Calculation of the fourth-order triple-excitation contribution to MB RSPT by using spatial symmetry properties of molecules
✍ Scribed by J. Noga
- Book ID
- 103046223
- Publisher
- Elsevier Science
- Year
- 1983
- Tongue
- English
- Weight
- 513 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0010-4655
No coin nor oath required. For personal study only.
✦ Synopsis
A new algorithm is described for calculating the triple-excitation contribution to the fourth-order Many-Body Rayleigh-Schrodinger Perturbation Theory (MB RSPT). Exploitation of spatial symmetry properties of molecules is an inherent feature. Evaluation of zero intermediate values is eliminated from the calculation at the very Outset of the program by a single numerical test of integrals. The algorithm is very efficient particularly in calculating electron correlation energies of symmetric molecules; but it can be applied successfully to calculate energies of arbitrary closed shell systems. It does not require much storage, since only a small fraction of the non-zero integrals must be held in core memory at the same time. Some examples of applications are appended. The method can be applied to calculate each contribution to MB RSPT.