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[lbo@ustc.edu]

Dear all,

I am calculating the real and imaginary parts of linear dielectric tensor 
using Optic utility. 
I use the suggested ngkpt 24X24X24. Such large number of k points will 
use 241049.787 Mbytes of memory in DATASET  4 and 241049.787 Mbytes of memory
in DATASET  5. I try to decrease the ngkpt, but the memory needed is still 
very huge. 

This is beyond our computer, Is there something wrong with the input?

Thank you in advance!

Sincerely,
Bo Liu

the input file is follows

#Prepare the computation of linear and non-linear optic properties

 ndtset 6

#First dataset : SC run with kpoints in the IBZ
   iscf1  3
  nband1  29    
  nstep1 35   
 kptopt1 1
 nbdbuf1 0
 prtden1 1   getden1 0   getwfk1 0    ! Usual file handling data

#Second dataset : NSC run with large number of bands, and points in the IBZ
    iscf2 -2  
   nband2 40  ! This number of bands might be too low for non-linear optics 
and real part of linear optics
   nstep2 35
  kptopt2  1
  getwfk2  1   getden2 1   ! Usual file handling data

#Third dataset : NSC run with large number of bands, and points in the the 
full BZ
    iscf3 -2  
   nband3 40  ! This number of bands might be too low for non-linear optics 
and real part of linear optics 
   nstep3 35
  kptopt3  3
  getwfk3  2   getden3 1   ! Usual file handling data


#Fourth dataset : ddk response function along axis 1
   iscf4 -3
  nband4 40   ! This number of bands might be too low for non-linear optics 
and real part of linear optics
  nstep4  1  nline4  0
 kptopt4  3

   nqpt4  1  qpt4  0.0d0 0.0d0 0.0d0 
  rfdir4  1 0 0
 rfelfd4  2
 getwfk4  3

#Fifth dataset : ddk response function along axis 2
   iscf5 -3
  nband5 40  ! This number of bands might be too low for non-linear optics 
and real part of linear optics
  nstep5  1  nline5  0
 kptopt5  3

   nqpt5  1  qpt5  0.0d0 0.0d0 0.0d0
  rfdir5  0 1 0
 rfelfd5  2
 getwfk5  3

 Sixth dataset : ddk response function along axis 3
   iscf6 -3
  nband6 40   ! This number of bands might be too low for non-linear optics 
and real part of linear optics
  nstep6  1  nline6  0
 kptopt6  3

   nqpt6  1  qpt6  0.0d0 0.0d0 0.0d0
  rfdir6  0 0 1
 rfelfd6  2
 getwfk6  3


#Data common to all datasets

 nshiftk 1
 shiftk 0.5 0.5 0.5
 ngkpt  24 24 24         
acell 7.6024848984E+00  7.6024848984E+00  1.3386132583E+01      
rprim 1.0  0.0  0.0  
      0.0  1.0  0.0  
      0.0  0.0  1.0  

ntypat 3         
znucl 9 17 82                                         
natom 6          
typat 1 1 2 2 3 3        

xred   -4.1633363423E-17 -4.1633363423E-17  0.0000000000E+00
        5.0000000000E-01  5.0000000000E-01  0.0000000000E+00
       -4.1633363423E-17  5.0000000000E-01  6.4645327404E-01
        5.0000000000E-01 -4.1633363423E-17  3.5354672596E-01
       -4.1633363423E-17  5.0000000000E-01  2.0881085270E-01
        5.0000000000E-01 -4.1633363423E-17  7.9118914730E-01

 diemac 3.0
 ecut 40.0          
 iscf 3
 ixc 1
 nbdbuf 2
 tnons 72*0.0
 tolwfr  1.e-20