2 Installation, Customization, and Execution

2.3 Q-Chem Auxiliary files ($QCAUX)

(June 30, 2021)

The $QCAUX environment variable determines the directory where Q-Chem searches for auxiliary files and the machine license. If not set explicitly, it defaults to $QC/qcaux.

The $QCAUX directory contains files required to run Q-Chem calculations, including basis set and ECP specifications, SAD guesses (see Chapter 4), library of standard effective fragments (see Section 11.5), and instructions for the AOInts package for generating two-electron integrals efficiently.