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[gonze@pcpm.ucl.ac.be]

Dear Tieyu Lu,

You should use mkmem 0 , so that at each time, only one k point resides
in memory. Nevertheless, the size of files on disk will not be decreased.

I was told very recently by some people in Palaiseau (Silvana Botti, Valerie 
Veniard, ...)
that one can decrease dramatically the number of k points needed 
for the optic software, by using k point grids shifted by an "unconventional"
shift, that make every k point "unique" by symmetry. They are using
shiftk 0.125 0.250 0.375 
This should be done only in the non-SCF preparation of the optic run.

Keep us informed !
Xavier
 
Quoting mailoliver@163.com:

> Dear all:
> 
> I try to calculate the optical property of BaO in b1 phase. I modify the
> input file of toptic_1.in. And I have done convergence studies for
> ecut(37.5Hatree). When I set ngkpt=15*15*15, it needs more than 10G
> memory. How can I reduce the memory demand?
> 
> best wish 
> 
> tieyu lv
> 
> my input::
> **************************************
>  ndtset 6
> 
>    iscf1  3
> #  nband1  13
>   nstep1 9999
>  kptopt1 1
>  nbdbuf1 0
>  prtden1 1   getden1 0   getwfk1 0    ! Usual file handling data
>  toldfe1 1.0d-6
> 
> #Second dataset : NSC run with large number of bands, and points in the
> IBZ
>     iscf2 -2
>    nband2  24
>    nstep2 9999
>   kptopt2  1
>   getwfk2  1   getden2 1
>   tolwfr2 1.0d-20
> 
> #Third dataset : NSC run with large number of bands, and points in the
> the full BZ
>     iscf3 -2
>    nband3  24
>    nstep3 9999
>   kptopt3  2
>   getwfk3  2   getden3 1
>  tolwfr3 1.0d-20
> 
> #Fourth dataset : ddk response function along axis 1
>    iscf4 -3
>   nband4  24
>   nstep4  1  nline4  0
>  kptopt4  2
> 
>    nqpt4  1  qpt4  0.0d0 0.0d0 0.0d0
>   rfdir4  1 0 0
>  rfelfd4  2
>  getwfk4  3
>  tolwfr4 1.0d-20
>  nbdblock4 4
>  wfoptalg4 1
> 
> #Fifth dataset : ddk response function along axis 2
>    iscf5 -3
>   nband5  24
>   nstep5  1  nline5  0
>  kptopt5  2
> 
>    nqpt5  1  qpt5  0.0d0 0.0d0 0.0d0
>   rfdir5  0 1 0
>  rfelfd5  2
>  getwfk5  3
>  tolwfr5 1.0d-20
>  nbdblock5 4
>  wfoptalg5 1
> 
>  Sixth dataset : ddk response function along axis 3
>    iscf6 -3
>   nband6  24
>   nstep6  1  nline6  0
>  kptopt6  2
> 
>    nqpt6  1  qpt6  0.0d0 0.0d0 0.0d0
>   rfdir6  0 0 1
>  rfelfd6  2
>  getwfk6  3
>  tolwfr6 1.0d-20
>  nbdblock6 4
>  wfoptalg6 1
> 
> 
> #Data common to all datasets
>  nshiftk 1
>  shiftk
>          0.0 0.0 0.0
>  ngkpt  3*15
> 
>  acell   3*1.0493241067E+01
>  amu 137.33 15.9994
>  diemac 12.0
>  ecut 37.5
>  iscf 3
>  natom  2  nbdbuf 2
>  ntypat  2
>  rprim   0 .5 .5  .5 0 .5  .5 .5 0
>  xred 3*0.00d0 3*0.5d0
>  tnons 144*0.0
>  typat  1 2
>  znucl  56 8
> 


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