Theoretical studies of the cubic perovskite CaFeO3 are performed using the full potential linearized augmented plane-wave method with GGA+U.The calculated structural parameters are consistent with the experimental res...Theoretical studies of the cubic perovskite CaFeO3 are performed using the full potential linearized augmented plane-wave method with GGA+U.The calculated structural parameters are consistent with the experimental results.The tolerance factor reveals the cubic phase of the compound.The spin polarized electronic band structures and densities of states as well as the integer value of the magnetic moment of the unit cell(4μB)demonstrate that CaFeO_(3)is half metal.Ferromagnetism in CaFeO_(3)is due to Fe^(+4)–O^(2)–Fe^(+4)superexchange interaction.The robust properties of the compound show that with their compression up to a certain critical lattice constant,known as the robust transition lattice constant,an abrupt change in the electronic and magnetic properties occurs;the compounds lose their integer magnetic moment and become metallic.展开更多
Zinc telluride is a versatile wide band gap semiconductor used in many applications.But it has certain limitations like large dimensions and large band gaps.Introducing alkali metal to its bulk lattice(3D)can reduce i...Zinc telluride is a versatile wide band gap semiconductor used in many applications.But it has certain limitations like large dimensions and large band gaps.Introducing alkali metal to its bulk lattice(3D)can reduce its dimensions and lanthanide can produce a red shift in the energy gap by converting it into quaternary compounds.The alkali and lanthanide incorporated quaternary zinc tellurides CsLnZnTe_(3)(Ln=La,Pr,Nd and Sm)form layered crystal structure in which_(∞)^(2)[LnZnTe_(3)]-layers are separated by Cs+layer.The famous lanthanide contraction is experimental both from lattice constants and bond lengths.The calculated band gaps are 2.26,2.28,2.12,2.05 eV for CsLaZnTe_(3),CsPrZnTe_(3),CsNdZnTe_(3) and CsSmZnTe_(3),respectively.These compounds show direct band gap nature.The energy band gaps of these compounds have not been evaluated yet both experimentally and theoretically.Energy loss functions,refractive index and dielectric functions were also calculated to explore the potential applications of CsLnZnTe_(3) in optoelectronic devices.展开更多
Structural, elastic, electronic and optical properties ofzinc-chalcogenides （viz. ZnX, X = S, Se and Te） are studied in zinc-blende structure under hydrostatic pressure using the full-potential linearized augmented ...Structural, elastic, electronic and optical properties ofzinc-chalcogenides （viz. ZnX, X = S, Se and Te） are studied in zinc-blende structure under hydrostatic pressure using the full-potential linearized augmented plane wave method. Generalized gradient approximation is used for exchange correlation potentials. Pressure-dependent lattice constants and bulk moduli are obtained using the optimization method. Young＇s modulus, Poisson＇s ratio, internal strain parameter and anisotropy are also calculated. The higher values of Young＇s modulus in comparison to the bulk modulus show that these materials are hard to break. Poisson＇s ratio is computed for the first time for these materials to the best of our knowledge and its values show higher ionic contribution in these materials. Modified Becke and Johnson （mBJ） method is used to study band gaps, density of states, dielectric function and refractive index. Electronic study shows direct band gaps convert to indirect band gaps with increasing pressure in the case of ZnS and ZnTe. We compared our results with other theoretical and experimental results. Our results are far better than other theoretical results because mBJ is the best technique to treat Ⅱ-Ⅵ semiconductors.展开更多
Structural geometry, electronic band gaps, density of states, optical and mechanical properties of double perovskite halides Cs2InBiX6(X = F, Cl, Br, I) are investigated using the density functional theory. These comp...Structural geometry, electronic band gaps, density of states, optical and mechanical properties of double perovskite halides Cs2InBiX6(X = F, Cl, Br, I) are investigated using the density functional theory. These compounds possess genuine perovskite stoichiometry, evaluated using various geometry-based indices like tolerance factor, octahedral factor, and formation energy. The fundamental electronic band gaps are direct and valued in the range 0.80–2.79 e V. These compounds have narrow band gaps(except Cs2InBiX6) due to strong orbital coupling of the cations. The valence band maximum and conduction band minimum are confirmed to be essentially of In 5 s and Bi 6 p characters, respectively. The splitting of Bi 6 p bands due to strong spin-orbit coupling causes reduction in the band gaps. These compounds have large dispersion in their bands and very low carrier effective masses. The substitution of halogen atoms has great influence on the optical properties. The mechanical properties reveal that Cs2InBiX6(X = F, Cl, Br, I) satisfy the stability criteria in cubic structures.展开更多
文摘Theoretical studies of the cubic perovskite CaFeO3 are performed using the full potential linearized augmented plane-wave method with GGA+U.The calculated structural parameters are consistent with the experimental results.The tolerance factor reveals the cubic phase of the compound.The spin polarized electronic band structures and densities of states as well as the integer value of the magnetic moment of the unit cell(4μB)demonstrate that CaFeO_(3)is half metal.Ferromagnetism in CaFeO_(3)is due to Fe^(+4)–O^(2)–Fe^(+4)superexchange interaction.The robust properties of the compound show that with their compression up to a certain critical lattice constant,known as the robust transition lattice constant,an abrupt change in the electronic and magnetic properties occurs;the compounds lose their integer magnetic moment and become metallic.
基金the Deanship of Scientific Research at King Khalid University for funding this work through research groups program under grant number(RGP.2/141/43)。
文摘Zinc telluride is a versatile wide band gap semiconductor used in many applications.But it has certain limitations like large dimensions and large band gaps.Introducing alkali metal to its bulk lattice(3D)can reduce its dimensions and lanthanide can produce a red shift in the energy gap by converting it into quaternary compounds.The alkali and lanthanide incorporated quaternary zinc tellurides CsLnZnTe_(3)(Ln=La,Pr,Nd and Sm)form layered crystal structure in which_(∞)^(2)[LnZnTe_(3)]-layers are separated by Cs+layer.The famous lanthanide contraction is experimental both from lattice constants and bond lengths.The calculated band gaps are 2.26,2.28,2.12,2.05 eV for CsLaZnTe_(3),CsPrZnTe_(3),CsNdZnTe_(3) and CsSmZnTe_(3),respectively.These compounds show direct band gap nature.The energy band gaps of these compounds have not been evaluated yet both experimentally and theoretically.Energy loss functions,refractive index and dielectric functions were also calculated to explore the potential applications of CsLnZnTe_(3) in optoelectronic devices.
文摘Structural, elastic, electronic and optical properties ofzinc-chalcogenides （viz. ZnX, X = S, Se and Te） are studied in zinc-blende structure under hydrostatic pressure using the full-potential linearized augmented plane wave method. Generalized gradient approximation is used for exchange correlation potentials. Pressure-dependent lattice constants and bulk moduli are obtained using the optimization method. Young＇s modulus, Poisson＇s ratio, internal strain parameter and anisotropy are also calculated. The higher values of Young＇s modulus in comparison to the bulk modulus show that these materials are hard to break. Poisson＇s ratio is computed for the first time for these materials to the best of our knowledge and its values show higher ionic contribution in these materials. Modified Becke and Johnson （mBJ） method is used to study band gaps, density of states, dielectric function and refractive index. Electronic study shows direct band gaps convert to indirect band gaps with increasing pressure in the case of ZnS and ZnTe. We compared our results with other theoretical and experimental results. Our results are far better than other theoretical results because mBJ is the best technique to treat Ⅱ-Ⅵ semiconductors.
文摘Structural geometry, electronic band gaps, density of states, optical and mechanical properties of double perovskite halides Cs2InBiX6(X = F, Cl, Br, I) are investigated using the density functional theory. These compounds possess genuine perovskite stoichiometry, evaluated using various geometry-based indices like tolerance factor, octahedral factor, and formation energy. The fundamental electronic band gaps are direct and valued in the range 0.80–2.79 e V. These compounds have narrow band gaps(except Cs2InBiX6) due to strong orbital coupling of the cations. The valence band maximum and conduction band minimum are confirmed to be essentially of In 5 s and Bi 6 p characters, respectively. The splitting of Bi 6 p bands due to strong spin-orbit coupling causes reduction in the band gaps. These compounds have large dispersion in their bands and very low carrier effective masses. The substitution of halogen atoms has great influence on the optical properties. The mechanical properties reveal that Cs2InBiX6(X = F, Cl, Br, I) satisfy the stability criteria in cubic structures.
