Many Body Perturbation Theory Using a Restricted Open-Shell Hartree-Fock (ROHF) Reference Function
Abstract
One of the most common reference functions used for open shell molecules is the unrestricted Hartree-Fock (UHF) reference. While this reference is useful for many molecular systems, it can sometimes suffer from the mixing of high multiplicity states into the state of interest. This phenomenon is termed spin contamination. A number of projection techniques have been developed to correct the UHF reference at the SCF and correlated levels. General implementation of gradients for these projected methods, however, can be complex and computationally expensive. Nor are such methods rigorously extensive, as required for many-electron methods. These facts limit the usefulness of these methods. This work presents the development of an alternative approach. Rather than attempting to correct the deficiencies in the UHF reference, we start with a reference (ROHF) which is an eigenfunction of spin. The treatment of electron correlation is introduced using many body perturbation theory (MBPT), which is perhaps the most efficient way of adding the critical effects of electron correlation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1991
- Accession Number
- ADA249725
Entities
People
- Walter J. Lauderdale
Organizations
- Air Force Institute of Technology