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[Dev Sharma <champbond1983@gmail.com>]

hi 2 all,

I tried to do Gw calculations for my system YVO4. I have some doubts. I followed the examples tgw1_1 but not getting the results. Neither the dielectric constant , dielectric constant with local fields is printed nor the E, E GW gap and Delta GW. I have not used very high convergance as for starting the work  i want to check with low convergance(then will increase the convergence). 
My input file is listed below . Please help.

1)  nband1      100         # these 100 are occupied and empty. How can we know that out of 100 how may are occupied and how many unoccupied ??

2)  what is usual value given to nband2 and nband3 ??

3) bdgw3       41  42     # here i want to ask, how we will find these number. Since i want the band gap b/w the top of valance band and bottom of conduction band. is this 41 and 42 represent the top of VB and bottom of CB ??? or we can do correction b/w any bands ???

ndtset      3

 nbandkss1   -1         #

nband1      100         #

#istwfk1     10*1     # this point is not clears

 

# Calculation of the screening (epsilon^-1 matrix)

optdriver2  3        # Screening calculation

getkss2     -1       # Obtain KSS file from previous dataset

nband2      115       # Bands to be used in the screening calculation

ecutwfn2    4.1      # Cut-off energy of the planewave set to represent the wavefunctions

ecuteps2    5.6      # Cut-off energy of the planewave set to represent the dielectric matrix

ppmfrq2    16.7 eV  # Imaginary frequency where to calculate the screening

 # Calculation of the Self-Energy matrix elements (GW corrections)

optdriver3  4        # Self-Energy calculation

getkss3     -2       # Obtain KSS file from dataset 1

getscr3     -1       # Obtain SCR file from previous dataset

nband3      130       # Bands to be used in the Self-Energy calculation

ecutwfn3     2.0     # Planewaves to be used to represent the wavefunctions, use 5

ecutsigx3     2.0     # Dimension of the G sum in Sigma_x, use 6

                     # (the dimension in Sigma_c is controlled by npweps)

nkptgw3      1                # number of k-point where to calculate the GW correction

kptgw3                       # k-points

  0.000    0.000    0.000

bdgw3       41  42             #

#Definition of the unit cell (YVO4 is tetragonal)

acell 13.451637476  13.451637476  11.885054518  

angdeg  90 90 90

 chkprim 0

#Definition of the atom types

ntypat 3          # There r 3 type of atom

znucl 39 23 8          # The keyword "znucl" refers to the atomic number of the

#Definition of the atoms

natom 24         

typat 1 1 1 1 2 2 2 2  3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3       

 

 xred              

    0.0000  0.0000  0.0000

   /

  /

    0.3030  0.0000  0.0700

 # Definition of the k-point grid

kptopt  1            # Option for the automatic generation of k points,

nkpt    6

ngkpt   2 2 2 # use 4 4 4 

nshiftk 1

shiftk 

        0.0 0.0 0.0

istwfk  24*1          # This is mandatory in all the GW steps.

 

# Use only symmorphic operations

symmorphi 1

 

# Definition of the planewave basis set (at convergence 16 Rydberg 8 Hartree)

ecut 2.0          #  use 10

 

# Definition of the SCF procedure

nstep   100        # Maximal number of SCF cycles

toldfe  1.0d-1    #  10-7

diemac  12.0      # Although this is not mandatory, it is worth to

               

# This line added when defaults were changed (v5.3) to keep the previous, old behaviour

  iscf 5