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Approximate ab initio calculations and the method of molecular fragments

Brailsford, David F.

Authors

David F. Brailsford



Contributors

V R Saunders
Editor

J Brown
Editor

Abstract

A two stage approach to performing ab initio calculations on medium and large sized molecules is described. The first step is to perform SCF calculations on small molecules or molecular fragments using the OPIT Program. This employs a small basis set of spherical and p-type Gaussian functions. The Gaussian functions can be identified very closely with atomic cores, bond pairs, lone pairs, etc. The position and exponent of any of the Gaussian functions can be varied by OPIT to produce a small but fully optimised basis set. The second stage is the molecular fragments method. As an example of this, Gaussian exponents and distances are taken from an OPIT calculation on ethylene and used unchanged in a single SCF calculation on benzene. Approximate ab initio calculations of this type give much useful information and are often preferable to semi-empirical approaches, since the nature of the approximations involved is much better defined.

Citation

Brailsford, D. F. (1975). Approximate ab initio calculations and the method of molecular fragments. In V. R. Saunders, & J. Brown (Eds.),

Conference Name Quantum Chemistry - The State of the Art
End Date Apr 10, 1974
Publication Date Jul 1, 1975
Deposit Date Aug 4, 2005
Publicly Available Date Mar 28, 2024
Journal Quantum Chemistry - The Stae of the Art. Proceedings of SRC Atlas Symposium April 1974
Peer Reviewed Peer Reviewed
Volume 4
Series Title SRC Atlas Symposium
Keywords SCF, Molecular orbitals, Gaussian functions, molecular fragments
Public URL https://nottingham-repository.worktribe.com/output/1025738
Additional Information This is a re-built PDF version of the "final draft" of this conference paper.

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