The feff program consists of a set of program modules driven by a single input file ‘feff.inp’ . The user can either supply this file herself; or she can set all input options through the feff GUI, which then creates a ‘feff.inp’ and launches feff without the need for manual text editing or command line activity.

This section describes the input in ‘feff.inp’ or the GUI, and the commands that control feff. It may be helpful to look at the sample input files in Section 3 while reading this section. The current chapter is meant as a reference, while Section 3 makes for friendlier, tutorial-style reading.

The input file ‘feff.inp’ is a loosely formatted, line-oriented text file. Each type of input read by the program is on a line which starts with a CARD, which is a keyword possibly followed by alpha-numeric data. The sequence of keyword cards is arbitrary. If any card or optional data is omitted, default values are used; an exception is the POTENTIALS card, which is always required. Either the ATOMS card or the OVERLAP card is also required for feff to run.

Alpha-numeric values are listed in free format, separated by blanks. Tab characters are not allowed and may cause confusing error messages. Any characters appearing after the card and its required or optional data on a given line are ignored by feff and can be used as end-of-line comments. Empty lines are ignored. Any line beginning with an asterisk (*) is regarded as a comment and is also ignored.

Users working from the GUI do not need to worry about formatting, and can get more information about any CARD by simply hovering the mouse over it.

All distances are in angstroms (Å) and energies are in electron-volts (eV).

An auxiliary perl program (atoms), developed by Bruce Ravel, can generate the ‘feff.inp’ file for crystals from crystallographic input parameters. A perl-based graphical user interface to atoms is available at http://cars9.uchicago.edu/∼ravel/software/aboutatoms.html.

Additionally, feff9 can now also treat crystals specified by their unit cell.

Next Section: Complete list of FEFF9 control cards

Back to FEFF Document Contents

developer's resources