## ENCUT convergence check increasing rather than decreasing

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rajeshraju
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Posts: 2
Joined: Fri Jan 05, 2018 3:54 pm

### ENCUT convergence check increasing rather than decreasing

Hi,

I am woking on N-doped graphene (49 C and 1 N) and did convergence check to see the optimal (or the best) K and Encut values to be chosen for the minimization. I got the following numbers which show some ups and downs in the total energy written in the OUTCAR (energy sigma->0). Any help to figure it out? I presume, higher K-point and EnCut should provide better values.

400 -459.86236853 -459.8575553 -459.8566265
450 -459.52324679 -459.5181853 -459.5175918
500 -459.41923826 -459.4143076 -459.4138069
550 -459.43005966 -459.4251268 -459.4245913
600 -459.53038956 -459.5255936 -459.5249424

I read in the forum something we should substract kinetic energy erorr from the total energ before checking the values? I got the following the values for Kinetic Energy Error. That means I have to multiply 0.0057 x 49 and 0.0103 one time for each other. This was not clear in the forum answer.
kinetic energy error for atom= 0.0057 (will be added to EATOM!!)
kinetic energy error for atom= 0.0103 (will be added to EATOM!!)

the INCAR for Single point energy on the optimized geometry is shown below to check whether there is any error or not

# Basic setup:
SYSTEM = N-doped Graphene
ISPIN = 2
NCORE=24
KPAR=5
LSORBIT = .FALSE.
# not using Hubbard U

# Accuracy controls:
# PREC = High
ENCUT = 600

# Electronic loop controls:
ALGO = Fast # Fast (Davidson + RMM-DIIS)
EDIFF = 1E-7
NELMIN=15
NELM=60
#TIME = 0.400000
ISMEAR = 2 # 2nd order Methfessel-Paxton method
SIGMA = 0.2 # eV
# NBANDS = 144

# Relaxation control:
IBRION = -1
NSW = 0
POTIM = 0.2
ISIF = 2 # Ions Cell Volume
EDIFFG = 1E-5

# Properties:
LCHARG = .TRUE.
LWAVE = .TRUE.
# LVTOT = .FALSE. #Default False
# LVHAR = .FALSE.

Thanks
Rajesh

alex
Sr. Member
Posts: 490
Joined: Tue Nov 16, 2004 2:21 pm