Approximate ab initio calculations and the method of molecular fragments
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 G...
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| Format: | Conference or Workshop Item |
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Science Research Council
1975
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| Online Access: | https://eprints.nottingham.ac.uk/163/ |
| _version_ | 1848790352525262848 |
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| author | Brailsford, David F. |
| author2 | Saunders, V R |
| author_facet | Saunders, V R Brailsford, David F. |
| author_sort | Brailsford, David F. |
| building | Nottingham Research Data Repository |
| collection | Online Access |
| description | 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. |
| first_indexed | 2025-11-14T18:11:15Z |
| format | Conference or Workshop Item |
| id | nottingham-163 |
| institution | University of Nottingham Malaysia Campus |
| institution_category | Local University |
| last_indexed | 2025-11-14T18:11:15Z |
| publishDate | 1975 |
| publisher | Science Research Council |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | nottingham-1632020-05-04T20:34:17Z https://eprints.nottingham.ac.uk/163/ Approximate ab initio calculations and the method of molecular fragments Brailsford, David F. 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. Science Research Council Saunders, V R Brown, J 1975-07 Conference or Workshop Item PeerReviewed Brailsford, David F. (1975) Approximate ab initio calculations and the method of molecular fragments. In: Quantum Chemistry - The State of the Art, 8-10 April 1974, St Catherine's College Oxford. SCF Molecular orbitals Gaussian functions molecular fragments |
| spellingShingle | SCF Molecular orbitals Gaussian functions molecular fragments Brailsford, David F. Approximate ab initio calculations and the method of molecular fragments |
| title | Approximate ab initio calculations and the method of molecular fragments |
| title_full | Approximate ab initio calculations and the method of molecular fragments |
| title_fullStr | Approximate ab initio calculations and the method of molecular fragments |
| title_full_unstemmed | Approximate ab initio calculations and the method of molecular fragments |
| title_short | Approximate ab initio calculations and the method of molecular fragments |
| title_sort | approximate ab initio calculations and the method of molecular fragments |
| topic | SCF Molecular orbitals Gaussian functions molecular fragments |
| url | https://eprints.nottingham.ac.uk/163/ |