ABSTRACT:The electronic structure and properties of the carbonyls TiCO, FeCO, and NiCO in the quintuplet, triplet, and singlet ground states and triplet, quintuplet, and triplet first electronic excited states, respectively, were studied using density functional Ž . Ž . theory DFT methods. The ADF program version 2.1 with the parameterizations BP86, Ž . Ž . BPW91, and BLYP for the GGA corrections and the Slater-type orbital STO basis sets IV as well as the GAUSSIAN 94 program with the parameterizations BP86, PW91, BLYP, Ž . B3PW91, and B3LYP and the Gaussian basis sets 6-311G d, p were used. Similar calculations were done on the carbenes TiCH , FeCH , and NiCH in the triplet, triplet, 2 2 2 and singlet ground electronic states and the quintuplet, quintuplet, and triplet first electronic excited states. Geometry optimization and the calculation of dissociation energies for the M-C bond, vibrational frequencies, electric atomic charges, and dipole moments were performed for these compounds in the above-mentioned states, and comparisons between the results obtained as well as with those reported in the literature were made.

Electronic structures and properties of carbides MC, M C M s 5 7 7chosen. 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 Ž . 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-C bond dissociation energy in carbides and carbonyls. Calculations of the C-O bond dissociation energies for the MCO and M CO compounds were also n performed.

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Density functional theory (DFT) calculations of the electronic structure and properties of Fe, Ni, and Cu carbonyls with one and five transition‐element atoms are reported, due to their importance in heterogeneous catalysis (especially in Fischer‐Tropsch synthesis). The local density approximation (LDA) with the Vosko‐Wilk‐Nussain (VWN) correlation functional as well as the generalized gradient approximation (GGA) using Becke's 1988 exchange functional and Perdew's 1986 correlation functional (BP method) were applied to the study of the clusters using a triple‐zeta plus polarization (TZP) basis set. Triplet and quintuplet states for FeCO, singlet and triplet for NiCO, and doublet for CuCO were considered, and optimization of energy at the LDA/BP level for these cases was done. Dissociation energies in M and CO fragments, frequencies, and population analysis were performed. Geometry optimization of the distance between the C atom and the clusters M5 (with geometries taken from the crystals) were carried out and the dissociation energy in fragments M5 and CO as well as population analysis at the optimized geometries were also done. Comparison between our results and some others published using ab initio and density functional methods were performed. © 1996 John Wiley & Sons, Inc.

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