Multireference Configuration Interaction (MRCI) is widely and successfully used for the accurate computation of molecular energies and properties when chemical bonds are broken, and in other cases of quasi-degeneracy. However, it suffers from a lack of extensivity, which introduces significant errors for large molecules. Currently feasible Multireference Coupled Cluster (MRCC) approaches, which address the extensivity issue, are complicated and expensive. In this work we investigate simple approximations to MRCC, generalising the single-reference linked pair functional theories to the multi-reference case. We show how to develop a simple extension to MRCI that gives approximate extensivity, retains orbital invariance and acts as an approximation to a multireference variational Coupled Cluster theory.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:610989 |
| Date | January 2013 |
| Creators | Jenkins, Andrew |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/59800/ |
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