VASP.4.X is a Fortran 90 program. This allows for dynamic memory allocation and a single executable which can be used for any type of calculation.
Generally the source code and the pseudo potentials should reside in the following directories:
VASP/src/vasp.4.lib VASP/src/vasp.4.X VASP/pot/.. VASP/pot_GGA/.. VASP/potpaw/.. VASP/potpaw_GGA/..The directory vasp.4.lib contains source code which rarely changes and this directory usually does not require re-installation upon updates. However, significant changes in vasp.4.lib might be required, when adopting the code to new platforms. The directory vasp.4.X contains the main Fortran 90 code. The directories pot/ pot_GGA/ (and possibly potpaw/ potpaw_GGA/) hold the (ultrasoft) pseudopotentials and the projector augmented wave potentials respectively. LDA versions are supplied in the directories pot and potpaw, whereas GGA versions (Perdew, Wang 1991) are distributed in the directories pot_GGA and potpaw_GGA. The source files and the pseudopotentials are available on a file server (see section 3.2).
Most calculations will be done in a work directory, and before starting a calculation, several files must be created in this directory. The most important input files are:
INCAR POTCAR POSCAR KPOINTS