Comparison of Morokuma and Perturbation Theory Approaches to Decomposition of Molecular Interaction Energy. (NH4)+...NH3

Authors

Sławomir M. Cybulski
Steve Scheiner, Utah State UniversityFollow

Document Type

Article

Journal/Book Title

Chemical Physics Letters

Publication Date

2-1990

Publisher

Elsevier

Volume

166

Issue

1

First Page

57

Last Page

64

Abstract

The interaction energy between NH₄⁺ and NH₃ is decomposed for a range of intermolecular separations within the context of a variety of basis sets including 6-31G**, 6-31+G**, and Sadlej polarization sets of type [5s3p2d/3s2p], including a set of f-functions as well. The electrostatic component dominates the interaction in all cases. At separations near the minimum or closer, the Morokuma second-order components (POL and CT) blow up. In contrast, ΔE_SCF^def, representing mutual polarization and orbital relaxation, is in good agreement with the induction energy computed via perturbation theory. Correction of the superposition error is noted to be important for this agreement and, indeed, for all components. In fact, following this correction, even the smaller sets provide accurate measures of the exchange term. The second-order correlation correction to the electrostatic interaction ϵ_es¹² is computed and found to be fairly small. The dispersion energy embodied in ϵ_disp²⁰ is considerably larger than the latter term and grows in proportion to the flexibility of the basis set.

Recommended Citation

Cybulski, Sławomir M. and Scheiner, Steve, "Comparison of Morokuma and Perturbation Theory Approaches to Decomposition of Molecular Interaction Energy. (NH4)+...NH3" (1990). Chemistry and Biochemistry Faculty Publications. Paper 569.
https://digitalcommons.usu.edu/chem_facpub/569