AB initio SCF and CI calculations of linear and bent acetylene

✍ Scribed by Wolf Ekkehard Kammer

• Publisher: Elsevier Science
• Year: 1970
• Tongue: English
• Weight: 429 KB
• Volume: 6
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(70)85213-7

✦ Synopsis

Ab initio SCF MO and CI calculations on acetylene in linear and bent conformations are reported. It is found that acetylene possesses stable truns-and c&-isomers for most of its low-lying electronicatly excited states.. The calculated transition energies are discussed in relation to the observed optical absorption bands and to electron-impact excitation energies.

The electronic structure of the acetylene molecule C2H2 has been the subject of numerous investigaticns by both semi-empirical and theoretical methods [l-lo].

Calculations of the electronically excited states of C2Hz have thus far been restricted almost exclusively to the molecule in its linear nuclear arrangement, and the results of these treatments differ with respect to the ordering of energy levels and their respective spacing.

Very little theoretical information is available about acetylene in bent conformations, especially with respect to the existence of stable transand cis-isomers.

-4 first attempt at calculating C2H2 in bent geometries was a six-electron ASMO calculation by Howard and _ E;"f;

[ll]; #is treatment found the excited tra?zs-1 Au state, but not the 1 lA2 state, in the cis-conformation, to be lower in energy than the corresponding linear 1 1 C; and also the ~~QJZS -and cis -states of llBu and llB symmetry to be more stable than the linear !I_ 1 A, which they correlate with.