The structural,electronic and elastic properties of the M_2SiC phases were studied,where M are 3d,4d,and 5d early transition metals.The valence electron concentration(VEC) effect of Ti,V,Cr,Zr,Nb,Mo,Hf,Ta and W on the...The structural,electronic and elastic properties of the M_2SiC phases were studied,where M are 3d,4d,and 5d early transition metals.The valence electron concentration(VEC) effect of Ti,V,Cr,Zr,Nb,Mo,Hf,Ta and W on these properties was examined.The C_(44) saturates for a VEC value in surrounding of 8.5 for each serie.Hf-s,Ta-s and W-s electrons mainly contribute to the density of states at the Fermi level,and should be involved in the conduction properties.The distortion increases with increasing VEC and decreasing k_c/k_a factor except for the series M=Ti,V and Cr,where it is lower at the VEC value of 8.5(it follows a parabolic variation).The M_2SiC was characterized by a profound anisotropy for the shear planes(1010) and compressibility in the direction is higher than that along the cone except for W_2SiC,where it is lower.展开更多
The moderate-pressure elastic properties of potassium halides KX （X=F, Cl, Br） was studied theoretically using the density functional theory （DFT） with normconserving pseudopotentials method. The phase transformat...The moderate-pressure elastic properties of potassium halides KX （X=F, Cl, Br） was studied theoretically using the density functional theory （DFT） with normconserving pseudopotentials method. The phase transformation from the B1 phase （NaCl-type structure） to the denser B2 phase （CsCl-type structure） occurred at 7.7, 3.46 and 2.96 GPa for KF, KCI and KBr, respectively. The elastic stiffness coefficients and bulk modulus of these materials were calculated as function of hydrostatic pressure and compared with both the experimental and theoretical values.展开更多
文摘The structural,electronic and elastic properties of the M_2SiC phases were studied,where M are 3d,4d,and 5d early transition metals.The valence electron concentration(VEC) effect of Ti,V,Cr,Zr,Nb,Mo,Hf,Ta and W on these properties was examined.The C_(44) saturates for a VEC value in surrounding of 8.5 for each serie.Hf-s,Ta-s and W-s electrons mainly contribute to the density of states at the Fermi level,and should be involved in the conduction properties.The distortion increases with increasing VEC and decreasing k_c/k_a factor except for the series M=Ti,V and Cr,where it is lower at the VEC value of 8.5(it follows a parabolic variation).The M_2SiC was characterized by a profound anisotropy for the shear planes(1010) and compressibility in the direction is higher than that along the cone except for W_2SiC,where it is lower.
文摘The moderate-pressure elastic properties of potassium halides KX （X=F, Cl, Br） was studied theoretically using the density functional theory （DFT） with normconserving pseudopotentials method. The phase transformation from the B1 phase （NaCl-type structure） to the denser B2 phase （CsCl-type structure） occurred at 7.7, 3.46 and 2.96 GPa for KF, KCI and KBr, respectively. The elastic stiffness coefficients and bulk modulus of these materials were calculated as function of hydrostatic pressure and compared with both the experimental and theoretical values.
