The ABINIT Users Mailing List ( CLOSED )

[Manuel Pérez Jigato <Manuel.PerezJigato@fys.kuleuven.be>]

Dear all,

when running GW for a cubic oxide, i seem to be getting different  
behaviour for ABINIT in the screening/inverse dielectric matrix  
calculation, depending on the
way i set up the input (do it all in one run vs do SCF separately and  
restart for the rest).

Let me get more explicit.

case 1
If i follow the silicon example that appears in the GW1 tutorial, and  
do the gamma point GW correction in one run (exactly as in input file  
"tgw1_9.in"), ie,
- SCF calculation
- KSS file generation
- screening matrix calculation
- self-energy matrix elements and GW correction to the highest  
occupied and lowest unoccupied bands

in this case, the screening part seems to be doing what it should  
(according to the silicon test case "tgw1_9") and it finds the whole  
lot of q-points in the part printed as

 number of q-points found       85
 find q-points q = k - k1 and translate in first BZ
 q-points [reduced coordinates]
-----then the list of q points follow.....


case 2
If instead, i do separately the SCF calculation from the rest  
(according to the tutorial, you could save time doing SCF with full  
symmetry, and the next calculation KSS-screening-selfenergy/GW using  
symmorphi 0) in this case, the
screening/inverse dielectric matrix part seems to do something  
different to the above, ie, it computes chi0 and epsilon-1 only for  
the gamma point:

 number of q-points found        1
 find q-points q = k - k1 and translate in first BZ
 q-points [reduced coordinates]
    0.000010    0.000020    0.000030

Let me enclose the input files corresponding to both cases, ans well  
as the output for the "wrong" case (second case).

Is there any good reason for the difference in behaviour? I guess when  
you compute big systems, it is advisable to do the SCF part separately  
with the full symmetry. In the convergence tests in GW1 for silicon,  
it is convenient
to do restarts as well.

thanks

Manuel Perez Jigato
KU Leuven





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