linear correlation between the coefficient of magnetization and energy of the highest occupied molecular orbital in homologous series of n-alkanes C2-C10 is established. The connection between diamagnetic and electronic characteristics of n-alkanes with the temperatures of the first order phase transitions （melting point） and other physical-chemical properties were discovered. The nature of interconnection between critical and diamagnetic properties of n-alkanes C2-C10 and results of previous works allow to suppose significant role of the spin interactions in electronic continuum states along the process of the first order phase transitions.
