ISSN:
0192-8651
Keywords:
Computational Chemistry and Molecular Modeling
;
Biochemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Computer Science
Notes:
Dissociation energies and potential energy surface features for the carbon clusters C2 to C10 are compared with ab initio or experimental results for the semiempirical methods MINDO/3, MNDO, AM1, and PM3. Quite surprisingly, MINDO/3 gives a rather good account of the various structures and electronic states, unlike the other three methods. MINDO/3 tends towards systematic overestimates of binding energies, the other methods to systematic gross underestimates. Reparametrization of the diatomic parameters α, βs, and βp for exact reproduction of the experimental data for C3 results in much improved values for binding energies, but fails to correct the state splittings. Also reparametrizing Uss, Upp, ζs, and ζp to reproduce the ab initio linear-rhombic energy difference in C4 results in a much improved description of the other states. For the linear structures, computed harmonic frequencies with the latter parameters are in surprisingly good agreement with experimental or correlated ab initio data, where available; experimental values are consistently overestimated by about 40 cm-1. Other results are comparable in quality to good ab initio treatments. The experimental IR bands at 2128 and 1892 cm-1, formerly assigned to C9, should be reassigned to linear C7. The intense 1997 cm-1 feature almost certainly belongs to C9; bands at 1952 and 1197 cm-1 both belong to linear C6. Tentative assignments of bands in the 1600-1850 cm-1 region to various cyclic structures of C6, C8, and C10 have been made. As such, this suggests a new and promising procedure for the theoretical study of large molecules in general, and of large clusters in particular.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jcc.540120107
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