ISSN:
1573-9171
Schlagwort(e):
Hartree-Fock-Roothaan method
;
Möller-Plesset perturbation theory
;
polyradicals
;
geometric structure
;
heats of formation
;
hydrides of alkali metals
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
Notizen:
Abstract Calculations of the C3H6 · LiH, C4H8 · M+, and C4H8 · MH systems and of C2H2 · MH complexes (M = Li or Na) were carried out by the unrestricted Hartree-Fock-Roothaan (UHF) method with partial optimization of the geometry using fixed geometric parameters of the C3H6 and C4H8 molecules. The standard 3-21G and 6-31G* basis sets were used. Unlike the C3H6 · LiH structure, the C4H8 · M+ and C4H8 · MH systems are typical complexes. It was found that the C4H8 · M+, C4H8 · MH, and C2H2 · MH complexes are similar in coordination of M+ ions and MH molecules by carbon atoms in spite of considerable differences in the interatomic distances (−1 A) between these atoms in the C4H8 and C2H2 molecules. The heats of formation (Q), which were calculated in the UHF/6-31G* approximation and using second- and fourth-order Möller-Plesset perturbation theory taking into account the electron correlation energy in the MP2/6-31G*. MP4(SDQ)/6-31G*, and MP4(SDTQ)/6-31G* approximations, satisfy the following relationships: Q(C2H3 · MH) 〈 Q(C4H8 · MH) 〈 Q(C4H8 · M+). It was observed that in going from Li to Na the corresponding values of Q tend to decrease.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF01431784
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