Gaussian-N composite thermochemical methods

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EDIT: Oh, wait, it's YOU! I don't need to try to teach you anything about GAMESS. PM me :-)

This is one of my long-term interests with NWChem and other quantum chemistry packages that I am writing a job driver for. I did some preliminary tests last year. It is tricky to reproduce the Gn methods exactly in packages other than Gaussian because there is an implicit dependency on Gaussian's orbital freezing conventions for post-HF calculations. I suspect that mean unsigned error across the full test set will not be significantly different using non-Gaussian packages, but I couldn't get the exact same numbers as published when I tried assembling a composite calculation by hand for hydrogen sulfide.

It would be best if you could get the special basis sets submitted to the EMSL Basis Set Exchange. I already have a Python API to get basis sets out of the BSE, store them in a SQLite database, and offer programmable access to them in NWChem, GAMESS-US, and Gaussian94 formats.

After a long period of idling I have returned to the project, but I am working first on automating the individual steps I will need to perform composite calculations. Once that infrastructure is in place I can try whole test sets much faster, and hopefully identify sources/significance of deviations from published results.

I don't have access to Gaussian. I have been calibrating my work from the original publications, the occasional Gaussian log file that you can find on the web, and the composite thermochemical methods implemented in GAMESS-US and Psi4. The GAMESS implementations are quirky. You should search the GAMESS user group archives before diving in with them.

Psi4 has only G2MP2: http://sirius.chem.vt.edu/psi4manual/master/_modules/gaussian_n.html

It's a bit quirky also. It doesn't seem to work beyond first-row elements, and its output is different both because of orbital freezing conventions and because of other speed-for-accuracy tradeoffs used in Psi4 by default (e.g. density fitting for SCF). I have not tried Psi4's implementation across all the test set molecules where it can complete jobs. I should, though, to see how it compares with the published version.

Since I don't use HPC facilities any more and I want to keep my options open, I am writing my code to parse log files instead of use the RTDB, and run separate calculations for different phases of the composite approach. The RTDB approach is cleaner if you stick with NWChem, and of course it is advantageous to be able to submit a single job containing all the phases if you go through a job queue.

Both my basis set data API and the work-in-progress job driver code are on github. I don't want to self-promote here, so send me a PM if you are interested in the code.
Edited On 11:28:53 AM PDT - Sat, May 9th 2015 by Mernst


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