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[lan haiping <lanhaiping@gmail.com>]

Do you ever check your gs results ?
I think the number of G  depends on  the number of planewaves you used for calculation. Therefore, it should depend on your ecut for GS calculation.

On Fri, Mar 6, 2009 at 2:15 AM, <fishzhou@gmail.com> wrote:

Dear all,

When I was doing a GW calculation on a big super cell, the number of G vectors
is too big that I cannot handle.

I found that by reducing ngkpt, toldfe, nband or nbandkss did not help too
much. Does anyone know that how I can reduce the accuracy, I mean reduce the
number of G vectors so that I can lower my computational time.

Thanks a lot

Aaron

P.S.
Below are the part of the input file and output

=======================================
ndtset 2
jdtset 1 2

# Dataset 1 : usual self-consistent calculation for ground state charge density
kptopt1   1
ngkpt1    1 1 4
nshiftk1  1
shiftk1   0.0 0.0 0.0

toldfe1  1.0d-6    # Will stop when this tolerance is achieved on total energy
prtden1  1

# Dataset 2: calculation of kss file
kptopt2   1
ngkpt2    1 1 4
nshiftk2  1
shiftk2   0.0 0.0 0.0    # This grid contains the Gamma point
istwfk2   5*1

iscf2     -2             # Non self-consistent calculation
getden2   -1             # Read previous density file
tolwfr2   1.0d-9         # Still get it converged
nband2    160

nbandkss2 192        # Number of bands in KSS file (the maximum possible)


======================================================
           ****                  26480              12.918
           ****                  26481              12.918
           ****                  26482              12.918
           ****                  26483              12.967
           ****                  26484              12.967
           ****                  26485              12.967
           ****                  26486              12.967


 Since the number of g's to be written on file
 was 0 or too large, it has been set to the max. value.,
 computed from the union of the sets of G vectors for the different k-points.
 Number of g-vectors written on file is: 26486
 Number of bands written on file is:   192

 Since the number of bands to be computed
 is less than the number of G-vectors found,
 the program will perform partial diagonalizations.

 Amount of disk space required by _STA file=  233.50 Mbytes.

 Opening file for KS structure output: gwo_DS2_KSS
 number of Gamma centered plane waves  26486
 number of Gamma centered shells  26486
 number of bands    192
 maximum angular momentum components      3
 number of symmetry operations  1 (without inversion)
  *   g( 1)=  0  0  0
  *   g( 2)=  1  0  0
  *   g( 3)= -1  0  0
  *   g( 4)=  0  1  0
  *   g( 5)=  0 -1  0
  *   g( 6)=  1  1  0
  *   g( 7)= -1  1  0
  *   g( 8)=  1 -1  0
  *   g(****)= -1  1-13
  *   g(****)=  1 -1-13
  *   g(****)= -1 -1-13
  *   g(****)=  2  0-13
  *   g(****)= -2  0-13
  *   g(****)=  0  2-13
  *   g(****)=  0 -2-13
-P-0000
-P-0000  k-point   1
-P-0000  Calculating <G|H|G'> elements
-P-0000
-P-0000  Begin partial diago for ikpt=  1              - Size of mat.=25725 - #
bnds=  192

-- 
Hai-Ping Lan 
Department of Electronics ,
Peking University , Bejing, 100871
lanhaiping@gmail.com, hplan@pku.edu.cn