Computational Chemistry at NCSA

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Frequently Asked Questions

1. I cannot find my Gaussian output files.
   If Gaussian jobs are incomplete and a stale link is found for your output file in your home directory, please remove it (using the rm command) and retrieve the file saved in the NCSA mass storage system (using the msscmd get command). Similarly, checkpoint files can also be retrieved from the mass storage. This may be automated soon.

   How can I access Gaussian utilities on the NCSA HPC systems?

   To avail Gaussian utilities on NCSA systems, please add

   +gaussian 
   

   to the top of your $HOME/.soft file, and run the resoft command or log off and log back on. This will permanently add the Gaussian utilities to your environment.

   Alternatively, to access it in your current session only, issue the command

   soft add +gaussian
   

   on the command line.

   I am running an MP2 frequency calculation using Gaussian. I requested 8 processors but the job is running with 2 or 3 processors. Why is my job running with a smaller number of processors than I requested?

   If you see messages like number of processors reduced in the output, more than likely the reason is insufficient memory. You need to estimate memory better. The memory for multiprocessor (n) job is n/2+1 times memory for single processor which can be estimated using the formula in the manual (see Estimating Calculation Memory Requirements in the Gaussian manual)

   How can I get access to CHARMM and VASP?

   Support for CHARMM (Prof. Martin Karplus) and VASP (Prof. Jurgen Hafner) at NCSA is limited to helping compile at present.

   Please contact chemist@ncsa.uiuc.edu with any questions.