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1.
First-principles study of structural, elastic, and electronic properties of the B20 structure OsSi has been reported using the plane-wave pseudopotential density functional theory method. The calculated equilibrium lattice and elastic constants are in good agreement with the experimental data and other theoretical results. The dependence of the elastic constants, the aggregate elastic modulus, the deviation from the Cauchy relation, the elastic wavevelocities in different directions and the elastic anisotropy on pressure have been obtained and discussed. This could be the first quantitative theoretical prediction of the elastic properties under high pressure of OsSi compound. Moreover, the electronic structure calculations show that OsSi is a degenerate semiconductor with the gap value of 0.68 eV, which is higher than theexperimental value of 0.26 eV. The analysis of the PDOS reveals that hybridization between Os d and Si p states indicates a certain covalency of the Os-Si bonds. 相似文献
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Based on density function theory with the ultrasoft pseudopotential scheme in the frame of the local density approximation and the generalized gradient approximation, the structural, elastic, and electronic properties of carbon with P2221 phase have been systematically studied in this paper. The calculated results show that the P2221 phase of carbon is mechanically stable and dynamically stable at ambient pressure. The anisotropy studies of Young's modulus, Poisson's ratio, shear anisotropic factor, the percentage of elastic anisotropy for bulk modulus, the percentage of elastic anisotropy for shear modulus and the universal anisotropic index show that P2221 phase of carbon exhibits anisotropy. In addition, P2221 phase is an indirect semiconductor with bandgap of 3.423 eV. But, the band gap of P2221 phase for carbon increase with increasing pressure. 相似文献
4.
基于第一性原理密度泛函理论的赝势平面波方法,对Si(111)基外延稳定正交相OsSi2的能带结构、态密度以及光电特性进行了研究.研究结果表明,Si(111)基外延稳定正交相的OsSi2是一种间接带隙半导体,禁带宽度为0.625 eV;其价带主要是由硅的3s,3p态电子和锇的5d态电子构成,导带主要由锇的5d态电子与硅的3s,3p态电子构成;其静态介电函数为15.065,折射率为3.85,吸收系数最大峰值为3.9665×105cm-1.利用理论计算的能带结构和态密度研究了Si(111)基外延稳定正交相OsSi2的介电函数、折射率、吸收系数、光电导率和能量损失函数的变化规律,为Si(111)基外延OsSi2的应用提供了理论基础. 相似文献
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Structural, elastic and electronic properties of tetragonal HfO2 at applied hydrostatic pressure up to 50 GPa have been investigated using the plane-wave ultrasoft pseudopotential technique based on the first-principles density-functional theory (DFT). The calculated ground-state properties are in good agreement with previous theoretical and experimental data. Six independent elastic constants of tetragonal HfO2 have been calculated at zero pressure and high pressure. From the obtained elastic constants, the bulk, shear and Young's modulus, Poisson's coefficients, acoustic velocity and Debye temperature have been calculated at the applied pressure. Band structure shows that tetragonal HfO2 is an indirect band gap. The variation of the gap versus pressure is well fitted to a quadratic function. 相似文献
6.
TAN Jia-Jin CHENG Yan ZHU Wen-Jun GOU Qing-Quan 《理论物理通讯》2008,50(7):220-226
The lattice parameters, bulk modulus, phase transition pressure, and temperature dependencies of the elastic constants cij of CdSe are investigated by using the Cambridge Serial Total Energy Package (CASTEP) program in the frame of Density Functional Theory (DFT). It is found that the phase transitions from the ZB structure to the RS structure and from WZ structure to RS structure are 2.2 GPa and 2.8 GPa, respectively. Our results agree well with the available experimental data and other theoretical results. The aggregate elastic modulus (B, G, E, A ), the Poisson's ratio (v), the Griuneisen parameter (γ), the Debye temperature θD on pressure and temperature are also successfully obtained. 相似文献
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The lattice parameters, bulk modulus,
phase transition pressure, and temperature dependencies of the elastic
constants cij of CdSe are investigated by using the Cambridge Serial Total Energy Package (CASTEP) program in the frame of Density Functional Theory (DFT). It is found that the phase transitions from the ZB structure to the RS structure and from WZ structure to RS structure are 2.2 GPa and 2.8 GPa, respectively. Our results agree well with the available
experimental data and other theoretical results. The aggregate elastic modulus (B, G, E, A), the Poisson's ratio (υ), the Grüneisen parameter (γ), the Debye temperature ΘD on
pressure and temperature are also successfully obtained. 相似文献
8.
利用基于密度泛函理论的第一性原理方法,计算了在压力作用下CaF2的结构相变和光学性质。结果证实了CaF2的压致结构转变的顺序是从氟石结构(空间群Fm3m)转变到PbCl2型结构(空间群Pnma),然后继续转变为Ni2In型结构(空间群P63/mmc)。在Fm3m和Pnma两种结构中,电子带隙随着压力的增加而增加,而在P63/mmc结构中,带隙随着压力的增加开始下降。实验结果显示,直到210 GPa,CaF2没有发生由绝缘体到金属的转变。据此推测,CaF2的金属化压力高于300 GPa。还讨论了压力对CaF2光学性质的影响。 相似文献
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The first principles calculations based on density functional theory (DFT) are employed to investigate the mechanical properties and electronic structure of N and Ta doped TiC. The result shows that the co-doping of nitrogen and tantalum dilates the lattice constant and improves the stability of TiC. Nitrogen and tantalum can significantly enhance the elastic constants and elastic moduli of TiC. The results of B/G and C12-C44 indicate tantalum can markedly increase the ductility of TiC. The electronic structure is calculated to describe the bonding characteristic, which revealed the strong hybridization between C-p and Ta-d and between N-p and Ti-d. The hardnessis is estimated by a semi-empirical model that is based on the Mulliken overlap population and bond length. While the weakest bond takes determinative role of the hardness of materials, the addition of Ta sharply reduces the hardness of TiC. 相似文献
10.
Electronic,elastic and dynamical properties of MgSe under pressure: rocksalt and iron silicide phase
The electronic, elastic and dynamical properties of MgSe in the rocksalt (B1) and iron silicide (B28) phase and the effects of pressure on these properties are investigated using first-principles method. The calculated electronic band structure indicates that the B1 phase of MgSe presents an indirect band-gap feature and the band gaps initially increase with pressure and subsequently decrease upon compression. Remarkably, an indirect-to-direct band-gap transition has been observed at the phase transition pressure. The elastic constants, bulk modulus, shear modulus, Young’s modulus, elastic anisotropy and B/G ratio of MgSe in the B1 and B28 phase at high pressure have also been investigated. The bulk modulus, shear modulus and Young’s modulus all increase monotonously with the increasing of pressure for the B1 and B28 phase of MgSe. The calculated phonon frequencies of the B1 phase at zero pressure agree well with available theoretical results. And the transverse acoustic phonon TA(X) mode of this phase completely softening to zero at 82 GPa. The phonon curves of the B28 phase under pressure have also been successfully investigated. 相似文献
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We studied the electronic structure of the two new transition-metal carbodiimides CoNCN and NiNCN using first-principles method, which is based on density-functional theory (DFT). The density of states (DOS), the total energy of the cell and the spin magnetic moment of CoNCN and NiNCN were calculated. The calculations reveal that the compound CoNCN and NiNCN have hall-metallic properties in ferromagnetic ground state, and the spin magnetic moment per molecule is about 7.000 μB and 6.000 μB for CoNCN and NiNCN, respectively. 相似文献
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We studied the electronic structure of the two new transition-metal carbodiimides CoNCN and NiNCN using first-principles method, which is based on density-functional theory (DFT). The density of states (DOS), the total energy of the cell and the spin magnetic moment of CoNCN and NiNCN were calculated. The calculations reveal that the compound CoNCN and NiNCN havehalf-metallic properties in ferromagnetic ground state, and the spinmagnetic moment per molecule is about 7.000 μB and 6.000 μB for CoNCN and NiNCN, respectively. 相似文献
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We have investigated the structural and elastic properties
of MgB2 under high pressures using the full-potential linearized
muffin-tin orbital (FP-LMTO) scheme within the generalized gradient
approximation correction (GGA) in the frame of density functional
theory. The calculated pressure dependence of the normalized
volume is in excellent agreement with the experimental results.
At the same time the elastic constants and acoustic anisotropy
as a function of applied pressure are presented. Through the
quasi-harmonic Debye model, we also investigate the thermodynamic
properties of MgB2. 相似文献
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Abdelmadjid Bouhemadou 《Central European Journal of Physics》2009,7(4):753-761
Using First-principle calculations, we have studied the structural, electronic and elastic properties of M2TlC, with M = Ti, Zr and Hf. Geometrical optimization of the unit cell is in good agreement with the available experimental
data. The effect of high pressures, up to 20 GPa, on the lattice constants shows that the contractions are higher along the
c-axis than along the a axis. We have observed a quadratic dependence of the lattice parameters versus the applied pressure.
The band structures show that all three materials are electrical conductors. The analysis of the site and momentum projected
densities shows that bonding is due to M d-C p and M d-Tl p hybridizations. The M d-C p bonds are lower in energy and stiffer than M d-Tl p bonds. The elastic constants are calculated using the static finite strain technique. We derived the bulk and shear moduli,
Young’s modulus and Poisson’s ratio for ideal polycrystalline M2TlC aggregates. We estimated the Debye temperature of M2TlC from the average sound velocity. This is the first quantitative theoretical prediction of the elastic properties of Ti2TlC, Zr2TlC, and Hf2TlC compounds that requires experimental confirmation.
相似文献
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应用基于密度泛函理论的第一性原理,研究Mn原子掺杂在ZnS(111)表面的电子结构和磁性.对于单原子的掺杂组态,替位表面第一层的Zn原子时体系形成能最低,说明该层是最稳定的掺杂位置.体系总磁矩取决于Mn原子的局域环境.而对于双掺杂组态,当Mn与Mn之间呈短程铁磁耦合作用时体系最稳定.这可由Mn原子和近邻S原子的p-d杂化作用解释.此时,体系的居里温度估算值为469 K,明显高于室温,具有理论指导意义.Mn原子和受主半导体之间的相互作用是自旋极化产生的主要原因.计算结果表明,该掺杂材料可以很好的用来制作稀磁半导体,具有良好的应用前景. 相似文献
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Qi-Jun Liu Zheng-Tang Liu Li-Ping Feng Hao Tian Wei Zeng 《Brazilian Journal of Physics》2012,42(1-2):20-27
Structural parameters, elastic, mechanical, electronic, chemical bonding, and optical properties of tetragonal HfSiO4 have been investigated using the plane-wave ultrasoft pseudopotential technique based on the first-principles density-functional theory. The ground-state properties obtained by minimizing the total energy are in agreement with the available experimental and theoretical data. This compound is found to be mechanically stable, and we have obtained the bulk, shear, and Young's modulus; Poisson's coefficient; and Lamé's constants. We have estimated the Debye temperature of tetragonal HfSiO4 from the acoustic velocity. Electronic and chemical bonding properties have been studied. Moreover, the complex dielectric function, refractive index, extinction coefficient, absorption coefficient, energy-loss spectrum, optical reflectivity, and complex conductivity function are calculated and analyzed. 相似文献
19.
Chun-Ying Pu Xian-Chao Xun Hai-Zhen Song Fei-Wu Zhang Zhi-Wen Lu Da-Wei Zhou 《理论物理通讯》2016,65(1):92-98
Using the particle swarm optimization algorithm on crystal structure prediction,we first predict that Mg Y alloy undergoes a first-order phase transition from Cs Cl phase to P4/NMM phase at about 55 GPa with a small volume collapse of 2.63%.The dynamical stability of P4/NMM phase at 55 GPa is evaluated by the phonon spectrum calculation and the electronic structure is discussed.The elastic constants are calculated,after which the bulk moduli,shear moduli,Young's modui,and Debye temperature are derived.The brittleness/ductile behavior,and anisotropy of two phases under pressure are discussed in details.Our results show that external pressure can change the brittle behavior to ductile at10 GPa for Cs Cl phase and improve the ductility of Mg Y alloy.As pressure increases,the elastic anisotropy in shear of Cs Cl phase decreases,while that of P4/NMM phase remains nearly constant.The elastic anisotropic constructions of the directional dependences of reciprocals of bulk modulus and Young's modulus are also calculated and discussed. 相似文献
20.
FU Zhi-Jian JI Guang-Fu CHEN Xiang-Rong GOU Qing-Quan 《理论物理通讯》2009,51(6):1129-1134
The elastic constants and thermodynamic properties of diamond are investigated by using the CRYSTAL03 program. The lattice parameters, the bulk modulus, the heat capacity, the Grüneisen parameter, and the Debye temperature are obtained. The results are in good agreement with the available experimental and theoretical data. Moreover, the relationship between V/V0 and pressure, the elastic constants underhigh pressure are successfully obtained. Especially, the elastic constants of diamond under high pressure are firstly obtained theoretically. At the same time, the variations of the thermal expansion α with pressure P and temperature T are obtained systematically in the ranges of 0-870 GPa and 0-1600 K. 相似文献