Using Gaussian Checkpoint FilesDavid Young
Cytoclonal Pharmaceutics Inc.
When a calculation is started using information from a checkpoint file, the calculation results will be placed in the exact same checkpoint file, overwriting the original checkpoint file. Thus it is always a good idea to make a backup copy of the checkpoint file. Note that it is possible for a checkpoint file to become corrupted (i.e. if a calculation dies while writing to the checkpoint file).
Gaussian will use a checkpoint file if the command
%Chk=file_nameappears before the route card in the input file. If the specified file does not exist, it will be created. If the specified file does exist, information to be used in the present calculation can be read from it.
Commands for reading from the checkpoint fileA calculation can be started using information from the checkpoint file by including one of the following commands in the route card.
Checkpoint file UtilitiesThe c8694 utility can be used to convert a checkpoint file from an old format (Gaussian 86 through Gaussian 92/DFT) to the Gaussian 94 format. It is given a single argument, which is the name of the checkpoint file. The file is overwritten by a new file with the same name.
chkchk is a utility provided with the Gaussian distribution. It extracts the title and route sections from a checkpoint file. The command usage is
chkchk file_namewhere file_name.chk is the name of a checkpoint file in the current directory.
chkmove is another utility provided with Gaussian. It is used to move checkpoint files between machines of different architecture. Using ftp in binary mode to transfer a checkpoint file between machines of different architecture will not result in having a readable file on the new machine. In order to transfer a file between machines of dissimilar architecture, the steps that must be followed are
The formchk utility can be used to generate a formated (ASCII) version of the checkpoint file. formchk is used with the command line
formchk file_name.chk file_name.fchkwhere the first file name is the binary checkpoint file and the second is the name of the file to create. Using the formchk utility after the completion of a job does not allow as much flexibility of output format as is available by using the FormCheck keyword when the job is run.
The freqchk utility can be used to extract vibrational frequency and thermochemistry information from a checkpoint file. It can also be used to create files which can be read by HyperChem and used to animate the vibrational modes.
Creating an ASCII checkpoint fileThe FormCheck keyword can be used to request that an ASCII version of the checkpoint file be created. It is always given the name Test.FChk and placed in the current directory. This file is not readable by the Gaussian program. FChk and FCheck are synonyms for FormCheck. The FormCheck command has a number of options which are explained fully in the "Gaussian User's Guide".
Further InformationAn introductory description of how to use Gaussian is in
J. B. Foresman, A. Frisch "Exploring Chemistry with Electronic Structure Methods: A Guide to Using Gaussian" Gaussian (1993)
Commands are described in detail in
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