[Pw_forum] band structure of Si unit cell and supercer
Pietro Bonfa'
pietro.bonfa at fis.unipr.it
Wed Jan 22 21:36:02 CET 2014
Dear Muthu,
the Brillouin zone of your supercell is 1/2 x 1/2 x 1/2 times the
original Brillouin zone and the bands of the unit cell are now *folded*
in the new (smaller) Brillouin zone.
Hope this helps.
Bests,
Pietro Bonfa'
On 01/22/2014 07:13 PM, Muthu V wrote:
> Dear QE users
>
>
> i have run band structure calculation for Si unit cell and 2x2x2
> super-cell. as far as i know the both band structure should be same
> since 2x2x2 super-cell is = simply repeating unit cell in space twice
> all direction.
>
> but here i have different band structures and do not know why this
> occurs. below i attached input of Si unit & 2x2x2 supercell.
>
> *_input for Si 2x2x2 supercell_*
> # self-consistent calculation
> cat > si.scf.in <http://si.scf.in> << EOF
> &control
> calculation='scf'
> restart_mode='from_scratch',
> prefix='si'
> pseudo_dir = '/home/physics/Desktop/espresso-5.0.1/pseudo/',
> outdir='/home/physics/tmp/'
> /
> &system
> ibrav = 2,
> A = 10.7952 ,
> B = 10.7952 ,
> C = 10.7952 ,
> cosAB = 0 ,
> cosAC = 0 ,
> cosBC = 0 ,
> nat = 16,
> ntyp = 1,
> ecutwfc = 18.0 ,
> ecutrho = 72 ,
> occupations = 'smearing' ,
> degauss = 0.01 ,
> smearing = 'gaussian' ,
>
> /
> &ELECTRONS
> conv_thr = 1.0d-6,
> mixing_beta = 0.3,
> /
> ATOMIC_SPECIES
> Si 28.08600 Si.pz-mt_fhi.UPF
> ATOMIC_POSITIONS angstrom
> Si 0.000000000 0.000000000 0.000000000
> Si 1.349401350 1.349401350 1.349401350
> Si -2.698802700 2.698802700 0.000000000
> Si -1.349401350 4.048204050 1.349401350
> Si 0.000000000 2.698802700 2.698802700
> Si 1.349401350 4.048204050 4.048204050
> Si -2.698802700 5.397605400 2.698802700
> Si -1.349401350 6.747006750 4.048204050
> Si -2.698802700 0.000000000 2.698802700
> Si -1.349401350 1.349401350 4.048204050
> Si -5.397605400 2.698802700 2.698802700
> Si -4.048204050 4.048204050 4.048204050
> Si -2.698802700 2.698802700 5.397605400
> Si -1.349401350 4.048204050 6.747006750
> Si -5.397605400 5.397605400 5.397605400
> Si -4.048204050 6.747006750 6.747006750
> K_POINTS automatic
> 2 2 2 0 0 0
> EOF
>
> # band structure calculation along high-symmetry lines
> cat > si.band.in <http://si.band.in> << EOF
> &control
> calculation='bands'
> pseudo_dir = '/home/physics/Desktop/espresso-5.0.1/pseudo/',
> outdir='/home/physics/tmp/',
> prefix='si'
> /
> &system
> ibrav = 2,
> A = 10.7952 ,
> B = 10.7952 ,
> C = 10.7952 ,
> cosAB = 0 ,
> cosAC = 0 ,
> cosBC = 0 ,
> nat = 16,
> ntyp = 1,
> ecutwfc = 18.0 ,
> ecutrho = 72 ,
> occupations = 'smearing' ,
> degauss = 0.01 ,
> smearing = 'gaussian' ,
> nbnd = 50,
> /
> &ELECTRONS
> conv_thr = 1.0d-6 ,
> mixing_beta = 0.3 ,
> /
> ATOMIC_SPECIES
> Si 28.08600 Si.pz-mt_fhi.UPF
> ATOMIC_POSITIONS angstrom
> Si 0.000000000 0.000000000 0.000000000
> Si 1.349401350 1.349401350 1.349401350
> Si -2.698802700 2.698802700 0.000000000
> Si -1.349401350 4.048204050 1.349401350
> Si 0.000000000 2.698802700 2.698802700
> Si 1.349401350 4.048204050 4.048204050
> Si -2.698802700 5.397605400 2.698802700
> Si -1.349401350 6.747006750 4.048204050
> Si -2.698802700 0.000000000 2.698802700
> Si -1.349401350 1.349401350 4.048204050
> Si -5.397605400 2.698802700 2.698802700
> Si -4.048204050 4.048204050 4.048204050
> Si -2.698802700 2.698802700 5.397605400
> Si -1.349401350 4.048204050 6.747006750
> Si -5.397605400 5.397605400 5.397605400
> Si -4.048204050 6.747006750 6.747006750
> K_POINTS
> 36
> 0.5 0.5 0.5 1
> 0.4 0.4 0.4 2
> 0.3 0.3 0.3 3
> 0.2 0.2 0.2 4
> 0.1 0.1 0.1 5
> 0.0 0.0 0.0 6
> 0.0 0.0 0.1 7
> 0.0 0.0 0.2 8
> 0.0 0.0 0.3 9
> 0.0 0.0 0.4 10
> 0.0 0.0 0.5 11
> 0.0 0.0 0.6 12
> 0.0 0.0 0.7 13
> 0.0 0.0 0.8 14
> 0.0 0.0 0.9 15
> 0.0 0.0 1.0 16
> 0.0 0.1 1.0 17
> 0.0 0.2 1.0 18
> 0.0 0.3 1.0 19
> 0.0 0.4 1.0 20
> 0.0 0.5 1.0 21
> 0.0 0.6 1.0 22
> 0.0 0.7 1.0 23
> 0.0 0.8 1.0 24
> 0.0 0.9 1.0 25
> 0.0 1.0 1.0 26
> 0.0 0.9 0.9 27
> 0.0 0.8 0.8 28
> 0.0 0.7 0.7 29
> 0.0 0.6 0.6 30
> 0.0 0.5 0.5 31
> 0.0 0.4 0.4 32
> 0.0 0.3 0.3 33
> 0.0 0.2 0.2 34
> 0.0 0.1 0.1 35
> 0.0 0.0 0.0 36
> EOF
>
> __
> *_Si Unitcell:_*
> # self-consistent calculation
> cat > si.scf.in <http://si.scf.in> << EOF
> &control
> calculation='scf'
> restart_mode='from_scratch',
> prefix='si'
> pseudo_dir = '$PSEUDO_DIR/',
> outdir='$TMP_DIR/'
> /
> &system
> ibrav= 2,
> A = 5.397,
> B =5.397,
> C = 5.397,
> cosAB = 0 ,
> cosAC = 0 ,
> cosBC = 0 , nat= 2, ntyp= 1,
> ecutwfc =18.0, occupations = 'smearing', degauss = 0.01 smearing
> = 'gaussian' ,
> /
> &electrons
> conv_thr = 1.0d-6
> mixing_beta = 0.3
> /
> ATOMIC_SPECIES
> Si 28.086 Si.pz-vbc.UPF
> ATOMIC_POSITIONS angstrom
> Si 0.0000000000 0.0000000000 0.0000000000
> Si 1.3494013500 1.3494013500 1.3494013500
> K_POINTS automatic
> 6 6 6 0 0 0
> EOF
>
> # band structure calculation along high-symmetry lines
> cat > si.band.in <http://si.band.in> << EOF
> &control
> calculation='bands'
> pseudo_dir = '$PSEUDO_DIR/',
> outdir='$TMP_DIR/',
> prefix='si'
> /
> &system
> ibrav= 2,
> A = 5.397,
> B =5.397,
> C = 5.397,
> cosAB = 0 ,
> cosAC = 0 ,
> cosBC = 0 ,
> nat= 2, ntyp= 1,
> ecutwfc =18.0, nbnd = 28,
> /
> &electrons
> /
> ATOMIC_SPECIES
> Si 28.086 Si.pz-vbc.UPF
> ATOMIC_POSITIONS angstrom
> Si 0.0000000000 0.0000000000 0.0000000000
> Si 1.3494013500 1.3494013500 1.3494013500
> K_POINTS
> 36
> 0.5 0.5 0.5 1
> 0.4 0.4 0.4 2
> 0.3 0.3 0.3 3
> 0.2 0.2 0.2 4
> 0.1 0.1 0.1 5
> 0.0 0.0 0.0 6
> 0.0 0.0 0.1 7
> 0.0 0.0 0.2 8
> 0.0 0.0 0.3 9
> 0.0 0.0 0.4 10
> 0.0 0.0 0.5 11
> 0.0 0.0 0.6 12
> 0.0 0.0 0.7 13
> 0.0 0.0 0.8 14
> 0.0 0.0 0.9 15
> 0.0 0.0 1.0 16
> 0.0 0.1 1.0 17
> 0.0 0.2 1.0 18
> 0.0 0.3 1.0 19
> 0.0 0.4 1.0 20
> 0.0 0.5 1.0 21
> 0.0 0.6 1.0 22
> 0.0 0.7 1.0 23
> 0.0 0.8 1.0 24
> 0.0 0.9 1.0 25
> 0.0 1.0 1.0 26
> 0.0 0.9 0.9 27
> 0.0 0.8 0.8 28
> 0.0 0.7 0.7 29
> 0.0 0.6 0.6 30
> 0.0 0.5 0.5 31
> 0.0 0.4 0.4 32
> 0.0 0.3 0.3 33
> 0.0 0.2 0.2 34
> 0.0 0.1 0.1 35
> 0.0 0.0 0.0 36
> EOF
>
> *thank you
> *
>
> /*_________________________
> *//*
> Muthu.V
> Madurai Kamaraj Universit**y**/*
> */__________________________
> */
> /**/
>
>
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--
Pietro Bonfa' - PhD student
Dipartimento di Fisica e Scienze della Terra "Macedonio Melloni"
Viale delle Scienze 7A
43124 Parma - Italy
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