sp和phonopy计算离子晶体声子谱(重庆大学物理系).ppt

Calculations of the phonon frequencies for polar materials 王锐 Institute for Structure and Function Chongqing University 2011.11.18 * Problem: NiAl Si Non-polar materials MgO Experimental polar materials The progress of calculations of Phonon dispersion of MgO 1. Using 4*4*4 supercell to calculate the short rang Force constants 2. Calculating the high frequency dielectric constants and Born effective charge SYSTEM = MgO ENCUT = 500 ISTART = 0 ICHARG = 2 ISMEAR = 0; SIGMA = 0.002 EDIFF = 1E-5 PREC = Accurate LEPSILON= .TRUE. INCAR SYSTEM Mg O 4.24096 0.5 0.5 0.0 0.0 0.5 0.5 0.5 0.0 0.5 1 1 Direct 0.0 0.0 0.0 0.5 0.5 0.5 POSCAR Though OUTCAR In a direction with the following file INPHON, FORCES, POSCAR (initial cell) , BORN INPHON In the first line, the first value is the unit conversion factor. For VASP, it may be 27.2116 *0.52918. In the second line, dielectric constant is specifed in Cartesian coordinates. The nine values correspond to the tensor elements of  xx, xy, xz, yx, yy,yz, zx, zy, and zz. The format of BORN file From the third line, Born effective charges for the independent atoms in the primitive cell have to be written in Cartesian coordinates. COMMNED: phonopy –p --nac *