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zhangjing_hust

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[交流] 【求助】DFPT计算非线性光学系数如何考虑scissor因子

请教各位大侠,利用abinit的DFPT方法计算非线性光学系数和电光张量时,如何考虑由于DFT低估带隙造成的计算误差,文献中提到可以加入scissor因子来进行修正,请问如何在计算时设置scissor因子部分?假设已知计算的DFT带隙和实验测量的带隙,那么是在计算的脚本里添加参数,还是利用计算的结果直接修正呢?不知道如何处理这个问题,请求大家帮助?

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1楼 2010-01-03 19:24:14

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zxzj05

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qasd(金币+2,VIP+0):xiexie~ 1-3 21:02
zhangjing_hust(金币+50,VIP+0):不错,多谢啦.多谢你的指点,我还要多看看说明书,有问题再向你请教. 1-3 22:28
ice_rain(金币+1,VIP+0):xiexie 1-20 12:55

在计算的脚本里添加参数,根据实验值确定scissor shift

LDA/GGA are well known to underestimate the band-gap by up to 100%. In order to get the optical spectrum and
make a realistic comparison with experiments one needs to correct for this. This can be achieved in two ways. The
scissors shift is normally chosen to be the difference between the experimental and theoretical band-gap and is used
to shift the conduction bands only. Another way in which you do not have to rely on experimental data is to
determine the self energy using the GW approach. In this case the opening of the gap due to the GW correction can
be used as scissor shift.

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2楼2010-01-03 20:48:50

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zhangjing_hust

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引用回帖:

Originally posted by zxzj05 at 2010-1-3 20:48:
在计算的脚本里添加参数,根据实验值确定scissor shift

LDA/GGA are well known to underestimate the band-gap by up to 100%. In order to get the optical spectrum and
make a realistic comparison with ...

你好,还在吗?
可是我的问题还没有解决啊,还要麻烦你,第一个问题: 我在用GW近似作计算的时候,脚本如下:
可是却没有发现输出结果中显示 E^0_gap
                                       E^GW_gap
                                       DeltaE^GW_gap
是不是我的参数bdgw4 设置有问题啊?这个4, 5是Si的例子默认的,我不知道自己的应该设为多少?其它参数也不知道有没有问题?
               kptgw4                   #k-points
               0.000 0.000 0.000 # (Gamma)
               bdgw4    4  5          # calculate GW corrections for bands from 4 to 5
第二个问题是假如用GW近似算出了E^0_gap 和  E^GW_gap怎么利用这个结果进一步在DFPT中进一步调整非线性光学系数和电光系数?多些啦!
还有请你再告诉我下你的qq好吗?我原来和你聊过天的, 现在不知道哪个是你的号码了.
# Crystalline silicon
# Calculation of the GW correction to the direct band gap in Gamma
# Dataset 1: ground state calculation
# Dataset 2: calculation of the kss file
# Dataset 3: calculation of the screening (epsilon^-1 matrix for W)
# Dataset 4: calculation of the Self-Energy matrix elements (GW corrections)

ndtset    4

kptopt 1          # Option for the automatic generation of k points
ngkpt 4 4 4       # Density of k points

# Dataset1: usual self-consistent ground-state calculation
# Definition of the k-point grid
nkpt1 14
nshiftk1 1
shiftk1 0.0 0.0 0.0
prtden1  1       # Print out density

# Dataset2: calculation of kss file
# Definition of k-points
nkpt2 14          # A set of 19 k-points containing Gamma
nshiftk2  1
shiftk2 0.0 0.0 0.0
istwfk2  19*1                   # Option needed for Gamma
iscf2 -2          # Non self-consistent calculation
getden2  -1          # Read previous density file
nband2 80
nbandkss2 400       # Number of bands to store in KSS file

# Dataset3: Calculation of the screening (epsilon^-1 matrix)
optdriver3  3       # Screening calculation
getkss3    -1    # Obtain KSS file from previous dataset
nband3    160    # Bands to be used in the screening calculation
ecutwfn3 8    # Planewaves to be used to represent the wavefunctions
ecuteps3 8    # Dimension of the screening matrix
ppmfrq3 16.7 eV  # Imaginary frequency where to calculate the screening
nshiftk3  1
shiftk3 0.0 0.0 0.0
istwfk3  19*1

# Dataset4: Calculation of the Self-Energy matrix elements (GW corrections)
optdriver4  4       # Self-Energy calculation
getkss4    -2    # Obtain KSS file from dataset 1
getscr4    -1    # Obtain SCR file from previous dataset
nband4    250    # Bands to be used in the Self-Energy calculation
ecutwfn4 10.0    # Planewaves to be used to represent the wavefunctions
ecutsigx4 12.0    # Dimension of the G sum in Sigma_x
                  # (the dimension in Sigma_c is controlled by npweps)
nkptgw4    1             # number of k-point where to calculate the GW correction
kptgw4                      # k-points
  0.000 0.000 0.000 # (Gamma)
bdgw4    16  17          # calculate GW corrections for bands from 4 to 5

nshiftk4  1
shiftk4 0.0 0.0 0.0
istwfk4  19*1

# Data common to the three different datasets

# Definition of the unit cell: fcc
acell 3*11.0072
angdeg  55.619183  55.619183  55.619183

#Definition atomic positions and types
#*************************************
  ntypat 3             # There are three types of atom
znucl 8  30  50       # The keyword "znucl" refers to the atomic number of the
                     # possible type(s) of atom. The pseudopotential(s)
                     # mentioned in the "files" file must correspond
                     # to the type(s) of atom. Here, type 1 is the Aluminum,
                     # type 2 is the Arsenic.

#Definition of the atoms
natom 10
typat 6*1 2*2 2*3
xred


               0.101055 0.399953  -0.287941
               -0.287941 0.101055 0.399953
               0.399953  -0.287941 0.101055
               0.899953 0.601055 0.212059
               0.601055 0.212059 0.899953
               0.212059 0.899953 0.601055
               0.283968 0.283968 0.283968
               0.783968 0.783968 0.783968
               0.001565 0.001565 0.001565
               0.501565 0.501565 0.501565

# Definition of the planewave basis set (at convergence 16 Rydberg 8 Hartree)
ecut 30       # Maximal kinetic energy cut-off, in Hartree

# Use only symmorphic operations
symmorphi 0

# Definition of the SCF procedure
nstep 1000       # Maximal number of SCF cycles
               # Here, we follow the prescription for bulk silicon.
tolwfr  1.0d-9

# This line added when defaults were changed (v5.3) to keep the previous, old behaviour
  iscf 5

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3楼2010-01-03 21:52:22

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