ISSN:
0020-7608
Keywords:
Chemistry
;
Theoretical, Physical and Computational Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Electronic structures and properties of carbides MC, M5C (M=Fe, Ni, Cu), and TiC and Ti7C were studied using density functional methods (DF), particularly the local density approach (LDA) with the Vosko-Wilk-Nusair (VWN) correlation functional, the generalized gradient approximation (GGA) of Becke and Perdew (using Becke's 1988 exchange functional and Perdew's 1986 correlation functional - BP86), and the ADF program of Baerends et al. In the first part of this report, we studied equilibrium geometries and dissociation energies for the process MC→M+C involving the doublet ground state for M=Cu, singlet and triplet states for M=Ni, and triplet and quintuplet states for M=Fe, Ti. Charge distributions by population analysis, dipole moments, and vibrational frequencies were also evaluated. All calculations were done using triple-zeta basis sets, with frozen-core orbitals and the GGA corrections. In the second part of this report, we consider the doublet states of Cu5C and singlet and triplet states of Ni5C, taking planar and nonplanar models for the M5 clusters. The triplet and quintuplet states of Fe5C were studied with a nonplanar model for the Fe5 cluster, whereas in the case of the triplet and quintuplet states of Ti7C, a Ti7 planar model was chosen. Optimization of the position of the C atom in the cluster, dissociation energies, distribution of charges in the molecule, and dipolar moments were also analyzed, and comparisons with the results obtained for the corresponding carbides (MC) were made. These results, together with the ones of the corresponding carbonyls - that have previously been done by the same methodology - provide us with an interesting comparison of the M(SINGLE BOND)C bond dissociation energy in carbides and carbonyls. Calculations of the C(SINGLE BOND)O bond dissociation energies for the MCO and MnCO compounds were also performed. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 65: 919-928, 1997
Additional Material:
6 Tab.
Type of Medium:
Electronic Resource
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