Theoretical studies of low-lying electronic states of lithium, titanium, and mercury compounds

Ground and low-lying excited electronic states of lithium, titanium and mercury compounds were investigated using high-level ab initio and density functional theory methods. Two Cs-symmetry triply hydrogen bridged equilibrium structures of Ti2H6 and Ti2 H+5 were obtained at the GVVPT2 level of theory. Twelve low-lying 1A' and 1A" states were calculated at both the GVVPT2 and MRCISD levels. A weakly coordinating H2 unit was observed for the Ti2 H+5 system, which seems to suggest that, subject to further studies, polyhydrido dititanium hydrides could serve as suitable precursors for hydrogen storage materials.;Studies of the Li+2 system in a high intensity laser field show a rich pattern of interactions involving its six lowest-lying electronic states, with photodissociation into the 2 S+u2 channel predicted to be a possibility. We also predict possible one-color experiments using 1.28 eV laser pulses from higher rovibrational levels of the Li+2 ground state. Given the vibrational period of Li+2 of 125 fs, it might be possible to control the Li(2p)/Li(2 s) branching ratio using modern femtosecond lasers.;High accuracy equilibrium geometries of ground and several low-lying excited states of Li3 plus vertical and adiabatic excitation energies were also calculated at the MRCISD level. Geometries of the excited states and adiabatic excitation energies were determined for the first time.;Simulations of coal combustion reactions involving Hg0 and Cl- on the activated carbon (AC) surface using the MPW3LYP variant of DFT revealed that the overall oxidation of Hg0 on an AC surface appears to be favored more on sites with a high positive charge density than sites with low charge density. The reactions were thermodynamically more favorable for aliphatic coal-mimetic molecules than the aromatic ones under room temperature and pressure conditions. Calculated rate constants were of the order of 1014 to 1015, which seems to suggest that extremely fast kinetics could be involved in these surface reactions.;The methane dissociation potential was predicted using the GVVPT2 method; our results showed excellent agreement with high-level MRCI techniques and were much improved over many-body perturbation theory methods.;The stereochemistry of turraesterodione was also predicted using MP2 and B3LYP; the results being in very good agreement with a recent X-ray study.