[Pw_forum] Wrong degeneracy

[Shihn Lun]

Hello Baroni,

I want to check my phonon calculation with
PRL.v77.p1151.(http://prola.aps.org/abstract/PRL/v77/i6/p1151_1)

Thanks for your reply.

Shihn Lun
--
--- Stefano Baroni <baroni at sissa.it> wrote:

> 
> On Mar 2, 2005, at 2:15 PM, Shihn Lun wrote:
> 
> > Hello all,
> >
> > I want to perform a phonon calculation of bcc Te,
> but
> > always get wrong phonon frequency.
> >
> > My phonon frequency of N point (0.0 0.0 0.5).
> >      omega( 1) =       3.953933 [THz]
> >      omega( 2) =       3.953933 [THz]
> >      omega( 3) =       6.054814 [THz]
> >
> > But omega(1) and omega(2) should be different!
> 
> I do not know whether the above frequencies are
> correct or wrong. What 
> I know for sure is that there is NOTHING wrong in
> the degeneracy of the 
> two transverse frequencies at the (0,0,1/2) point of
> a cubic lattice. 
> What makes you think that they should be different?
> 
> SB
> 
> >
> > Could you give me some suggestions?
> > Thanks in advance.
> >
> > Shihn Lun.
> >
> > ------------------------------------------
> > Here is pw.x input
> > &control
> >    calculation='scf'
> >    restart_mode='from_scratch',
> >    pseudo_dir = '/home/sllee/work/Te_pwscf/',
> >    outdir='/home/sllee/work/Te_pwscf/vol22/'
> >    nstep = 100
> >    prefix='te'
> > /
> > &system
> >    ibrav= 3, celldm(1) = 6.67362382, nat=1,
> ntyp=1,
> >    ecutwfc = 44, nbnd = 27,
> >    occupations='smearing',
> > smearing='methfessel-paxton', degauss=0.02
> > /
> > &electrons
> >     diagonalization='cg'
> >     conv_thr = 1.0e-10
> >     mixing_beta = 0.7
> > /
> > ATOMIC_SPECIES
> > Te 127.60 Te.pz-bhs.UPF
> > ATOMIC_POSITIONS
> > Te 0.0 0.0 0.0
> > K_POINTS {automatic}
> > 12 12 12 0 0 0
> > --------------------------------------------
> > Here is pw.x input fot nscf calculation
> > &control
> >    calculation='phonon'
> >    restart_mode='from_scratch',
> >    pseudo_dir = '/home/sllee/work/Te_pwscf/',
> >    outdir='/home/sllee/work/Te_pwscf/vol22/'
> >    prefix='te'
> > /
> > &system
> >  ibrav=3, celldm(1) =6.472, nat=1, ntyp=1,
> >  ecutwfc = 44.0,
> >  occupations='smearing',
> smearing='methfessel-paxton',
> > degauss=0.02
> > /
> > &electrons
> > /
> > &phonon
> >    xqq(1)=0.0, xqq(2)=0.0, xqq(3)=0.5
> > /
> > ATOMIC_SPECIES
> > Te 127.60 Te.pz-bhs.UPF
> > ATOMIC_POSITIONS {crystal}
> > Te 0.0 0.0 0.0
> > K_POINTS {automatic}
> > 12 12 12  0 0 0
> >
> > --------------------------------------------
> > Here is ph.x input for phonon calculation
> >
> > phonons of te at 0.0 0.0 0.5
> >  &inputph
> >   tr2_ph=1.0d-18,
> >   prefix='te',
> >   amass(1)=127.60 ,
> >   outdir='/home/sllee/work/Te_pwscf/vol22/',
> >   fildyn='te.dyn',
> >   fildvscf='tedv',
> >  /
> > 0.0,0.0,0.5
> > ----------------------------------------------
> >
> >
> >
> > 	
> > 		
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> ---
> Stefano Baroni    ---  SISSA  &  DEMOCRITOS National
> Simulation Center
> via Beirut 2-4 34014 Trieste Grignano / [+39] 040
> 3787 406 (tel) -528 
> (fax)
> 
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> 



	
		
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