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maxfei

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注册: 2013-02-15
性别: GG
专业: 凝聚态物性 II ：电子结构

[求助] 计算graphene的问题

刚刚学习VASP，典型小弱。碰到一个奇怪的问题，
我在计算2X2的supercell 的时候会得到比较靠谱的能带（见附图1）

但是计算4X4的时候能带特别怪异（见附图2），不知道是啥原因，哪位大牛指导一下
以下是我的4X4文件
cd $WORK_DIR/scf-results
rm  $WORK_DIR/scf-results/*

# VASP scf input files
cat > INCAR << EOF
SYSTEM = graphene
!LORBIT=11
PREC = Accurate ! standard precision
LREAL = .FALSE.  ! real/reciprocial space projection

ISMEAR = 0
SIGMA = 0.02
IALGO=48
NBANDS=  70

EDIFF = 1E-6
ISTART = 0 !
IBRION=-1
NELMIN = 10    ! do a minimum of four electronic steps
NSW = 0       !  steps

ISPIN = 1       ! spin polarized calculation or not
LVHAR= .TRUE.

EOF

cat > POSCAR << EOF
graphene
  9.84
   1.0000000000000000 0.0000000000000000 0.0000000000000000
-0.5000000000000000 0.8660254037844387 0.0000000000000000
   0.0000000000000000 0.0000000000000000 2.0000000000000000
C
32
Direct
      0.000000000 0.000000000 0.500000000
      0.250000000 0.000000000 0.500000000
      0.500000000 0.000000000 0.500000000
      0.750000000 0.000000000 0.500000000
      0.000000000 0.250000000 0.500000000
      0.000000000 0.500000000 0.500000000
      0.000000000 0.750000000 0.500000000
      0.250000000 0.250000000 0.500000000
      0.500000000 0.250000000 0.500000000
      0.750000000 0.250000000 0.500000000
      0.250000000 0.500000000 0.500000000
      0.500000000 0.500000000 0.500000000
      0.750000000 0.500000000 0.500000000
      0.250000000 0.750000000 0.500000000
      0.500000000 0.750000000 0.500000000
      0.750000000 0.750000000 0.500000000
      0.083333333 0.166666666 0.500000000
      0.333333333 0.166666666 0.500000000
      0.583333333 0.166666666 0.500000000
      0.833333333 0.166666666 0.500000000
      0.083333333 0.416666666 0.500000000
      0.333333333 0.416666666 0.500000000
      0.583333333 0.416666666 0.500000000
      0.833333333 0.416666666 0.500000000
      0.083333333 0.666666666 0.500000000
      0.333333333 0.666666666 0.500000000
      0.583333333 0.666666666 0.500000000
      0.833333333 0.666666666 0.500000000
      0.083333333 0.916666666 0.500000000
      0.333333333 0.916666666 0.500000000
      0.583333333 0.916666666 0.500000000
      0.833333333 0.916666666 0.500000000
EOF

zcat  $PSEUDO_DIR/paw/PBE/elements/C/POTCAR.Z  >  POTCAR

cat > KPOINTS << EOF
Automatic mesh
0             ! number of k-points = 0 ->automatic generation scheme
Gamma       ! generate a Gamma centered grid
4  4  1       ! subdivisions N_1, N_2 and N_3 along recipr. l. vectors
0. 0. 0.    ! optional shift of the mesh (s_1, s_2, s_3)
EOF

$VASP_COMMAND > scf.out

rm -r $WORK_DIR/bands-results
cp -r $WORK_DIR/scf-results $WORK_DIR/bands-results
cd $WORK_DIR/bands-results

###################################################

#####################################################################

#band structure calculation

# VASP input files
cat > INCAR << EOF
SYSTEM = graphene-pt

ICHARG = 11
!LORBIT=11
NBANDS= 70

  IALGO = 48

PREC = Accurate ! standard precision
!ENCUT = 400 !
LREAL = .FALSE.  ! real/reciprocial space projection

ISMEAR = 0
SIGMA = 0.02
!The default is LMAXMIX=2.
!For the calculation of band structures within the L(S)DA+U approach
!it is strictly required to increase LMAXMIX to 4 (d elements) and 6 (f elements).
!EDIFF = 1E-6

ISTART = 1 !
IBRION=-1
NSW = 0       !  steps

EOF

cat > KPOINTS << EOF
k-points along high symmetry lines
10  ! 10 intersections
Line-mode
Reciprocal
  0.0000000  0.0000000 0.0000000 ! gamma
  0.5000000  0.0000000 0.0000000 ! M

  0.5000000  0.0000000 0.0000000 ! M
  0.3333333  0.3333333 0.0000000 ! K

  0.3333333  0.3333333 0.0000000 ! K
  0.0000000  0.0000000 0.0000000 ! gamma

2X2超原胞