[Pw_forum] question about the stress in relax process

[mohnish pandey]

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** ,*
> -----------------------------------------------------------------
>
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>


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