INCAR

The INCAR file is the central input file of VASP. It determines what to do and how to do it. There is a relatively large number of parameters that may be set using tags in the INCAR file. We chose reasonable default values and recommend using them when unsure about the meaning of a parameter.

Important: Be very careful about the INCAR file, it is the main source of errors and false results!

The INCAR file is a tagged format free-ASCII file: Each statement consists of the name of a tag, the equals sign =, and the values assigned to the tag. Typically each line contains a single statement, but it is possible to combine multiple statements on a single line separating them by a semicolon ;.

Split long lines with a backslash \ for better readability. Avoid blanks after the backslash because some versions of VASP cannot parse those. Alternatively, enclose all the values in quotes " to ignore all line breaks between the quotes.

Any text after a number sign # or exclamation mark ! is ignored. Use this to add comments to the INCAR file. Reading the file will also ignore all text that does not fit the statement format (tag = values) so often a comment prefix is not necessary. In this case, do not use any syntax relevant character (=;") because this may break the parsing of the INCAR file.

Avoid lines with tabs to avoid issues we encountered for some compilers.

Tip: VASP reports its interpretation of the data in the INCAR file back to the OUTCAR file. Please verify that this agrees with the intended setup.

A typical (relative complex) INCAR can be found below:

SYSTEM = Rhodium surface calculation

# start parameters for this Run (automatic defaults are finem, hence not often required)
  ISTART =      0    #  job   : 0-new  1- orbitals from WAVECAR
  ICHARG =      2    #  charge: 1-file 2-atom 10-const

# electronic optimization
  ENCUT  = 300.00 eV # defaults from POTCAR, but wise to include
  ALGO  =     Normal # alorithm for electron optimization, can be also FAST or ALL
  NELM   =     60    # of ELM steps, sometimes default is too small 
  EDIFF  =   1E-06   # stopping-criterion for ELM
# broadening and DOS related values; this works almost always
  SIGMA  =    0.05;  ISMEAR =  0 # broad. in eV, -4-tet -1-fermi 0-gaus

# ionic relaxation
  EDIFFG =  -1E-02   # stopping-criterion for IOM (all forces smaller 1E-2)
  NSW    =       20  # number of steps for IOM
  IBRION = 2         # CG for ions, often 1 (RMM-DISS) is faster
  POTIM  =    .5     # step for ionic-motion (for MD in fs)
# performance optimization
  KPAR   =    4      # make 4 groups, each group working on one set of k-points 
  NCORE  =    4      # one orbital handled by 4 cores 
  LREAL  =    A      # real space projection; slightly less accurate but faster 

• A comprehensive list of all INCAR tags and related articles.

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