THEORETICAL INVESTIGATIONS OF THE SPECTRUM OF POTASSIUM-MOLYBDENUM- HEXA FLUORIDE (SCF, TRANSITION)

MARK JEROLD BLACKMAN, Purdue University

Abstract

This work extends previously developed theoretical methodology for the first transition series of elements to the second. A critical analysis of the experimental spectrum and crystal structure of K(,3)MoF(,6), in light of more recent developments in synthesis and structural determinations of Mo('3+) compounds is given. The methodology for this ab initio, strong field, Hartree-Fock-Roothaan SCF computation and the development of basis sets for atoms and ions of the second transition series is reviewed. Computations following this methodology are interpreted and compared to existing theoretical and experimental results for Cr('3+) and Mo('3+) cluster spectra. Detailed discussion of the nature of the bonding of the MoF(,6)('3-) cluster and the spectrum of the free cluster and K(,3)MoF(,6) is provided. A Correlation Energy Correction (CEC) and computed atomic spectrum for the Mo('3+) ion are given. A simple model for the external cluster potential is also provided. Spectra are computed with and without external cluster potential, CEC, limited configuration interaction of the d('3) states and spin-orbit interaction. The best theoretically predicted results are 25.9 kK for the ('4)T(,2g) transition and 30.3 kK for the ('4)R(,1g) transition. The experimental spectrum gives bands at 23.5 kK and 29.7 kK which have been assigned to these transitions. However, the theoretical spectrum was computed at a metal-ligand separation of 3.90 Bohr, more in line with more recent structural determinations of compounds containing the MoF(,6)('3-) cluster. A band at 38.2 kK in the experimental spectrum is thought to be a La Porte allowed band of contaminating Mo('5+) in the experimental sample. The conclusions drawn from this work are that this theoretical methodology is valid for second transition series elements and that because of unexpected differences in the chemistry of Cr('3+) and Mo('3+) cluster compounds, a great number of presently accepted theoretical and experimental findings for clusters of the Mo('3+) require either reexamination or redetermination.

Degree

Ph.D.

Subject Area

Chemistry

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