Ab initio calculations are performed on the electronic, structural, elastic and optical properties of the cubic per- ovskite KCdF3. Tile Kohn Sham equations are solved by applying the full potential linearized augment...Ab initio calculations are performed on the electronic, structural, elastic and optical properties of the cubic per- ovskite KCdF3. Tile Kohn Sham equations are solved by applying the full potential linearized augmented plane wave （FP-LAPW） method. The exchange correlation effects are included through the local density approximation （LDA ）, generalized gradient approximation （GGA） and modified Becke-Johnson （mBJ） exchange potential The calculated lattice constant is in good agreement with the experimental result. The elastic properties such as elastic constants, anisotropy factor, shear modulus, Young＇s modulus and Poisson＇s ratio are calculated. KCdF3 is ductile and elastically anisotropic. The calculations of the electronic band structure, density of states （DOS） and charge density show that this compound has an indirect energy band gap （M-F） with a mixed ionic and covalent bonding. The contribution of the different bands is analyzed from the total and partial density of states curves. Optical response of the dielectric functions, optical reflectivity, absorption coefficient, real part of optical conductivity, refractive index, extinction coefficient and electron energy loss, are presented for the energy range of O-40eV. The compound KCdF3 can be used for high-frequency optical and optoelectronic devices.展开更多
The electronic structures and properties of PuO2 and Pu2O3 have been studied according to the first principles by using the all-electron projector-augmented-wave （PAW） method. The local density approximation （LDA）...The electronic structures and properties of PuO2 and Pu2O3 have been studied according to the first principles by using the all-electron projector-augmented-wave （PAW） method. The local density approximation （LDA）＋U and the generalized gradient approximation （GGA）＋U formalisms have been used to account for the strong on-site Coulomb repulsion among the localized Pu 5f electrons. We discuss how the properties of PuO2 and Pu2O3 are affected by choosing the values of U and exchange-correlation potential. Also, the oxidation reaction of Pu2O3, leading to the formation of PuO2, and its dependence on U and exchange-correlation potential have been studied. Our results show that by choosing an appropriate U it is possible to consistently describe structural, electronic, and thermodynamic properties of PuO2 and Pu2O3, which enable the modelling of the redox process involving Pu-based materials.展开更多
High-pressure structural phase transitions in PbTe are investigated by means of the first principles total energy calculations within the generalized gradient approximation （GOAl and local density approximation CLDA...High-pressure structural phase transitions in PbTe are investigated by means of the first principles total energy calculations within the generalized gradient approximation （GOAl and local density approximation CLDA） by using the density functional theory. First principle calculation shows that PbTe is stable with the NaCl-type （B1） structure under amSient conditions and transforms to the CsCl-type （B2） structure under high pressure via an intermediate phase. Two candidate structures of the intermediate phase, namely Prima and Cmcm, are chosen for total energy calculations and discussed. It indicates that the intermediate phase adopts the Pnma structure rather than the Cmcm structure, and lattice parameters of the Pnma phase calculated by using OGA and LDA are in consistent with experimental results.展开更多
First principle calculations are performed using the super cell method with pseudopotentials and plane waves based on the Density Functional Theory (DFT) for the surface structural properties at T = 0 K. Thin slabs of...First principle calculations are performed using the super cell method with pseudopotentials and plane waves based on the Density Functional Theory (DFT) for the surface structural properties at T = 0 K. Thin slabs of 7 - 13 atomic layers of the clean Nb and Ta (001) surfaces are considered and relaxations, surface energies, and work functions of the fully relaxed slabs are presented. Consistent results are obtained with the Generalized Gradient Approximation (GGA) and the Local Density Approximation (LDA) for the exchange-correlation functional and they compare well with experimental and other theoretical works.展开更多
We report a study of the electronic structure and optical properties of uranium dioxide （U02） based on the ab-initio density-functional theory and using the generalized gradient approximation. To correctly describe ...We report a study of the electronic structure and optical properties of uranium dioxide （U02） based on the ab-initio density-functional theory and using the generalized gradient approximation. To correctly describe the strong correlation between 5 f electrons of a uranium atom, we employ the on-site Hubbard U correction term and optimize the correlation parameter of the bulk uranium dioxide. Then we give the structural and electronic properties of the ground state of uranium dioxide. Based on the accurate electronic structure, we calculate the complex dielectric function of UO2 and the related optieM properties, such as reflectivity, refractive index, extinction index, energy loss spectra, and absorption coefficient.展开更多
The equilibrium crystal structure parameter and bulk modulus of the SrMoO3 perovskite has been calculated with ab-initio method based on density functional theory (DFT) using both local density approximation (LDA) and...The equilibrium crystal structure parameter and bulk modulus of the SrMoO3 perovskite has been calculated with ab-initio method based on density functional theory (DFT) using both local density approximation (LDA) and generalized gradient approximation (GGA). The corresponding total free energy along with its various components for SrMoO3 was obtained. The lattice parameter and bulk modulus calculated for SrMoO3 within LDA are 3.99 A and 143.025 GPa respectively whereas within GGA are 4.04 A and 146.14 GPa respectively, both agree well with the available experimental data. The total energy calculated within LDA and GGA is almost the same however lower results are obtained for GGA. All calculations have been carried out using ABINIT computer code.展开更多
The compressional behavior of the MgCr_2O_4 spinel has been investigated with the CASTEP code using density functional theory and planewave pseudopotential technique. We treated the exchange-correlation interaction by...The compressional behavior of the MgCr_2O_4 spinel has been investigated with the CASTEP code using density functional theory and planewave pseudopotential technique. We treated the exchange-correlation interaction by both the local density approximation(LDA) and generalized gradient approximation(GGA) with the Perdew-Burker-Ernzerhof functional. Our simulation was conducted for the pressure range of 0–19 GPa. We obtained the isothermal bulk modulus(K_T) of the MgCr_2O_4 spinel as 181.46(48) GPa(GGA; low boundary) or 216.1(11) GPa(LDA; high boundary), with its first derivative(K'_T) as 4.41(6) or 4.5(1), respectively. The oxygen parameter u is not constant but negatively correlated with P, and decreases by about 0.5–0.6% for the investigated P range. The component polyhedra have different compressibilities, increasing in the order of(O_4)_1<CrO_6<(O_4)_2<O_6<MgO_4. The Mg-O bond in the MgO_4 tetrahedron is much more compressible than the Cr-O bond in the CrO_6 octahedron.展开更多
基金Supported by UGC,New Delhi through UGC-BSR(JRF)fellowships
文摘Ab initio calculations are performed on the electronic, structural, elastic and optical properties of the cubic per- ovskite KCdF3. Tile Kohn Sham equations are solved by applying the full potential linearized augmented plane wave （FP-LAPW） method. The exchange correlation effects are included through the local density approximation （LDA ）, generalized gradient approximation （GGA） and modified Becke-Johnson （mBJ） exchange potential The calculated lattice constant is in good agreement with the experimental result. The elastic properties such as elastic constants, anisotropy factor, shear modulus, Young＇s modulus and Poisson＇s ratio are calculated. KCdF3 is ductile and elastically anisotropic. The calculations of the electronic band structure, density of states （DOS） and charge density show that this compound has an indirect energy band gap （M-F） with a mixed ionic and covalent bonding. The contribution of the different bands is analyzed from the total and partial density of states curves. Optical response of the dielectric functions, optical reflectivity, absorption coefficient, real part of optical conductivity, refractive index, extinction coefficient and electron energy loss, are presented for the energy range of O-40eV. The compound KCdF3 can be used for high-frequency optical and optoelectronic devices.
基金Project supported by the National Natural Science Foundation of China (Grant No 10604010)
文摘The electronic structures and properties of PuO2 and Pu2O3 have been studied according to the first principles by using the all-electron projector-augmented-wave （PAW） method. The local density approximation （LDA）＋U and the generalized gradient approximation （GGA）＋U formalisms have been used to account for the strong on-site Coulomb repulsion among the localized Pu 5f electrons. We discuss how the properties of PuO2 and Pu2O3 are affected by choosing the values of U and exchange-correlation potential. Also, the oxidation reaction of Pu2O3, leading to the formation of PuO2, and its dependence on U and exchange-correlation potential have been studied. Our results show that by choosing an appropriate U it is possible to consistently describe structural, electronic, and thermodynamic properties of PuO2 and Pu2O3, which enable the modelling of the redox process involving Pu-based materials.
基金Supported by the National Natural Science Foundation of China under Grant No 11474280the Chinese Academy of Sciences under Grant Nos KJCX2-SW-N20 and KJCX2-SW-N03
文摘High-pressure structural phase transitions in PbTe are investigated by means of the first principles total energy calculations within the generalized gradient approximation （GOAl and local density approximation CLDA） by using the density functional theory. First principle calculation shows that PbTe is stable with the NaCl-type （B1） structure under amSient conditions and transforms to the CsCl-type （B2） structure under high pressure via an intermediate phase. Two candidate structures of the intermediate phase, namely Prima and Cmcm, are chosen for total energy calculations and discussed. It indicates that the intermediate phase adopts the Pnma structure rather than the Cmcm structure, and lattice parameters of the Pnma phase calculated by using OGA and LDA are in consistent with experimental results.
文摘First principle calculations are performed using the super cell method with pseudopotentials and plane waves based on the Density Functional Theory (DFT) for the surface structural properties at T = 0 K. Thin slabs of 7 - 13 atomic layers of the clean Nb and Ta (001) surfaces are considered and relaxations, surface energies, and work functions of the fully relaxed slabs are presented. Consistent results are obtained with the Generalized Gradient Approximation (GGA) and the Local Density Approximation (LDA) for the exchange-correlation functional and they compare well with experimental and other theoretical works.
基金Supported by the New Century Excellent Talents in University in Ministry of Education of China under Grant No NCET-09-0867
文摘We report a study of the electronic structure and optical properties of uranium dioxide （U02） based on the ab-initio density-functional theory and using the generalized gradient approximation. To correctly describe the strong correlation between 5 f electrons of a uranium atom, we employ the on-site Hubbard U correction term and optimize the correlation parameter of the bulk uranium dioxide. Then we give the structural and electronic properties of the ground state of uranium dioxide. Based on the accurate electronic structure, we calculate the complex dielectric function of UO2 and the related optieM properties, such as reflectivity, refractive index, extinction index, energy loss spectra, and absorption coefficient.
文摘The equilibrium crystal structure parameter and bulk modulus of the SrMoO3 perovskite has been calculated with ab-initio method based on density functional theory (DFT) using both local density approximation (LDA) and generalized gradient approximation (GGA). The corresponding total free energy along with its various components for SrMoO3 was obtained. The lattice parameter and bulk modulus calculated for SrMoO3 within LDA are 3.99 A and 143.025 GPa respectively whereas within GGA are 4.04 A and 146.14 GPa respectively, both agree well with the available experimental data. The total energy calculated within LDA and GGA is almost the same however lower results are obtained for GGA. All calculations have been carried out using ABINIT computer code.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41273072 and 41440015)
文摘The compressional behavior of the MgCr_2O_4 spinel has been investigated with the CASTEP code using density functional theory and planewave pseudopotential technique. We treated the exchange-correlation interaction by both the local density approximation(LDA) and generalized gradient approximation(GGA) with the Perdew-Burker-Ernzerhof functional. Our simulation was conducted for the pressure range of 0–19 GPa. We obtained the isothermal bulk modulus(K_T) of the MgCr_2O_4 spinel as 181.46(48) GPa(GGA; low boundary) or 216.1(11) GPa(LDA; high boundary), with its first derivative(K'_T) as 4.41(6) or 4.5(1), respectively. The oxygen parameter u is not constant but negatively correlated with P, and decreases by about 0.5–0.6% for the investigated P range. The component polyhedra have different compressibilities, increasing in the order of(O_4)_1<CrO_6<(O_4)_2<O_6<MgO_4. The Mg-O bond in the MgO_4 tetrahedron is much more compressible than the Cr-O bond in the CrO_6 octahedron.
