The ABINIT Users Mailing List ( CLOSED )

[ธนูสิทธิ์ บุรินทร์ประโคน <thanusit@kku.ac.th>]

Dear Yu Zhou and All

The problem arises in screening calculation when k-q-G0 is not a recprocal vector. This seems to happen when we use an irregular k-point grid, even with the standard method of specifying the k-grid.

Could the Abinit team have any suggestion  to get round this problem?  What is the criterior to justify that k-q-G0 is not a recprocal vectors?  Does it have anything to do with the precision of the kpt values we input?

Regading Zhou's GW calculation, please make sure the k-point assigned for kptgw is one of those contained in the list used in th KSS file calculation. Otherwise you will get another error in the GW calculation.

 

Kind Regards,

Thanusit Burinprakhon

 

On June 19, 2008 12:16:57 AM ICT, zhouy6@rpi.edu wrote:

> Hi dear all,
>
> I'm trying to calculate the GW correction at the K-point (0, 0.4157, 0.4157),
> and I tried to use "standard" procedure by using ngkpt and nshiftk and shiftk
> in the second DATASET.
>
> but I kept seeing this error, seems that the "standard" method only works for
> those grid points, not for an irregular k-point.
>
> cchi0 : ERROR -
> kp=k-q-G0 not found
> ik = 1 k = -0.125000 -0.084300 0.040700
> k-q = -0.375000 -0.252900 0.122100
>
> leave_new : decision taken to exit ...
>
>
> Could someone help me find out what the problem is?
>
> Thanks
>
> Yu Zhou
>
> ============
> here is my input file:
>
> ndtset 4
>
> kptopt 1
> ngkpt 4 4 4
>
> # Dataset1: usual self-consistent ground-state calculation
> nshiftk1 4
> shiftk1 0.5 0.5 0.5
> 0.5 0.0 0.0
> 0.0 0.5 0.0
> 0.0 0.0 0.5
> prtden1 1
>
>
> # Dataset2: calculation of kss file
> nshiftk2 4 
> shiftk2 0.0 1.6628 1.6628
> 0.0 2.1628 2.1628
> 0.5 1.6628 2.1628
> 0.5 2.1628 1.6628
> istwfk2 60*1
> iscf2 -2
> getden2 -1
> nband2 9
> nbandkss2 -1
>
> # Dataset3: Calculation of the screening (epsilon^-1 matrix)
> optdriver3 3
> getkss3 -1
> nband3 25
> ecutwfn3 3.6
> ecuteps3 6.0
> ppmfrq3 16.7 eV
>
> # Dataset4: Calculation of the Self-Energy matrix elements (GW corrections)
> optdriver4 4
> getkss4 -2
> getscr4 -1
> nband4 100
> ecutwfn4 5.0
> ecutsigx4 6.0
>
> nkptgw4 1
> kptgw4
> 0.000 0.4157 0.4157
> bdgw4 4 5
>
>
> # Definition of the unit cell: fcc
> acell 3*10.217 # This is equivalent to 10.217 10.217 10.217
> rprim 0.0 0.5 0.5 # FCC primitive vectors (to be scaled by acell)
> 0.5 0.0 0.5 
> 0.5 0.5 0.0
>
> # Definition of the atom types
> ntypat 1 # There is only one type of atom
> znucl 14 # The keyword "znucl" refers to the atomic number of the 
> # possible type(s) of atom. The pseudopotential(s) 
> # mentioned in the "files" file must correspond
> # to the type(s) of atom. Here, the only type is Silicon.
>
> # Definition of the atoms
> natom 2 # There are two atoms
> typat 1 1 # They both are of type 1, that is, Silicon.
> xred # Reduced coordinate of atoms
> 0.0 0.0 0.0
> 0.25 0.25 0.25
>
> # Definition of the planewave basis set (at convergence 16 Rydberg 8 Hartree)
> ecut 8.0 # Maximal kinetic energy cut-off, in Hartree
>
> # Use only symmorphic operations
> symmorphi 0
>
> # Definition of the SCF procedure
> nstep 10 # Maximal number of SCF cycles
> diemac 12.0 # Although this is not mandatory, it is worth to
> # precondition the SCF cycle. The model dielectric
> # function used as the standard preconditioner
> # is described in the "dielng" input variable section.
> # Here, we follow the prescription for bulk silicon.
> tolwfr 1.0d-10 
>
> # This line added when defaults were changed (v5.3) to keep the previous, old
> behaviour
> iscf 5