[Pw_forum] The number of bands increases with c-axial

[jchuang]

Dear all,

 

When I computed the band structure of bi-layer graphene.

I found that if I fix the displacement of two layers (3.3A) and other
parameters. Change the c-axial (celldm(3)) only.

The number of bands will be different.

 

c-axial

17.29 A    loss 3 bands

24.62 A    equals to the result from VASP (should be the correct one)

29.9 A      2 bands more than 24.62 A

33.2 A   5 bands more than 24.62 A

 

Why 29.9A and 33.2A has more bands compared to 24.62A?

For a 2D structure, greater c-axial can generate the correct result. (with
the same interlayer displacement)

Isn't it right?

 

Best regards,

J. C. Huang IAMS, Taiwan

 

================ following is my input files for 24.62 A ================

 

Scf.in

 

&control

    calculation ='scf'

    restart_mode ='from_scratch'

    pseudo_dir ='/lustre/lwork/dyyang/bin/espresso-4.0.3/pseudo/'

    outdir ='./'

    prefix ='AuC'

    disk_io='low',

    wf_collect=.TRUE.,

 /

 &system

    ibrav = 0,

    celldm(1) = 4.65217057370607,

    nat = 4,

    ntyp = 1,

    ecutwfc = 60,

    ecutrho = 600,

    occupations = "smearing",

    smearing   = 'mp'

    degauss    = 0.02

 /

 &electrons

    diagonalization='david'

    conv_thr = 1.0e-08

    mixing_beta = 0.7

 /

ATOMIC_SPECIES

  C 12.0107 C.pz-vbc.UPF

CELL_PARAMETERS (alat)

   0.991038192   0.000000000   0.000000000

  -0.495519096   0.858264250   0.000000000

   0.000000000   0.000000000  10.000581284

ATOMIC_POSITIONS (crystal)

C       -0.333333333   0.333333333   0.000000000    0   0   0

C        0.333333333  -0.333333333   0.000000000    0   0   0

C       -0.333333333   0.333333333   0.132422202    0   0   0

C        0.000000000   0.000000000   0.132422202    0   0   0

K_POINTS (automatic)

16 16 2 0 0 0

 

Band1.in

 

# self-consistent calculation

 &control

    calculation='bands',

    restart_mode='from_scratch',

    prefix='AuC',

    pseudo_dir = '/lustre/lwork/dyyang/bin/espresso-4.0.3/pseudo/',

    outdir='./'

    disk_io='low',

    wf_collect=.TRUE.,

 /

 &system

    ibrav=0

    celldm(1)=4.65217057370607,

    nat=4, ntyp=1, nosym=.T., nbnd=50,

    ecutwfc = 60,

    ecutrho = 600.0,

    occupations='smearing',

    smearing='mp',

    degauss=0.02

/

 &electrons

    diagonalization='david'

    conv_thr = 1.0e-08

    mixing_beta = 0.7

/

ATOMIC_SPECIES

  C 12.0107 C.pz-vbc.UPF

CELL_PARAMETERS (alat)

   0.991038192   0.000000000   0.000000000

  -0.495519096   0.858264250   0.000000000

   0.000000000   0.000000000  10.000581284

ATOMIC_POSITIONS (crystal)

C       -0.333333333   0.333333333   0.000000000    0   0   0

C        0.333333333  -0.333333333   0.000000000    0   0   0

C       -0.333333333   0.333333333   0.132422202    0   0   0

C        0.000000000   0.000000000   0.132422202    0   0   0

K_POINTS {crystal}

   49

  0.50000000  0.00000000  0.00000000    1

  0.46875000  0.00000000  0.00000000    2

  0.43750000  0.00000000  0.00000000    3

  0.40625000  0.00000000  0.00000000    4

  0.37500000  0.00000000  0.00000000    5

  0.34375000  0.00000000  0.00000000    6

  0.31250000  0.00000000  0.00000000    7

  0.28125000  0.00000000  0.00000000    8

  0.25000000  0.00000000  0.00000000    9

  0.21875000  0.00000000  0.00000000   10

  0.18750000  0.00000000  0.00000000   11

  0.15625000  0.00000000  0.00000000   12

  0.12500000  0.00000000  0.00000000   13

  0.09375000  0.00000000  0.00000000   14

  0.06250000  0.00000000  0.00000000   15

  0.03125000  0.00000000  0.00000000   16

  0.00000000  0.00000000  0.00000000   17

  0.02083333  0.02083333  0.00000000   18

  0.04166666  0.04166666  0.00000000   19

  0.06249999  0.06249999  0.00000000   20

  0.08333332  0.08333332  0.00000000   21

  0.10416666  0.10416666  0.00000000   22

  0.12499999  0.12499999  0.00000000   23

  0.14583332  0.14583332  0.00000000   24

  0.16666665  0.16666665  0.00000000   25

  0.18749998  0.18749998  0.00000000   26

  0.20833331  0.20833331  0.00000000   27

  0.22916664  0.22916664  0.00000000   28

  0.24999997  0.24999997  0.00000000   29

  0.27083331  0.27083331  0.00000000   30

  0.29166664  0.29166664  0.00000000   31

  0.31249997  0.31249997  0.00000000   32

  0.33333330  0.33333330  0.00000000   33

  0.34374997  0.31249997  0.00000000   34

  0.35416664  0.29166664  0.00000000   35

  0.36458331  0.27083331  0.00000000   36

  0.37499997  0.24999997  0.00000000   37

  0.38541664  0.22916664  0.00000000   38

  0.39583331  0.20833331  0.00000000   39

  0.40624998  0.18749998  0.00000000   40

  0.41666665  0.16666665  0.00000000   41

  0.42708332  0.14583332  0.00000000   42

  0.43749999  0.12499999  0.00000000   43

  0.44791666  0.10416666  0.00000000   44

  0.45833333  0.08333333  0.00000000   45

  0.46874999  0.06249999  0.00000000   46

  0.47916666  0.04166666  0.00000000   47

  0.48958333  0.02083333  0.00000000   48

  0.50000000  0.00000000  0.00000000   49

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