Multireference configuration interaction treatment of potential energy surfaces: symmetric dissociation of H2O in a double-zeta basis
✍ Scribed by Franklin B. Brown; Isaiah Shavitt; Ron Shepard
- Publisher
- Elsevier Science
- Year
- 1984
- Tongue
- English
- Weight
- 630 KB
- Volume
- 105
- Category
- Article
- ISSN
- 0009-2614
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✦ Synopsis
Multiconfiiuration
SCF and multircferenoe Cl calculations have been performed for the Hz0 molecule in a double-zeta basis for four symmetric geometries, for comparison with fult CI results Unlike single-reference results. the energy errors are almost independent of geometry. allowing unbxased treatments of potential energy surfaces-1. Introrluction Minimal basis set full CI calculations for the electronic structure of small molecules (e-g. ref. [l] ) were used in the past to test the convergence and limitations of various methods for computing electron correlation energies, such as truncated and selected CI [ 11, perturbation-based approximations [2], and coupled cluster (CC) methods [3] _ However, minimal basis sets provide very little scope for a realistic description of correlation, and tests based on them cannot be considered as sufficiently indicative of the behavior of calculations using more adequate bases. Convergence studies have been carried out for some larger bases (see, eg. ref. [4] for truncated CI and ref. [S] for MBPT and CC), but in the absence of fuIl CI energies for these cases, assessment of the results obtained at each Ieve of approximation is more difficult. Recently, full CI results have become available for several small molecules (BH, H,O, NH,, HF) with double-zeta (DZ) and (for BH and HF) double-zeta-