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happyzyf

铜虫 (小有名气)

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虫号: 1259643
注册: 2011-04-09
性别: MM
专业: 凝聚态物性 II ：电子结构

[求助] vasp手册GW计算Si带隙有问题已有1人参与

各位高手，

我最近根据vasp手册里面的GW计算Si的带隙的例子（http://cms.mpi.univie.ac.at/wiki/index.php/Bandgap_of_Si_in_GW）做计算，结果发现我计算出来的Si的HOMO=156.8865 eV，而LUMO=142.2128 eV，OUTCAR中费米能级的位置在144.9269 eV。

[iklhrd]$ ./gap_GW.sh OUTCAR
HOMO: band: 4 E= 156.8865
LUMO: band: 5 E= 142.2128

这里HOMO比LUMO要高，这样的话，说明是金属性质啊

我是用的例子里面的输入文件，到底是哪里的问题呢？

三步的INCAR分别是

1groundstate.dft

ISMEAR =  0
SIGMA  =  0.05
EDIFF  = 1E-8
ALGO = Very_Fast

2DFT.virtual.orbitals

# Frequency dependent dielectric tensor without
# local field effects
ALGO = Exact
NBANDS  = 64
LOPTICS = .TRUE. ; CSHIFT = 0.1
NEDOS = 2000
# you might try
#LPEAD = .TRUE.

ISMEAR =  0
SIGMA  =  0.05
EDIFF  = 1E-8

3GW

# Frequency dependent dielectric tensor including
# local field effects within the RPA (default) or
# including changes in the DFT xc-potential (LRPA=.FALSE.).
# N.B.: beware one first has to have done a
# calculation with ALGO=Exact, LOPTICS=.TRUE.
# and a reasonable number of virtual states (see above)
ALGO = GW0 ; LSPECTRAL = .TRUE. ; NOMEGA = 50

# be sure to take the same number of bands as for
# the LOPTICS=.TRUE. calculation, otherwise the
# WAVEDER file is not read correctly
NBANDS = 64

# Add this to update the quasiparticle energies
# in the Green's function (GW0)
#NELM = 4

ISMEAR =  0
SIGMA  =  0.05
EDIFF  = 1E-8

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