The makeparam utility generates automatically the param.inc file (an include file that is required in the f77 version). Mind: the utility makeparam is no longer required in VASP.4.X, but to learn something about the default setting for NGX, NGXF etc. read this section. In vasp.4.4 the makeparam can be used to estimate the memory requirements of the code.
The program is started by typing
> makeparamand it prompts an appropriated param.inc file to the screen. Before running the makeparam utility all other input files (INCAR, POSCAR, POTCAR and KPOINTS) must exist in the current work directory.
The values for NGX,Y,Z are controlled by the PREC-tag in the INCAR file. Possible values for PREC are
For PREC=High wrap around errors are avoided (see section 9.2). For PREC= Low or Medium the 3/4 rule is used (see section 10.4), i.e. NGX,Y,Z is set to 3/4 of the value, which avoids wrap around errors. (The main difference between PREC=Low and PREC=Med is the determination of the default energy cutoff ENCUT 7.7). The values for NGXG, NGYF and NGZF are determined from the necessary cut-off for the augmentation charge ENAUG (see section 7.6).
To summarize: Three flags in the INCAR file control the makeparam utility:
Determines the first FFT-grid, which is used to represent the charge density potentials and wavefunctions. If ENCUT does not exist in the INCAR file it will be determined from the POTCAR file. For PREC=Low, ENCUT will be set to the maximal ENMIN value found on the POTCAR files, for PREC=Medium or High ENCUT will be set to maximal ENCUT value on the POTCAR file (see 5.4).
Determines the second fine grid, which is used to represent the augmentation charges. If ENAUG does not exist in the INCAR default will be be determined from the POTCAR file.
This tag determines whether wrap around errors are allowed or not: for PREC=High wrap around errors are avoided (see section 9.2); for PREC=Med or PREC=Low, wrap around is allowed (3/4 rule).