Correlation energy contribution to the ammonia inversion barrier

✍ Scribed by N.C. Dutta; M. Karplus

• Publisher: Elsevier Science
• Year: 1975
• Tongue: English
• Weight: 674 KB
• Volume: 31
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(75)85063-9

✦ Synopsis

Diagmmmaric many-body doubleperturbation

theory is used to study the corrrlntion contibuti~n to the invetio;l bxrierin ammonia. With a one-center solution as the zero-order function, the perturbation energy d&rams are shown to be of three types: Hartrez-Fock diagrams (geometry dependent), atom-like correlation diagms (geometry independent) and non-atom-like correlation diagrams beometiy dependent). Only th: third class of diagrams enter into the carrekttion correction to the barrier. 'These diagrams, which appear first in third order; contribute a small fraction (1%) of the total correlation energy. We estimate from them that the correlation endrgy contribution to the barrier is small (less ;han iO% of the total barrier), although ,the bond length dependence of the correlation correction is such Gat it is difficult to cbtzin an exact value for it.