[Pw_forum] question about the stress in relax process

[mohnish pandey]

Dear Wang,
                    Are you sure that this is your input file? Because the
calculation flag says it is "scf" ..Which will not definitely do the relax
calculation....

On Mon, Sep 20, 2010 at 3:32 PM, Wang Di <didi5158 at gmail.com> wrote:

> Dear Mohnish:
> I have used the 'vc-relax' process optimized the cell parameter, however,
> the result were seem to deviate from the initial value (experimental value)
> too much.The aim of the structure optimizes is for calculating the Raman
> spectra of the structure, I think the bad structure ( not coincide to the
> experiment) is hard to got the true spectra. So I don't how to deal with the
> case. According to your experience, what should I do for the next step?
>
> Thank you, dear Mohnish, for your kind help.
>
>
>
> 2010/9/20 mohnish pandey <mohnish.iitk at gmail.com>
>
> Dear Wang,
>>                     The 'relax' process optimizes the  structure within
>> given geometric constraint. It does'nt care for stress. It minimizes force
>> only in the given constraint. If you want to minimize the stress also you
>> have to do 'vc-relax' calculation, It will give you what you want.
>>
>> On Mon, Sep 20, 2010 at 11:37 AM, Wang Di <didi5158 at gmail.com> wrote:
>>
>>> Dear all
>>>
>>> I perform the relax calculate to the crystal structure. After 11 step
>>> bfgs,  the total force and total scf correction had reach to the criterion,
>>> however, the total stress was so big P=-3443.87. I have no idea about deal
>>> with the case,  could anyone give some advices? Thanks in advance.
>>>
>>> the input file
>>> : &CONTROL
>>>                  calculation = 'scf' ,
>>>                 restart_mode = 'from_scratch' ,
>>>                   wf_collect = .true. ,
>>>                       outdir = '/lustre/AIOFM/gxgu/workLCAF/5/temp/' ,
>>>                       wfcdir = '/lustre/AIOFM/gxgu/workLCAF/5/wftemp/' ,
>>>                   pseudo_dir = '/home/AIOFM/gxgu/work/NCPP/' ,
>>>                       prefix = 'LCAF' ,
>>>                etot_conv_thr = 1.0D-7 ,
>>>                forc_conv_thr = 1.0D-6 ,
>>>                        nstep = 100 ,
>>>                      tstress = .true. ,
>>>                      tprnfor = .true. ,
>>>                     dipfield = .true. ,
>>>  /
>>>  &SYSTEM
>>>                        ibrav = 4,
>>>                    celldm(1) = 9.42432151,
>>>                    celldm(3) = 1.94804220,
>>>                          nat = 18,
>>>                         ntyp = 4,
>>>                      ecutwfc = 30 ,
>>>                      ecutrho = 120 ,
>>>                        nosym = .false. ,
>>>  /
>>>  &ELECTRONS
>>>             electron_maxstep = 100,
>>>                     conv_thr = 1.0D-10 ,
>>>  /
>>> ATOMIC_SPECIES
>>>    Li    6.94100  03-Li.LDA.fhi.UPF
>>>    Al   26.98154  13-Al.LDA.fhi.UPF
>>>    Ca   40.07800  20-Ca.LDA.fhi.UPF
>>>     F   18.99840  09-F.LDA.fhi.UPF
>>> ATOMIC_POSITIONS crystal
>>>    Li      0.333333333    0.666666667    0.250000000
>>>    Li     -0.333333333   -0.666666667   -0.250000000
>>>     F      0.389997       0.045970       0.148326
>>>     F     -0.045970       0.344027       0.148326
>>>     F     -0.344027      -0.389997       0.148326
>>>     F     -0.045970      -0.389997       0.351674
>>>     F     -0.344027       0.045970       0.351674
>>>     F      0.389997       0.344027       0.351674
>>>     F     -0.389997      -0.045970      -0.148326
>>>     F      0.045970      -0.344027      -0.148326
>>>     F      0.344027       0.389997      -0.148326
>>>     F      0.045970       0.389997       0.648326
>>>     F      0.344027      -0.045970       0.648326
>>>     F     -0.389997      -0.344027       0.648326
>>>    Al      0.666666667    0.333333333    0.250000000
>>>    Al     -0.666666667   -0.333333333   -0.250000000
>>>    Ca      0.000000000    0.000000000    0.000000000
>>>    Ca      0.000000000    0.000000000    0.500000000
>>> K_POINTS automatic
>>>   16 16 16   0 0 0
>>>
>>> best regart
>>>
>>> Wang Di
>>>
>>> --
>>> -----------------------------------------------------------------
>>> *Wang Di**
>>> The Crystal Lab,*
>>> *AnHui Institute of Optics and Fine Mechanics, ***
>>> *Chinese Academy of Sciences,**
>>> No350. , Shushanhu Road, Hefei, 230031, China**,
>>> E-mail: didi5158 @gmail.ocm** ,*
>>> -----------------------------------------------------------------
>>>
>>> _______________________________________________
>>> Pw_forum mailing list
>>> Pw_forum at pwscf.org
>>> http://www.democritos.it/mailman/listinfo/pw_forum
>>>
>>>
>>
>>
>> --
>> Regards,
>> MOHNISH,
>> -----------------------------------------------------------------
>> Mohnish Pandey
>> Y6927262,5th Year dual degree student,
>> Department of Chemical Engineering,
>> IIT KANPUR, UP, INDIA
>> +919235721300
>> -----------------------------------------------------------------
>>
>> _______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
>> http://www.democritos.it/mailman/listinfo/pw_forum
>>
>>
>
>
> --
> -----------------------------------------------------------------
> *Wang Di**
> The Crystal Lab,*
> *AnHui Institute of Optics and Fine Mechanics, ***
> *Chinese Academy of Sciences,**
> No350. , Shushanhu Road, Hefei, 230031, China**,
> E-mail: didi5158 @gmail.ocm** ,*
> -----------------------------------------------------------------
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>
>


-- 
Regards,
MOHNISH,
-----------------------------------------------------------------
Mohnish Pandey
Y6927262,5th Year dual degree student,
Department of Chemical Engineering,
IIT KANPUR, UP, INDIA
+919235721300
-----------------------------------------------------------------
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