A perturbative correction to restricted open shell configuration interaction with single substitutions for excited states of radicals

✍ Scribed by Martin Head-Gordon; David Maurice; Manabu Oumi

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 568 KB
• Volume: 246
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(95)01111-l

✦ Synopsis

A perturbative correction, termed RCIS (D), to restricted open shell single excitation configuration interaction (ROCIS) is formulated and implemented for excited states of radicals. RCIS(D) gives spin-pure energies (but not wavefunctions), is size-consistent, and has computational complexity scaling with the fifth power of molecular size. All these properties are analogous to second order restricted M¢ller-Plesset theory for the ground state. Comparison of calculated vertical excitation energies against experiment for a diverse series of small radicals, Bell, BeF, CH, CH3, CN, CO +, NO and OH, suggests that RCIS(D) constitutes a useful improvement over ROCIS.