This file contains the lattice vectors and atomic coordinates followed by the total real space charge density on the large FFT-grid (NG(X,Y,Z)F) as derived from the last selfconsistency step in the electronic minimisation loop of the job. From VASP version 2.0 it is possible to avoid, that the CHGCAR is written out by setting
LCHARG = .FALSE.in the INCAR file (see section 7.43). The file is written using the following commands in Fortran
WRITE(IU,FORM) (((C(NX,NY,NZ),NX=1,NGXC),NY=1,NGYZ),NZ=1,NGZC)The x index is the fastest index, and the z index the slowest index. The file can be read format-free, because at least in new versions it is guaranteed that space separates each number.
For dynamic simulation (IBRION=0) the charge density might be predicted for the next step: i.e. it is compatible with CONTCAR and not compatible with the last calculated positions, this way the CHGCAR and the CONTCAR file can be used consistently for a molecular dynamics continuation job. For static calculations and relaxations (IBRION=-1,1,2) the written charge density is the selfconsistent solution of KS-equations for the last step, and might be used e.g. for accurate band-structure calculations (see section 11.3).
Mind: NEVER continue a bandstructure calculation with ICHARG=11 from a dynamic simulation (IBRION=0) (see section 11.3). The charge density written to the file CHGCAR, might be predicted, and is not the self consistent solution for the CONTCAR file. Copy CONTCAR to POSCAR, and make another static (ISTART=1; NSW=0) continuation run with ICHARG=1. For reasons of safety do the same for relaxation runs (IBRION=1,2).