[Pw_forum] relaxation with vc-relax

[Payam Norouzzadeh]

Dear Sonu Kumar
Thank you for your guidelines. I will test them.
Best regards,Payam Norouzzadeh

On Thu, Mar 8, 2012 at 7:11 AM, Sonu Kumar <1009ukumar at gmail.com> wrote:

> On Thu, Mar 8, 2012 at 4:11 AM, Payam Norouzzadeh <
> payam.norouzzadeh at gmail.com> wrote:
>
>> Dear QE users
>>
>> My system has 54 atoms with a BCC structure. Its primitive unit cell
>> includes 27 atoms.
>> I am trying to find its lattice constant by using vc-relax.
>> After running it several times and for more than 3 weeks still the
>> convergence thresholds are not satisfied.
>> The forces don't like to get smaller than a specific value (around 0.02).
>> Is something wrong with my input file? Please let me know your comments.
>>
>> Best regards,Payam Norouzzadeh
>>
>>
>> &CONTROL
>>   title = Eight,
>>   calculation  = "vc-relax",
>>   restart_mode = 'from_scratch' ,
>>   prefix       = "Eight",
>>   pseudo_dir   = "/...",
>>   wfcdir = '...' ,
>>   outdir = '/...',
>>   nstep =  100  ,
>>   etot_conv_thr = 1.0E-9  ,
>>   forc_conv_thr = 5.0D-5 ,
>>   max_seconds = 172800 ,
>>   dt = 100 ,
>> /
>>
>
> force and energy threshold seems to very high, especially
> the latter. reduce them.
>
>
>> &SYSTEM
>>   ibrav = 3,
>>   celldm(1)=19.622,
>>   nat  = 27,
>>   ntyp = 3,
>>   ecutwfc   = 70.D0,
>>   ecutrho   = 700.D0,
>>   occupations='smearing',
>>   smearing='gaussian',
>>   degauss=0.02,
>> /
>> &ELECTRONS
>> diagonalization = 'cg',
>>   conv_thr    = 1.D-9,
>>   mixing_beta = 0.5D0,
>> /
>>
>
> use diagonalization= david
>
>
>> &IONS
>>  ion_dynamics = 'damp' ,
>> /
>>
>
> use default bfgs algorithm for dynamics
>
>
>> &CELL
>> cell_dynamics = 'damp-w',
>> /
>>
>
> similarly, use default bfgs.
>
>>
>>
> GOOD LUCK !!
>
> SKumar
> IITD
>
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