[Pw_forum] the missing symmetry of bands
程迎春
yccheng.nju at gmail.com
Wed Apr 8 13:34:25 CEST 2009
Dear PWscf users,
In my recent calculation of 4H-AlN (ABCB stacking sequence), the
band symmetry seems to be missed in bands.x calculation. The output of
bands.x is as following:
**************************************************************************
xk=( 0.00000, 0.00000, 0.00000 )
double point group C_6v (6mm)
there are 9 classes and 3 irreducible representations
the character table:
E -E C2 2C3 -2C3 2C6 -2C6 3s_v 3s_d
-C2 -3s_v -3s_d
G_7 2.00 -2.00 0.00 1.00 -1.00 1.73 -1.73 0.00 0.00
G_8 2.00 -2.00 0.00 1.00 -1.00 -1.73 1.73 0.00 0.00
G_9 2.00 -2.00 0.00 -2.00 2.00 0.00 0.00 0.00 0.00
the symmetry operations in each class:
E 1
C2 -C2 2 -2
2C6 3 4
2C3 5 6
3s_v-3s_v 7 -7 9 10 -10 -9
3s_d-3s_d 8 -8 12 -11 11 -12
-E -1
-2C6 -3 -4
-2C3 -5 -6
Band symmetry, C_6v (6mm) double point group:
e( 1 - 2) = -8.01764 eV 2 --> ?
e( 3 - 4) = -7.17573 eV 2 --> ?
e( 5 - 6) = -7.13551 eV 2 --> ?
e( 7 - 8) = -5.93881 eV 2 --> ?
e( 9 - 10) = 1.12077 eV 2 --> G_7
e( 9 - 10) = 1.12077 eV 2 --> 0 G_8
e( 11 - 12) = 3.70317 eV 2 --> 0 G_7
e( 11 - 12) = 3.70317 eV 2 --> G_8
e( 13 - 14) = 3.76782 eV 2 --> ?
e( 15 - 16) = 6.34352 eV 2 --> ?
e( 17 - 18) = 6.35869 eV 2 --> G_9
e( 19 - 20) = 6.58061 eV 2 --> ?
e( 21 - 22) = 6.59473 eV 2 --> G_9
e( 23 - 24) = 6.65103 eV 2 --> ?
e( 25 - 26) = 6.66500 eV 2 --> G_9
e( 27 - 28) = 6.91040 eV 2 --> ?
e( 29 - 30) = 6.92400 eV 2 --> G_9
e( 31 - 32) = 7.00967 eV 2 --> G_7
e( 31 - 32) = 7.00967 eV 2 --> 0 G_8
e( 33 - 34) = 11.19288 eV 2 --> ?
e( 35 - 36) = 13.31415 eV 2 --> ?
e( 37 - 38) = 13.59769 eV 2 --> ?
e( 39 - 40) = 14.02975 eV 2 --> ?
e( 41 - 42) = 17.15974 eV 2 --> ?
e( 43 - 44) = 17.32327 eV 2 --> ?
e( 45 - 46) = 17.92003 eV 2 --> ?
**************************************************************************
My question are :
1. what does "?" mean in " e( 1 - 2) = -8.01764 eV 2 -->
?" ?
2. what does "0" mean in " e( 9 - 10) = 1.12077 eV 2 -->
0 G_8" ?
3. In 2H-AlN(AB stacking sequence), all the symmetries of bands are shown.
Why in 4H-AlN, it seems much more complicated.
The input files about 4H-AlN for pw.x and bands.x are as following:
scf.in
&control
title = 2h_aln,
prefix = '4h_band',
calculation = 'scf' ,
restart_mode = 'from_scratch' ,
wf_collect = .false. ,
outdir = './' ,
wfcdir = './' ,
pseudo_dir = './' ,
tstress = .true. ,
tprnfor = .true. ,
wf_collect = .true. ,
/
&SYSTEM
ibrav = 4,
celldm(1) = 5.866002785691,
celldm(3) = 3.238615289089,
nat = 8,
ntyp = 2,
ecutwfc = 80,
nbnd = 46,
nosym = .false. ,
lspinorb = .true.,
noncolin= .true.,
starting_magnetization=0.00,
/
&ELECTRONS
electron_maxstep = 100,
conv_thr = 1.D-10,
/
ATOMIC_SPECIES
N 14.00700 N.rel-pbe-rrkjus.UPF
Al 26.98200 Al.rel-pbe-rrkj.UPF
ATOMIC_POSITIONS (crystal)
N 0.000000000 0.000000000 -0.000722968
N 0.000000000 0.000000000 0.499277032
N 0.333333333 0.666666667 0.249293699
N 0.666666667 0.333333333 0.749293699
Al 0.000000000 0.000000000 0.188800277
Al 0.000000000 0.000000000 0.688800277
Al 0.333333333 0.666666667 0.437593675
Al 0.666666667 0.333333333 0.937793675
K_POINTS automatic
8 8 8 1 1 1
band.in
&control
title = 2h_aln,
prefix = '4h_band',
calculation = 'bands' ,
restart_mode = 'from_scratch' ,
wf_collect = .false. ,
outdir = './' ,
wfcdir = './' ,
pseudo_dir = './' ,
/
&SYSTEM
ibrav = 4,
celldm(1) = 5.866002785691,
celldm(3) = 3.238615289089,
nat = 8,
ntyp = 2,
ecutwfc = 80,
nbnd=46,
lspinorb = .true.,
noncolin= .true.,
starting_magnetization=0.0,
/
&ELECTRONS
electron_maxstep = 100,
conv_thr = 1.D-10,
/
ATOMIC_SPECIES
N 14.00700 N.rel-pbe-rrkjus.UPF
Al 26.98200 Al.rel-pbe-rrkj.UPF
ATOMIC_POSITIONS (crystal)
N 0.000000000 0.000000000 -0.000722968
N 0.000000000 0.000000000 0.499277032
N 0.333333333 0.666666667 0.249293699
N 0.666666667 0.333333333 0.749293699
Al 0.000000000 0.000000000 0.188800277
Al 0.000000000 0.000000000 0.688800277
Al 0.333333333 0.666666667 0.437593675
Al 0.666666667 0.333333333 0.937793675
K_POINTS
2
0.000000 0.000000 0.000000 1.00
0.000000 0.000000 0.083333 1.00
bands.in
&inputpp
prefix='4h_band'
outdir='./'
filband='spin.dat'
lsigma(3)=.true.
lsym=.true.
/
Thank you in advance!
--
Y. C. Cheng
Department of Phyics
Nanjing University
Nanjing 210093
P. R. China
Tel: 86-25-83592907
Email: yccheng.nju at gmail.com
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