The BERKELEY system. III. General configuration-interaction methods for open-shell molecular electronic states

✍ Scribed by Bernard R. Brooks; Henry F. Schaefer III

• Book ID: 104579384
• Publisher: John Wiley and Sons
• Year: 1978
• Tongue: English
• Weight: 482 KB
• Volume: 14
• Category: Article
• ISSN: 0020-7608
• DOI: 10.1002/qua.560140507

✦ Synopsis

Abstract

A system of general “open‐ended” configuration‐interaction (CI) programs, specifically designed for the Harris Corporation Slash Four minicomputer, is described. These methods are general in the sense that an arbitrary list of configurations (linear combinations of Slater determinants) may be used, and open ended in that peripheral (i.e., disk) storage capacity determines the maximum size problem that can be solved. The largest variational calculations carried out to date using BERKELEY involve 7064 open‐shell singlet configurations (31,898 Slater determinants). Detailed timing breakdowns are presented for four test cases, two of which involve the lowest ππ* singlet state of ethylene. The other two examples are the orthogonal or bisected singlet state of trimethylenemethane and the ^8^B~1~ state of the MnCH~2~ complex. In the latter case, it is found that the predicted MnCH~2~ dissociation energy is only slightly increased by electron correlation effects.