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Running Parsec

Basic input

• parsec.in : input file with user-provided parameters.

• *_POTRE.DAT : pseudopotential files, in format consistent with Prof. J.L. Martins' pseudopotential generator. The distributors of Parsec have a version of Prof. Martins' code with minor but important modifications, so that files in the proper format are created. For the moment, only norm-conserving pseudopotentials are implemented. For back-compatibility, files in "old format" are also accepted, see below Old_Pseudopotential_Format flag. Pseudopotential files used in Parsec are compatible with the "Siesta" DFT program, but the opposite is not true: pseudo-wavefunctions are appended to *_POTRE.DAT files, but the same does not necessarily happen to formatted pseudopotential files used in Siesta.

The parsec.in file

The user-provided input uses the electronic structure data format (ESDF), implemented as a module written by Chris J. Pickard. Comments can be added on any line, and are preceded by any of the symbols "# ; !". Keywords and blockwords are case insensitive. Characters ". : =" and multiple spaces are ignored. Most parameters have default values. All parameters with true/false value have default value false. Parameter values can be written anywhere in the file, with the exception that information pertinent to the same chemical element should be given in consecutive lines (sometimes, data from different elements can be mixed, but this should be avoided for the sake of clarity). Keywords are always followed by their corresponding value on the same line. Input values with intrinsic physical unit can be given in different units, with name following the value. Default unit is used if none is specified. For example, the line grid_spacing 0.5 ang sets a grid spacing of 0.5 angstroms. Blocks have the syntax:

begin Blockword
.
.
.
end Blockword

WARNING: parsec does not watch out for misprints in parsec.in. Lines with unrecognized keywords or blockwords are usually ignored.

Basic output

• parsec.out : unified output file.

• out.* : standard output. It contains some warnings and error messages.

• wfn.dat : contains eigenvalues, density function, effective potential, wave-functions and other output data, in binary (unformatted) form. See Olddat_Style.