PSCTR

The PSCTR file controls the pseudopotential generation program (rhfsps) and the calculation of the US pseudopotentials (fourpot3). A simple PSCTR file might have the following contents:

TITEL  = Pd: NC=2.0 US=2.7, real-space 200eV, opt
   LULTRA =        T    use ultrasoft PP ?
   RWIGS  =    2.600    Wigner-Seitz radius

   ICORE  =        0    local potential
   RMAX   =    3.000    core radius for proj-oper
   QCUT   =    4.000; QGAM   =    8.000    optimization parameters

   Description
     l     E      TYP  RCUT    TYP  RCUT
     0   .000     15  2.100    15  2.100
     2   .000      7  2.000    23  2.700
     2  -.600      7  2.000    23  2.700
     1   .000      7  2.700     7  2.700

Different Pseudopotentials can be generated:

• BHS: G.B. Bachelet, M. Schlüter and C. Chiang PP [38]
• VAN: Vanderbilt-pseudopotential [39]
• XNC: E.L. Shirley, D.C. Allan, R.M. Martin J.D. Joannopoulos, [40]
• TM : Troullier and Martins [42]
• RRKJ: A.M. Rappe, K.M. Rabe, E. Kaxiras and J.D. Joannopoulos [43]

  and variants [18]

For a short summary with a description of the parameters of each scheme see [12] (thesis, G. Kresse in German), if you do not understand German we refer to the original articles. We recommend to use the RRKJ scheme only, if you are using only this scheme read both references for the RRKJ scheme given above.

The PSCTR file is a tagged format free-ASCII file (similar to INCAR, section 6): Each line consists of a tag (i.e. a string) the equation sign '=' and a number of values. It is possible to give several parameter-value pairs ( tag = values ) on a single line, if each of these pairs are separated by a semicolon ';'. If a line ends with a backlash the next line is a continuation line. Comments are normally preceded by the number sign '#', but in most cases comments can be append to a parameter-value pair without the '#'. In this case semicolons should be avoided within the comment.

A lot of information is passed via the POTCAR file from the pseudopotential generation package to VASP/VAMP. Among the most important information is the default energy cutoff (see section 11.3.