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# 2.5.1 Overview

(February 4, 2022)

In order for individual users to run Q-Chem, User file access permissions must be set correctly so that the user can read, write and execute the necessary Q-Chem files. It may be advantageous to create a qchem user group on your machine and recursively change the group ownership of the Q-Chem directory to qchem group.

The Q-Chem run-time environment need to be initiated prior to running any Q-Chem calculations, which is done by sourcing the environment setup script qcenv.sh (for bash) or qcenv.csh (for csh and tcsh) placed in your Q-Chem top directory after a successful installation. It might be more convenient for user to include the Q-Chem environment setup in their shell startup script, e.g., .cshrc or .tcshrc for csh or tcsh, respectively, or .bashrc for bash.

If using the csh or tcsh shell, add the following lines to the .cshrc file in the user’s home directory:

#
setenv  QC         qchem_root_directory_name
setenv  QCSCRATCH  scratch_directory_name
source  $QC/qcenv.csh #  If using the Bourne-again shell (bash), add the following lines to the .bashrc file in the user’s home directory: # export QC=qchem_root_directory_name export QCSCRATCH=scratch_directory_name .$QC/qcenv.sh
#