Extension of Gaussian-2 (G2) theory to molecules containing third-row atoms K and Ca

Autor:	Leo Radom, Larry A. Curtiss, Jean-Philippe Blaudeau, Mark P. McGrath
Rok vydání:	1997
Předmět:	Chemistry Gaussian Hartree–Fock method General Physics and Astronomy Thermodynamics Electronic structure Dissociation (chemistry) symbols.namesake Ab initio quantum chemistry methods Test set symbols Physical and Theoretical Chemistry Atomic physics Scaling Gaussian process
Zdroj:	The Journal of Chemical Physics. 107:5016-5021
ISSN:	1089-7690 0021-9606
Popis:	Gaussian-3 (G3) theory is extended to molecules containing the third-row nontransition elements K, Ca, Ga–Kr. Basis sets compatible with those used in G3 theory for molecules containing first- and second-row atoms have been derived. The G3 average absolute deviation from experiment for a set of 47 test reactions containing these elements is 0.94 kcal/mol. This is a substantial improvement over Gaussian-2 theory, which has an average absolute deviation of 1.43 kcal/mol for the same set. Variations of G3 theory are also presented that are based on reduced orders of perturbation theory. These variations also show similar improvement over the corresponding G2 methods. The use of scaling parameters in G3 theory for the third row was investigated and found to perform nearly as well as use of the higher level correction. In addition, these methods are evaluated on a set of molecules containing K and Ca for which the experimental data are not accurate enough for them to be included in the test set. Results for this set indicate that G3 theory performs significantly better than G2 for molecules containing Ca. When the 47 third-row systems are added to the G3/99 database the complete G3 average absolute deviation becomes 1.06 kcal/mol for 423 energies.
Databáze:	OpenAIRE
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