1.优化结构

2.计算弹模

INCAR

ENCUT = 600
EDIFF = 1e-6
ISMEAR = 0
SIGMA = 0.05
POTIM = 0.1
LCHARG = FALSE
LWAVE = FALSE
IBRION=6
ISIF=3
NFREE=4
EDIFFG = 1e-5
EDIFFG = -0.001

关键参数: 将IBRION=6;ISIF=3;NFREE=4;

弹性矩阵会直接写在OUTCAR里。

计算得到的elastic moduli 是直角坐标下的,只要在同一直角坐标下,不同取lattice,结果相同。测试过diamond的pcell和supercell。

pcell

  SYMMETRIZED ELASTIC MODULI (kBar)
 Direction    XX          YY          ZZ          XY          YZ          ZX
 --------------------------------------------------------------------------------
 XX       10531.4122   1243.9931   1243.9931      0.0000     -0.0000      0.0000
 YY        1243.9931  10531.4122   1243.9931      0.0000      0.0000      0.0000
 ZZ        1243.9931   1243.9931  10531.4122      0.0000     -0.0000      0.0000
 XY           0.0000      0.0000      0.0000   5665.1406      0.0000      0.0000
 YZ          -0.0000      0.0000     -0.0000      0.0000   5665.1406      0.0000
 ZX           0.0000      0.0000      0.0000      0.0000      0.0000   5665.1406
 --------------------------------------------------------------------------------

supercell

 TOTAL ELASTIC MODULI (kBar)
 Direction    XX          YY          ZZ          XY          YZ          ZX
 --------------------------------------------------------------------------------
 XX       10534.8952   1243.0926   1243.0926      0.0000      0.0000      0.0000
 YY        1243.0926  10534.8952   1243.0926      0.0000      0.0000     -0.0000
 ZZ        1243.0926   1243.0926  10534.8952      0.0000     -0.0000      0.0000
 XY           0.0000      0.0000      0.0000   5629.8633      0.0000     -0.0000
 YZ           0.0000      0.0000     -0.0000     -0.0000   5629.8633     -0.0000
 ZX           0.0000     -0.0000      0.0000     -0.0000     -0.0000   5629.8633
 --------------------------------------------------------------------------------

img