Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


The linear combination of Gaussian orbitals (LCGO) method has been adopted in developing a spin-polarized molecular orbital calculation code. The calculations are based on density functional theory using local density approximation for the exchange-correlation potential. A variational fitting method is used to obtain a charge density fit to avoid the need for using four-center integrals in evaluating the Coulomb potential. The matrix elements of the exchange potential are evaluated by direct numerical integration using a doubling grid developed for this purpose. Self-consistent solutions have been obtained using this method for Fe(,9) and Fe(,15) clusters with open boundaries and with body-centered cubic symmetries. The convergence of several properties to those of bulk has been examined, and a good similarity could be obtained between the bulk density of states and that of Fe(,15) confirming the result obtained from the multiple-scattering (MS)-X(alpha) method. The charge and spin densities for the central atom were found to be very different from those of bulk iron in agreement with the results reported by other authors. However, present results seem to exhibit stronger tendency of minority-spin electron flow to the central site than was obtained by MS-X(alpha) method. The ionization potential of the Fe(,9) cluster is determined by the transition state method and good agreement with experiment is obtained. Fe(,8)C and Fe(,14)C clusters have also been considered to study impurity effects in clusters.