From VASP Wiki

The ELFCAR file is created when the LELF=.TRUE. in the INCAR file is set and contains the electron localization function denoted by in Ref. [1].

The same file format is used as for the CHGCAR file. That is, lattice vectors, atomic coordinates and number of cartesian sampling points are written, followed by with being the fastest and the slowest index.

For ISPIN=2, is written first followed by .

It is recommended to avoid wrap around errors, when evaluating the ELFCAR file. This can be done by specifying PREC=High in the INCAR file.

  • N.B. The electronic localization function is not implemented for non-collinear calculations.