I want to add GW approximation in band structure calculations. For relaxation step, i have just used the POTCAR file of GW corrections, other files as usual. Then for self-consistent i have to make changes in INCAR? i have done this by making changes in INCAR by LOPTICS=.TRUE., ISMEAR=0, SIGMA=0.05, NBANDS=40, after these in OSZICAR file dE is not equal to zero. So, i want to know, where i am doing the mistake?
As you know "dE" is the change of the free energy between two steps, and d eps the change of the band-structure energy. The ncg, rms and rms(c) are important for check the data . your order is as: LOPTICS=.TRUE., ISMEAR=0, SIGMA=0.05, NBANDS=40
small sigma is required to avoid partial occupanciy
it is important that the a significant number of empty bands is required for GW calculations, so that it might be better to perform the calculations in two steps: first a standard grounstate calculation with few unoccupied orbitals only,
First:
System = ..... groundstate occupied orbitals
ISMEAR = 0 ; SIGMA = 0.05
EDIFF = 1E-8 ! required tight tolerance for groundstate orbitals
Second a calculation of a large number of unoccupied orbitals
System = .... unoccupied orbitals
ALGO = Exact
NELM = 1
NBANDS = 40
ISMEAR = 0 ; SIGMA = 0.05 ! small sigma is required to avoid partial occupancies
LOPTICS = .TRUE.
In addition the flag LOPTICS=.TRUE. is required in order to write the file WAVEDER
Then your system will be work and the dE is gonna be near zero
Don't hesitate to contact me for any further discussion or question
Thanks to all for your kind responses. But, after second step i have not get dE=0. These are my INCAR files for first and second step respectively.
# Basic setup:
SYSTEM = groundstate occupied orbitals
ISTART = 0
ICHARGE = 2
ISMEAR = 0
SIGMA=0.05
EDIFF = 0.00000001
PREC = HIGH
LWAVE = .FALSE.
LCHARGE = .TRUE.
LVTOT = .FALSE.
ENCUT = 450
IBRION = -1
LREAL = Auto
NSW = 0
VOSKOWN = 1
-
for 2nd step...
# Basic setup:
SYSTEM = unoccupied orbitals
ISTART = 0
ICHARGE = 2
ALGO=Exact
NELM=1
NBANDS=40
LOPTICS=.TRUE.
ISMEAR = 0
SIGMA=0.05
EDIFF = 0.00000001
PREC = HIGH
LWAVE = .FALSE.
LCHARGE = .TRUE.
LVTOT = .FALSE.
ENCUT = 450
IBRION = -1
LREAL = Auto
NSW = 0
VOSKOWN = 1
-
Please tell me where i am doing the mistake.
Sir, i want to ask one more thing that while including GW approximations which POTCAR file should we use? i am using PBE GW potentials from vasp database. Am i correct or not?
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