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VASP INCAR

INCAR VASP Wiki

This file is the main input file to tell VASP what to calculate and what settings you want VASP to use. There are a lot of different tags you can add and many tags affect multiple different settings.

Follow the link for a list of all INCAR tags: Link

Important INCAR Tags

IBRION

Tells VASP what method to do.

  • IBRION = 0 is for Molecular Dynamics.
  • IBRION = 2 is for Conjugate Gradient Geometry Optimization.
  • IBRION = -1 with NSW = 0 is a single point calculation.

ISIF

Tells VASP what constraints you want the calculation to have.

  • ISIF = 2 is to optimize the atom positions with a fixed unit cell shape and volume.
  • ISIF = 3 is to optimize the unit cell shape, volume and atom positions.
  • ISIF = 4 is to optimize unit cell shape and atom positions with a fixed unit cell volume.
  • ISIF = 7 is to optimize unit cell volume with a fixed shape and atom positions.

PREC

Tells VASP how precise you want the calculation. It provides cut off energies, convergence criteria etc. The two main options are PREC = Normal or PREC = Accurate

ENCUT

Defines the energy cutoff for the basis set used in the VASP calculation. This value is set by the PREC INCAR tag automatically but the VASP Wiki suggests you should manually set it anyway. The amount of ENCUT could determine if a calculation fully converges and finds a minima structure.

NCORE and NPAR

These tags are for parallelization of VASP. You need to use one or the other tag in the INCAR file.

  • NCORE determines how many cpus work on one orbital.
  • NPAR determines how many orbitals will be ran at one time.

For 1 node jobs on Nocona:

NCORE = should be a low amount of cpus, so if you request 36 cpus, NCORE could be 4.

Don't provide NPAR since you provided NCORE.

Geometry Optimization INCAR

Below is a example INCAR file for Geometry Optimization.

INCAR
SYSTEM = GEO OPT
NSW = 600
LREAL = A
IALGO = 48
ISMEAR = 0
IBRION = 2       #   ionic relax: 0-MD 1-quasi-New 2-CG, 5,6- freq.calc
ISIF = 2         #const. cell and volume, opt.ions
#ISIF = 3         #opt cell shape and volume and ions
#ISIF = 4         # opt cell shape and ions at const. volume
#ISIF = 7         # opt cell volume - fixed shape and ion pos.
NSIM = 1
ISYM=0
#ENCUT=350
#ENCUT=600
#PREC=High
#PREC=Accurate
PREC=Medium
#EDIFF = 1E-5
#EDIFFG = -0.015
#NPAR = 8
NCORE=4
#AMIN=0.02
#dispersion corrections D3
IVDW=12

Note: If a line is commented, VASP will not read it (Just like Bash and Python).

Phonopy Displacement INCAR

Below is an example of the INCAR you would need to use for a phonopy displacement calculation using VASP.

INCAR
SYSTEM = Phonopy
PREC = Accurate
ENCUT = 800 #obtained using ENCUT convergence TEST
IBRION = -1 #static calcs
ISIF = 2 #stress tensor and forces of atomic displacemnts. 1 DOF
EDIFF = 1E-5
ISMEAR = 0
SIGMA = 0.01 # Recommended
NSW = 0
LCHARG = .TRUE.
LWAVE = .TRUE.
NCORE = 4