Al <sub> 4 </ Sub> H <sub> 4 </ Sub>, Of Al <sub> N </ Sub> H-<sub> N +2 </ Sub>, (4 ¡Ü N ¡Ü 8) The Ground State And Its Calculation Of Excited State Properties

The geometric configurations, electronic properties and low-lying excited states of the aluminum hydride clusters Al₄H₄, Al_nH_n+2, (4≤n≤8) and their corresponding anions have been studied using the density functional theory (DFT),We have optimized the geometric structures of Al₄H₄, Al_nH_n+2, (4≤n≤8) and their corresponding anions without any symmetry constraint. The calculations show that the ground state structures of Al₄H₄, Al₄H₄^-, Al₄H₆, Al₄H₆^- ,Al₅H₇^- and Al₈H₁₀ gotten by us are the same as those optimized by Grubisic et al, however, the ground state structures of Al₅H₇, Al₆H₈, Al₆H₈^-, Al₇H₉, Al₇H₉^- and Al₈H₁₀^- we got have lower energy than that got by Grubisic et al. The corrections what we obtained have been comfirmed by analysing their total energies, frequencies, adiabatic electron affinity (EAa) and vertical detachment energy (VDE) of the compunds.The vertical detachment energy (VDE) of aluminum hydride cluster anions, Al₄H₄^-, Al_nH_n+2^-, (4≤n≤8) and the adiabatic electron affinity (EAa) of the corresponding neutral species have been calculated by both PW91 functional at TZVP level and B3LYP functional at 6-311++G (d,p) level respectively. We found that the values of calculation with B3LYP/ 6-311++G (d,p) are in good agreement with that of experiment.Time-dependent density functional theory (TD-DFT) is used to calculate the excited states. A theoretical assignment at the B3LYP level for the features in the experimental photoelectron spectra (PES) is given. Our results compare well with the available experimental values.