Gaussian 03 Online Manual
Last update: 29 September 2006

formchk

formchk converts the data in a Gaussian checkpoint file into a formatted form which is suitable for input into a variety of visualization software.

formchk has the following syntax:

formchk [-c] [-2] chkpt-file formatted-file

where chkpt-file is the name of the binary checkpoint file to be formatted, and formatted-file is the name for the resultant output file. For example, the following command will produce the formatted checkpoint file propell.fchk from the checkpoint file propell.chk:

$ formchk propell.chk propell.fchk 

The conventional extension for formatted checkpoint files is .fchk on Unix systems and other computers supporting variable-length extensions, and .fck on systems which limit extension to three characters like the PC.

Note that formatted checkpoint files can be used as a data exchange format between computer platforms. Use formchk on the originating computer and unfchk on the target computer to create a binary checkpoint file. The -2 option allows logical arrays and molecular mechanics parameter data. It should always be included when moving files between different types of computers.

The command formchk -c causes the molecular mechanics atom types to appear in the formatted checkpoint file as strings rather than integers.