Frozen core and virtual orbitals in the MC SCF theory
✍ Scribed by M. Hada; H. Yokono; H. Nakatsuji
- Publisher
- Elsevier Science
- Year
- 1987
- Tongue
- English
- Weight
- 572 KB
- Volume
- 141
- Category
- Article
- ISSN
- 0009-2614
No coin nor oath required. For personal study only.
✦ Synopsis
An efficient approximation in the multiconfigurational self-consistent field (MC SCF) method is presented for calculations on large systems. In this method, the orbitals are spanned by adequate orthonormal orbitals, such as Hartree-Fock orbitals, instead of by the entire set of basis functions, and certain of these are not included in the orbital optimization. These include the core orbitals and high-energy virtual orbitals selected from the Hartree-Fock manifold. The computational time for MC SCF calculations dramatically decreases without significant loss of accuracy. This saving in computer time is primarily due to the reduction in the size of the integral transformation. Test calculations are performed for Scz, CO, and acetylene, and the accuracy of the energy and the Hellmann-Feynman force are checked.