Various forms of multi-reference perturbation theory, including our recently suggested 'invariant' form are compared for some diatomic supermolecules. While the 'invariant' zeroth-order Hamiltonian is not the direct sum of the zeroth-order fragment Hamiltonians, the size consistency errors in the fi
Low-spin open-shell perturbation theory
✍ Scribed by Jamie S. Andrews; Christopher W. Murray; Nicholas C. Handy
- Publisher
- Elsevier Science
- Year
- 1993
- Tongue
- English
- Weight
- 575 KB
- Volume
- 201
- Category
- Article
- ISSN
- 0009-2614
No coin nor oath required. For personal study only.
✦ Synopsis
A perturbation theory appropriate for low-spin open-shell systems introduced by Murray and Davidson is investigated at second order. Matrix formulas are given and applications to NH, OH+, Oz. CH2 and H&O are reported. The results suggest that this perturbation theory is eauivalent in accuracy to those currently in use for closed-shell and high-spin open-shell systems. 'Al DZP -113.893873 'A, TZZP -113.912364 'A" DZP -113.816468 XA" TZZP -113.832506 'A" DZP -113.806347 'A" TZ2P -113.822479 a) Geometries taken from ref. [ 331.
📜 SIMILAR VOLUMES
A new open-shell perturbation theory is formulated in terms of symmetric spin orbitals. Only one set of spatial orbitals is required, thereby reducing the number of independent coeffmients in the perturbed wavefunctions. For second order, the computational cost is shown to be similar to a closed-she
A method is given for eliminating the off-diagonal lqrangian multipliers which appear in open-shell SCF theory. This lcads to a set of coupled eigenvalue equations which is easily solved for a new guess to the SCF orbit&. This proccdurc has proven more conveient than many others now in use.