The plane wave pseudo-potential method was used to investigate the structural, electronic, and elastic properties of Cd Se_（1-x）Te_x in the zinc blende phase. It is observed that the electronic properties are improv...The plane wave pseudo-potential method was used to investigate the structural, electronic, and elastic properties of Cd Se_（1-x）Te_x in the zinc blende phase. It is observed that the electronic properties are improved considerably by using LDA ＋ U as compared to the LDA approach. The calculated lattice constants and bulk moduli are also comparable to the experimental results. The cohesive energies for pure Cd Se and Cd Te binary and their mixed alloys are calculated. The second-order elastic constants are also calculated by the Lagrangian theory of elasticity. The elastic properties show that the studied material has a ductile nature.展开更多
Using the linear-response method, we investigate the phonon properties of β-cristobalite crystal under electronic ex- citation effect. We find that the transverse-acoustic phonon frequency becomes imaginary as the el...Using the linear-response method, we investigate the phonon properties of β-cristobalite crystal under electronic ex- citation effect. We find that the transverse-acoustic phonon frequency becomes imaginary as the electron temperature is increased, which means that the lattice of β-cristobalite becomes unstable under intense laser irradiation. In addition, for the optic phonon mode, the LO（H）-TO（H） splitting disappears when the electronic temperature reaches a certain value, corresponding to the whole transverse-acoustic phonon branches becoming negative. It means that the electronic excitation destroys the macroscopic electric field of β-cristobalite. Based on the calculated phonon band structures, some thermo- dynamic properties are calculated as a function of temperature at different electronic temperatures. These investigations provide evidence that non-thermal melting takes place during a femtosecond pulse laser interaction with β-cristobalite.展开更多
In this article, density functional theory（DFT） based on generalized gradient approximation（GGA）and GGACU, U is Hubbard term, is used to study the electronic properties of CdS doped with different dopants（Cr, Mn...In this article, density functional theory（DFT） based on generalized gradient approximation（GGA）and GGACU, U is Hubbard term, is used to study the electronic properties of CdS doped with different dopants（Cr, Mn）. The calculations are carried out for Mn-doped CdS, Cr-doped CdS, and co-doping of Mn/Cr in CdS simultaneously. It is found that hopping of electrons is possible with Cr：CdS and Mn：Cr：CdS while Mn：CdS does not allow the hopping of electrons. Moreover, double exchange interactions are observed in Cr：CdS and d-d superexchange interactions are observed in Mn：CdS. Now the problem becomes interesting when one magnetic ion（Cr） supporting double exchange interactions and another ion（Mn） supporting d-d super-exchange interactions are doped simultaneously in the same system（CdS）. The co-doped CdS is more stable even at high Curie temperature due to p-d double exchange interactions and d-d super exchange interactions. Furthermore, the Cr-3d and Mn-3d states present in-between the band gap are responsible for inner shell transitions and hence for optical properties.Therefore, the co-doped system is taken into account to enhance its applications in the field of spintronic and magneto-optical devices.展开更多
The structural, electronic, and elastic properties of ZnSe1-xSx for the zinc blende structures have been studied by using the density functional theory. The calculations were performed using the plane wave pseudopoten...The structural, electronic, and elastic properties of ZnSe1-xSx for the zinc blende structures have been studied by using the density functional theory. The calculations were performed using the plane wave pseudopotential method, as implemented in Quantum ESPRESSO. The exchange-correlation potential is treated with the local density approximation pz-LDA for these properties. Moreover, LDA＋U approximation is employed to treat the ＂d＂ orbital electrons properly. A comparative study of the band gap calculated within both LDA and LDA＋U schemes is presented. The analysis of results show considerable improvement in the calculation of band gap. The inclusion of compositional disorder increases the values of all elastic constants. In this study, it is found that elastic constants C11, C12, and C44 are mainly influenced by the compositional disorder. The obtained results are in good agreement with literature.展开更多
文摘The plane wave pseudo-potential method was used to investigate the structural, electronic, and elastic properties of Cd Se_（1-x）Te_x in the zinc blende phase. It is observed that the electronic properties are improved considerably by using LDA ＋ U as compared to the LDA approach. The calculated lattice constants and bulk moduli are also comparable to the experimental results. The cohesive energies for pure Cd Se and Cd Te binary and their mixed alloys are calculated. The second-order elastic constants are also calculated by the Lagrangian theory of elasticity. The elastic properties show that the studied material has a ductile nature.
基金support by the National Natural Science Foundation of China(Grant Nos.11374217 and 11547158)
文摘Using the linear-response method, we investigate the phonon properties of β-cristobalite crystal under electronic ex- citation effect. We find that the transverse-acoustic phonon frequency becomes imaginary as the electron temperature is increased, which means that the lattice of β-cristobalite becomes unstable under intense laser irradiation. In addition, for the optic phonon mode, the LO（H）-TO（H） splitting disappears when the electronic temperature reaches a certain value, corresponding to the whole transverse-acoustic phonon branches becoming negative. It means that the electronic excitation destroys the macroscopic electric field of β-cristobalite. Based on the calculated phonon band structures, some thermo- dynamic properties are calculated as a function of temperature at different electronic temperatures. These investigations provide evidence that non-thermal melting takes place during a femtosecond pulse laser interaction with β-cristobalite.
文摘In this article, density functional theory（DFT） based on generalized gradient approximation（GGA）and GGACU, U is Hubbard term, is used to study the electronic properties of CdS doped with different dopants（Cr, Mn）. The calculations are carried out for Mn-doped CdS, Cr-doped CdS, and co-doping of Mn/Cr in CdS simultaneously. It is found that hopping of electrons is possible with Cr：CdS and Mn：Cr：CdS while Mn：CdS does not allow the hopping of electrons. Moreover, double exchange interactions are observed in Cr：CdS and d-d superexchange interactions are observed in Mn：CdS. Now the problem becomes interesting when one magnetic ion（Cr） supporting double exchange interactions and another ion（Mn） supporting d-d super-exchange interactions are doped simultaneously in the same system（CdS）. The co-doped CdS is more stable even at high Curie temperature due to p-d double exchange interactions and d-d super exchange interactions. Furthermore, the Cr-3d and Mn-3d states present in-between the band gap are responsible for inner shell transitions and hence for optical properties.Therefore, the co-doped system is taken into account to enhance its applications in the field of spintronic and magneto-optical devices.
文摘The structural, electronic, and elastic properties of ZnSe1-xSx for the zinc blende structures have been studied by using the density functional theory. The calculations were performed using the plane wave pseudopotential method, as implemented in Quantum ESPRESSO. The exchange-correlation potential is treated with the local density approximation pz-LDA for these properties. Moreover, LDA＋U approximation is employed to treat the ＂d＂ orbital electrons properly. A comparative study of the band gap calculated within both LDA and LDA＋U schemes is presented. The analysis of results show considerable improvement in the calculation of band gap. The inclusion of compositional disorder increases the values of all elastic constants. In this study, it is found that elastic constants C11, C12, and C44 are mainly influenced by the compositional disorder. The obtained results are in good agreement with literature.
