I'm currently working with two quantum software packages: Gaussian 09 and CFour. CFour does a very good job giving explicit control over how you want to invoke frozen core approximations and explains how the default handling is done via the
Gaussian 09 has a documentation page regarding frozen core. All my Gaussian 09 jobs with frozen core use the
FC flag in the route section. It is important to note that frozen core is basis-set dependent, meaning, the criteria for choosing which core(s) to freeze is directly correlated with the implemented basis set.
I've implemented the following basis sets in Gaussian:
What I Need
I need to know if CFour and Gaussian 09 handles the frozen core approximation the same (particularly related to the listed basis sets above). More specifically, if I use the
FC option in Gaussian, will invoking the
FROZEN_CORE=ON option be sufficient for comparable data or will I need to use the
DROPMO command and explicitly tell CFour which core(s) to freeze? If the latter, how do I determine which orbitals to freeze as to match that of Gaussian 09?
The answer may be right in front of me on the documentation pages but it seems rather ambiguous. Of course some benchmark computations could be done to analyze this but I'd rather ask before embarking on such an endeavor that eats precious CPU clock cycles.
This question is strictly about program handling and job control.