Improved transformation algorithm of two-electron integrals from atomic orbital basis to a symmetry orbital basis
✍ Scribed by Toshikazu Takada; Fukashi Sasaki
- Publisher
- John Wiley and Sons
- Year
- 1980
- Tongue
- English
- Weight
- 382 KB
- Volume
- 18
- Category
- Article
- ISSN
- 0020-7608
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✦ Synopsis
Abstract
The transformation of two‐electron integrals from an atomic orbital basis to a symmetry orbital basis is a straightforward procedure, but becomes a time‐consuming process when the system has high symmetry. In the conventional transformation algorithm, the number of multiplications is proportional to the fifth power of the basis size. To reduce the computer time, a new transformation algorithm is proposed. In this method, the number of multiplications for the transformation is proportional to the fourth power of the number of atomic orbitals in an equivalent orbital group. A new transformation program has been completed and tested against the conventional n^5^ method. The present method may be regarded as extension of Almlöf's method to any molecular point group. The program cuts the CPU time for the transformation to one‐third in calculations for C~4~H~8~ and NiF~6~. This reduction is quite significant for large systems having high symmetry.