| Local-density-functional (LDF) electronic structure methods provide an appealing alternative to ab initio methods for studying inorganic molecular systems. The history of LDF theory and computational implementations is reviewed, with emphasis on Slater's X{dollar}alpha{dollar} exchange-only functional.; Previous applications of the X{dollar}alpha{dollar} method to compounds containing metal-metal multiple bonds are discussed. Results of X{dollar}alpha{dollar}-SW and various DV-X{dollar}alpha{dollar} calculations on symmetric quadruply bonded Mo{dollar}sb2{dollar}L{dollar}sb4{dollar}X{dollar}sb4{dollar} compounds are compared. Use of the DV-X{dollar}alpha{dollar} method with an accurate charge fitting scheme is required to describe the optical spectra of these compounds, but the more primitive X{dollar}alpha{dollar}-SW method is adequate for qualitative consideration of metal-metal bonding. The X{dollar}alpha{dollar}-SW method is used to analyze the metal-metal bonding in asymmetric (HO){dollar}sb4{dollar}MoMo(PH{dollar}sb3)sb4{dollar} and Cl{dollar}sb4{dollar}MoMo(PH{dollar}sb3)sb4{dollar}. The differing {dollar}pi{dollar}-donor abilities of the alkoxide and chloride ligands significantly alters metal-metal bonding in these two models.; Non-relativistic and relativistic DV-X{dollar}alpha{dollar} calculations are used to examine the structural and spectroscopic properties of the M{dollar}sb2{dollar}(OMe){dollar}sb{lcub}10{rcub}{dollar} (M = Ta, W, Re) series. The non-relativistic results adequately explain the ligand conformational changes as a function of metal atom. The M{dollar}sb2{dollar}(OMe){dollar}sb{lcub}10{rcub}{dollar} compounds are found to possess metal-metal bonds, while the isostructural M{dollar}sb2{dollar}Cl{dollar}sb{lcub}10{rcub}{dollar} compounds do not, because of the directional {dollar}pi{dollar}-donating ability of methoxide ligands. Relativistic DV-X{dollar}alpha{dollar} calculations are used to assign the photoelectron and optical spectra of the M{dollar}sb2{dollar}(OMe){dollar}sb{lcub}10{rcub}{dollar} compounds.; Relativistic DV-X{dollar}alpha{dollar} calculations are used to examine the electronic structure of three-coordinate actinide compounds AnX{dollar}sb3{dollar} (An = Th, U, Pu; X = H, CH{dollar}sb3{dollar}, NH{dollar}sb2{dollar}, and OH). Actinide-ligand {dollar}sigma{dollar} bonding is mediated by the metal-based s, p, and d orbitals, while actinide-ligand {dollar}pi{dollar}-bonding can involve significant f orbital contributions. Models are developed to describe the interplay of spin-orbit and ligand field effects in these molecules. The results are also extended to model four-coordinate systems, including UH{dollar}sb4{dollar}, HU(NH{dollar}sb2)sb3{dollar}, and U(NH{dollar}sb2)sb4{dollar}.; Finally, the Hartree-Fock method is used to examine substituent effects in borinium cations (BF{dollar}sbsp{lcub}2{rcub}{lcub}+{rcub}{dollar}), borenium cations (BR{dollar}sb2{dollar}L{dollar}sp+{dollar}), and boranes (BR{dollar}sb3{dollar}). Substituent preferences vary widely among the three and are dependent on the {dollar}sigma{dollar}- and {dollar}pi{dollar}-donor properties of R. The heterolytic B-L bond energy is directly related to the proton affinity of L. |
