[Pw_forum] question for phonon calculation
潘登
panda.deng.pan at gmail.com
Tue Apr 21 20:23:06 CEST 2009
Dear All Users,
I was going to calculating phonon frequency of MgB2 at Gamma point.But I got
the minus value at the lowest three branch.
q = ( 0.000000000 0.000000000 0.000000000 )
**************************************************************************
omega( 1) = -1.333147 [THz] = -44.469304 [cm-1]
omega( 2) = -1.333147 [THz] = -44.469304 [cm-1]
omega( 3) = -1.003834 [THz] = -33.484515 [cm-1]
omega( 4) = 9.706117 [THz] = 323.763351 [cm-1]
omega( 5) = 9.706117 [THz] = 323.763351 [cm-1]
omega( 6) = 11.666010 [THz] = 389.138778 [cm-1]
omega( 7) = 15.807885 [THz] = 527.297796 [cm-1]
omega( 8) = 15.807885 [THz] = 527.297796 [cm-1]
omega( 9) = 20.623897 [THz] = 687.943739 [cm-1]
**************************************************************************
I had already relax the lattice.And below is my inputs for scf and phonon
calculation.Any suggest and comments on how to avoid the minus values was
appreciated.
scf.in
&control
calculation = 'scf'
restart_mode='from_scratch'
prefix='MgB2',
pseudo_dir = '//Quantum-Espresso/espresso-4.0.3/pseudo/',
outdir='/tmp/'
/
&system
ibrav=4,
celldm(1)=5.8398,
celldm(3)=1.1420,
nat=3,
ntyp=2,
ecutwfc = 45.0,
ecutrho = 450.0,
occupations= 'smearing',
degauss= 0.03,
smearing= 'cold',
/
&electrons
mixing_beta = 0.7
conv_thr = 1.0d-12
/
ATOMIC_SPECIES
Mg 24.3 Mg.pw91-np-van.UPF
B 10.8 B.pw91-n-van.UPF
ATOMIC_POSITIONS
Mg 0 0 0
B 0 0.57735 0.571
B 0.5 0.28868 0.571
K_POINTS {automatic}
32 32 32 0 0 0
ph.in
MgB2
&inputph
amass(1)= 24.3,
amass(2)= 10.8,
prefix='MgB2'
tr2_ph=1.0d-25,
alpha_mix(1)=0.5,
iverbosity=1,
outdir='//tmp/',
/
0 0 0
I also wonder how to apply 'asr' to my calculation.I could not find any
option for ph.x.
Have a nice day!
Deng Pan
Nanjing University
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