[Pw_forum] different frequencies within the same q star
W. YU
yuwen_66 at yahoo.com
Fri Jan 7 04:02:57 CET 2005
Dear pw users,
I calculated the phonon mode for a simple cubic system
Cu3N at X point, the frequencies are as follows for
different q within the same q star. The difference is
relatively small,less than 0.6cm-1 for different q in
the same q star. In this case, can I safely say the
three q point give equivalent results? If so, I still
have no idea why for different q in the same star,
some of the frequencies are quite close to each other,
but some are different? For example, the first and the
seventh.
Number of q in the star = 3
List of q in the star:
1 0.000000000 0.000000000 0.500000000
2 0.500000000 0.000000000 0.000000000
3 0.000000000 0.500000000 0.000000000
Diagonalizing the dynamical matrix
q = ( 0.000000000 0.000000000 0.500000000
)
************************************************************
omega( 1) = 1.701326 [THz] = 56.750488
[cm-1]
omega( 2) = 1.701326 [THz] = 56.750488
[cm-1]
omega( 3) = 2.518668 [THz] = 84.014282
[cm-1]
omega( 4) = 3.048279 [THz] = 101.680323
[cm-1]
omega( 5) = 3.437369 [THz] = 114.659034
[cm-1]
omega( 6) = 3.437369 [THz] = 114.659034
[cm-1]
omega( 7) = 4.451716 [THz] = 148.494263
[cm-1]
omega( 8) = 4.451716 [THz] = 148.494263
[cm-1]
omega( 9) = 9.721727 [THz] = 324.284046
[cm-1]
omega(10) = 19.953855 [THz] = 665.593379
[cm-1]
omega(11) = 20.913434 [THz] = 697.601696
[cm-1]
omega(12) = 20.913434 [THz] = 697.601696
[cm-1]
************************************************************
Diagonalizing the dynamical matrix
q = ( 0.000000000 0.500000000 0.000000000
)
************************************************************
omega( 1) = 1.700992 [THz] = 56.739356
[cm-1]
omega( 2) = 1.700992 [THz] = 56.739356
[cm-1]
omega( 3) = 2.518671 [THz] = 84.014380
[cm-1]
omega( 4) = 3.048254 [THz] = 101.679485
[cm-1]
omega( 5) = 3.437367 [THz] = 114.658972
[cm-1]
omega( 6) = 3.437367 [THz] = 114.658972
[cm-1]
omega( 7) = 4.435882 [THz] = 147.966089
[cm-1]
omega( 8) = 4.435882 [THz] = 147.966089
[cm-1]
omega( 9) = 9.721788 [THz] = 324.286106
[cm-1]
omega(10) = 19.954086 [THz] = 665.601081
[cm-1]
omega(11) = 20.913595 [THz] = 697.607081
[cm-1]
omega(12) = 20.913595 [THz] = 697.607081
[cm-1]
************************************************************
Diagonalizing the dynamical matrix
q = ( 0.500000000 0.000000000 0.000000000
)
************************************************************
omega( 1) = 1.719289 [THz] = 57.349695
[cm-1]
omega( 2) = 1.719289 [THz] = 57.349695
[cm-1]
omega( 3) = 2.518665 [THz] = 84.014176
[cm-1]
omega( 4) = 3.048277 [THz] = 101.680259
[cm-1]
omega( 5) = 3.437370 [THz] = 114.659100
[cm-1]
omega( 6) = 3.437370 [THz] = 114.659100
[cm-1]
omega( 7) = 4.435697 [THz] = 147.959901
[cm-1]
omega( 8) = 4.435697 [THz] = 147.959901
[cm-1]
omega( 9) = 9.721777 [THz] = 324.285722
[cm-1]
omega(10) = 19.953888 [THz] = 665.594483
[cm-1]
omega(11) = 20.912939 [THz] = 697.585200
[cm-1]
omega(12) = 20.912939 [THz] = 697.585200
[cm-1]
************************************************************
One of the input file is as follows:
# self-consistent calculation
cat > cu3n.scf.in << EOF
&control
calculation='scf'
restart_mode='from_scratch',
prefix='cu3n',
pseudo_dir = '$PSEUDO_DIR/',
outdir='$TMP_DIR/'
/
&system
ibrav = 1, celldm(1) = 7.090, nat = 4, ntyp = 2,
ecutwfc = 75.0 ,ecutrho=450.0,
/
&electrons
conv_thr = 1.0d-8
mixing_beta = 0.7
/
ATOMIC_SPECIES
N 14.00674 N.pz-rrkjus.UPF
Cu 63.54600 Cu.pz-d-rrkjus.UPF
ATOMIC_POSITIONS alat
N 0.000000000 0.000000000 0.000000000
Cu 0.500000000 0.000000000 0.000000000
Cu 0.000000000 0.500000000 0.000000000
Cu 0.000000000 0.000000000 0.500000000
K_POINTS automatic
4 4 4 1 1 1
EOF
echo " running the scf calculation...\c"
$PW_ROOT/bin/pw.x < cu3n.scf.in > cu3n.scf.out
echo " done"
# non self-consistent calculation
cat > cu3n.nscf.in << EOF
&control
calculation='phonon'
restart_mode='from_scratch',
prefix='cu3n',
pseudo_dir = '$PSEUDO_DIR/',
outdir='$TMP_DIR/'
/
&system
ibrav = 1, celldm(1) = 7.090, nat = 4, ntyp = 2,
ecutwfc = 75.0 ,ecutrho=450.0,
/
&electrons
conv_thr = 1.0d-8 ,
/
&phonon
xqq(1) = 0.5, xqq(2) = 0.0, xqq(3) = 0.0
/
ATOMIC_SPECIES
N 14.00674 N.pz-rrkjus.UPF
Cu 63.54600 Cu.pz-d-rrkjus.UPF
ATOMIC_POSITIONS alat
N 0.000000000 0.000000000 0.000000000
Cu 0.500000000 0.000000000 0.000000000
Cu 0.000000000 0.500000000 0.000000000
Cu 0.000000000 0.000000000 0.500000000
K_POINTS automatic
4 4 4 1 1 1
EOF
echo " running the nscf calculation at
q=0.5,0.0,0.0...\c"
$PW_ROOT/bin/pw.x < cu3n.nscf.in >> cu3n.nscf.out
echo " done"
# phonon calculation
cat > cu3n.ph.in << EOF
phonons of cu3n at 0.5,0.0,0.0
&inputph
tr2_ph=1.0d-14,
prefix='cu3n',
amass(1)=14.00674,
amass(2)=63.546,
outdir='$TMP_DIR/',
fildyn='cu3n.dyn'
/
0.5 0.0 0.0
EOF
echo " running the phonon calculation at
q=0.5,0.0,0.0...\c"
$PW_ROOT/bin/ph.x < cu3n.ph.in >> cu3n.ph.out
echo " done"
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