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rishikanta_m
- Jr. Member
- Posts: 72
- Joined: Wed Jun 15, 2022 5:52 am
#1
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by rishikanta_m » Thu Jul 27, 2023 4:55 am
Hi,
I am running a PBE calculation with zero kpoints for a slab. The INCAR file is such:
Code: Select all
# Wave calculation
ISTART = 0
ICHARG = 2
# general
ENCUT = 500
LWAVE = .TRUE.
# SCF specific setting
IBRION = -1
NSW = 0
ISMEAR = 0
SIGMA = 0.02
EDIFF = 1E-5
NELM = 300
# LORBIT = 11
LSORBIT=.TRUE.
SAXIS= 0 0 1
ISYM=0
# For large systems
LREAL=Auto
ALGO=FAST
LPLANE =.TRUE.
However, in the OSZICAR, the EDIFF reaches 1E-05 but still has not converged and still running. What can be the issues? The oszicar file is attached.
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pedro_melo
- Global Moderator
- Posts: 127
- Joined: Thu Nov 03, 2022 1:03 pm
#2
Post
by pedro_melo » Thu Jul 27, 2023 8:02 am
Dear rishikanta_m,
When you wrote that you are running a calculation with zero k-points, what exactly did you mean? For a very large system or a molecule, all calculation will have one k-point, Gamma.
Another point: the total energy of the system is an extensive quantity, so it will increase with the number of atoms. Depending on that number it might be unreasonable to ask any code to converge the total energy to the same precision as a system with only 2 or 3 atoms per unit cell.
Finally, results with ALGO=FAST are often used for quick calculations, and can lead to inaccurate results. I suggest that you change it to NORMAL and see if the convergence improves.
Kind regards,
Pedro Melo