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[Aaron Zhou <fishzhou@gmail.com>]

The ecut I was using is 12 hartree, which is already very small...you
mean that the number of g vectors ONLY depend on ecut?

On Thu, Mar 5, 2009 at 2:01 PM, lan haiping <lanhaiping@gmail.com> wrote:
>
> 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.
> - Show quoted text -
> 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
>