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[求助]
请计算过加静水压下体系的性质的高手帮忙看看-----加压下的压电系数
祝各位五一节快乐!
下面是我计算压电系数的步骤,请各位大侠看一下(用下面的步骤重复吴志刚的那篇PRL时,得出的结果和文献的变化趋势是一样的,但是e15的大小却约等于文献结果的一半,我分别用LDA和GGA算过,但结果差不多,也改变过精度,还是不行,所以我怀疑我的计算过程有问题,所以请各位帮忙看一下):
文献中的结果:
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我计算的结果(纵坐标的负值不用管,只看大小,因为这只是与相对的方向有关):
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(下面以我计算静水压力P=8GPa时的步骤为例子说明)
一、优化原子坐标及晶格常数
INCAR:
SYSTEM = PbTiO3_p4mm
ENCUT = 800
ISTART = 0
ICHARG = 2
ISMEAR = 0; SIGMA = 0.2
NSW = 60; IBRION = 2
EDIFF = 1E-5
EDIFFG = -1E-2
ISIF = 3
POTIM = 0.2
PREC = High
LWAVE = .FALSE.
LCHARG =.FALSE.
KPOINTS:(后面采用同一个KPOINTS)
Kpoints
0
Monkhorst-pack
11 11 11
0 0 0
POSCAR:
PbTiO3_p4mm 3
1.000000000000000
3.9020000000000000 0.0000000000000000 0.0000000000000000
0.0000000000000000 3.9020000000000000 0.0000000000000000
0.0000000000000000 0.0000000000000000 4.1550000000000000
3 1 1
Direct
0.5000000000000000 0.5000000000000000 0.1131297125826391
0.5000000000000000 0.0000000000000000 0.6196488104654303
0.0000000000000000 0.5000000000000000 0.6196488104654303
0.5000000000000000 0.5000000000000000 0.5397451459032098
0.0000000000000000 0.0000000000000000 -0.0047183237261610
POTCAR:LDA (O Ti Pb)(后面采用同一个POTCAR)
结果为:
CONTCAR:
PbTiO3_p4mm 3
1.000000000000000
3.8646149601818020 0.0000000000000000 0.0000000000000000
0.0000000000000000 3.8646149601818020 0.0000000000000000
0.0000000000000000 0.0000000000000000 4.0560945114966480
O Ti Pb
3 1 1
Direct
0.5000000000000000 0.5000000000000000 0.1035077853086349
0.5000000000000000 0.0000000000000000 0.6148831221823548
0.0000000000000000 0.5000000000000000 0.6148831221823548
0.5000000000000000 0.5000000000000000 0.5451943700111713
0.0000000000000000 0.0000000000000000 0.0089857560060325
二、加静水压并优化原子位置和晶格常数
cp CONTCAR POSCAR
INCAR:
SYSTEM = PbTiO3_p4mm
ENCUT = 800
ISTART = 0
ICHARG = 2
ISMEAR = 0; SIGMA = 0.2
NSW = 60; IBRION = 2
EDIFF = 1E-5
EDIFFG = -1E-2
ISIF = 3
PSTRESS = 80
POTIM = 0.2
PREC = High
LWAVE = .FALSE.
LCHARG =.FALSE.
KPOINTS,POTCAR 同上
结果:
CONTCAR:
PbTiO3_p4mm
1.000000000000000
3.8347769794747630 0.0000000000000000 0.0000000000000000
0.0000000000000000 3.8347769794747630 0.0000000000000000
0.0000000000000000 0.0000000000000000 3.8969610358476200
O Ti Pb
3 1 1
Direct
0.5000000000000000 0.5000000000000000 0.0882145213088690
0.5000000000000000 0.0000000000000000 0.6050703395668161
0.0000000000000000 0.5000000000000000 0.6050703395668161
0.5000000000000000 0.5000000000000000 0.5550015891094247
0.0000000000000000 0.0000000000000000 0.0340973661386298
三、计算压电常数
先做一次ISIF=2的原子坐标驰豫
INCAR:
SYSTEM = PbTiO3_p4mm
ENCUT = 800
ISTART = 0
ICHARG = 2
ISMEAR = 0; SIGMA = 0.2
NSW = 60; IBRION = 2
EDIFF = 1E-5
EDIFFG = -1E-2
ISIF = 2
PSTRESS = 80
POTIM = 0.2
PREC = High
LWAVE = .FALSE.
LCHARG =.FALSE.
再计算压电常数
CP CONTCAR POSCAR
INCAR:
SYSTEM = PbTiO3_p4mm
ENCUT = 800
LEPSILON=.TRUE.
IBRION= 8
PSTRESS= 80
ISTART = 0
ICHARG = 2
PREC = High
LWAVE = .FALSE.
LCHARG =.FALSE.
KPOINTS,POTCAR同上
结果:
e33 = 7.4546 e15 = 9.88125
文献结果:e33约等于8, e15约等于50
也就是说e33的值和文献差不多,但e15数值差很大
(另外,我去掉上一个INCAR中的PSTRESS= 80,计算结果一样)
(去掉PREC = High,用ENCUT =1200计算,结果也差不多)
(我改用GGA计算过,结果也没变多少)
各位高手,您看上面的步骤中我有没有用错参数的地方?
[ Last edited by donggaomin on 2011-5-1 at 10:52 ] |
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