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