[Pw_forum] Negative frequencies in proximity to the Gamma point problem

[Isaiah Moses]

I have a structure that I supposed was well relaxed; Total force =
0.000624 and P=   -0.00.
But I still get negative frequencies.

Isn't such Forec/pressure good enough?

Comments shall be appreciated.

Isaiah

On Sat, Jul 22, 2017 at 11:24 AM, Arles V. Gil Rebaza <arvifis at gmail.com>
wrote:

> Dear Mohammad, try to relax your system using "relax" or "vc-relax"  in
> order to reduce the interatomic forces. After that use "scf" calculation
>
> Furthermore, &cell and &ions parts and forc_conv_thr tag does not work
>  for scf calculations. Please read the QE manual.
>
> Best
>
> Dr. Arles V. Gil Rebaza
> IFLP - Argentina
>
>
> El sábado, 22 de julio de 2017, Mohammad Alidoosti <m.alidoosti at gmail.com>
> escribió:
>
>>
>> Dear PWSCF users,
>>
>> I am doing phonon frequencies calculations for Graphene-oxide. In
>> proximity to the Gamma point, I get small negative frequencies. As far as I
>> know this is a known problem, I have tried to increase "forc_conv_thr" and
>> "tr2_ph" to 1.0d-6 and 1.0d-16, respectively, but it doesn't work. Is there
>> any suggestion for solving this problem?
>> Hear is the scf input file :
>> *********************************************************************
>>  &control
>>   title = GO
>>    calculation = 'scf'
>>     restart_mode = 'from_scratch'
>>     prefix = 'GO-ph'
>>     pseudo_dir = '/home/pseudo'
>>     outdir = './tmp/'
>>                       nstep  = 200 ,
>>                    tstress = .true. ,
>>                      tprnfor = .true. ,
>>                     verbosity='high',
>>                       forc_conv_thr= 1.0d-6
>>  /
>>  &system
>>     ibrav = 0
>>     nat = 12
>>     ntyp = 3
>>     ecutwfc = 80
>>     ecutrho = 400
>>     occupations = 'smearing'
>>     smearing='methfessel-paxton',
>>     degauss = 0.001
>> /
>>  &electrons
>> conv_thr= 1.0d-8
>> mixing_beta = 0.7
>>  electron_maxstep = 200,
>>  /
>>  &IONS
>> /
>> &CELL
>> cell_dofree = '2Dxy',
>> /
>> ATOMIC_SPECIES
>>   C   12.0107    C.pbe-n-kjpaw_psl.0.1.UPF
>>   O   15.999  O.pbe-n-kjpaw_psl.0.1.UPF
>>   H   1.008   H.pbe-kjpaw_psl.0.1.UPF
>> CELL_PARAMETERS (angstrom)
>>    4.990235060   0.054948389   0.000000000
>>   -2.541880421   4.219875071   0.000000000
>>    0.000000000   0.000000000  25.000000000
>>
>> ATOMIC_POSITIONS (angstrom)
>> O       -0.021826634   0.250928937   1.721705471
>> H        0.809321037   0.681392784   1.997855886
>> O       -0.031523808   1.135550155  -1.892027240
>> H        0.808877574   0.723408478  -2.168118129
>> C        0.047350145   0.017290716   0.288486347
>> C        0.032454255   1.370630042  -0.458840404
>> C       -1.237500438   2.119007372  -0.142173618
>> C       -1.224236423   3.485316018  -0.033121650
>> C        1.242549808   3.515955831  -0.028144886
>> C        1.285890831   2.150271662  -0.137183942
>> C        2.528922921   1.430926894  -0.090219298
>> C        2.544546281   0.011979550  -0.080086702
>> K_POINTS automatic
>> 15 15 1 0  0  0
>> *******************************************************************
>>
>> Thanks in advance.
>>
>> Mohammad Alidoosti
>> --
>> Institute for Research in Fundamental Sciences (IPM)
>> School of Nano-Science
>> Shahid Farbin Alley
>> Shahid Lavasani st
>> P.Code: 19538-33511
>> Tehran, Iran
>> Tel: +98 21 2310 -3070
>>
>>
>
> --
> ###--------->   Arles V.   <---------###
>
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>



-- 
Isaiah Abu Moses
Graduate Student,
Physics Department,
University of Ibadan,
Nigeria
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