Bonding and density functional studies of ABH2 (A,B=Al,Si,Ga,Ge) systems

  • Amanda Katherine Kernohan

    Student thesis: Other thesis - CDU

    Abstract

    This thesis had two main thrusts to it. The section that was approached first, mainly due to the large computational time required, was to investigate the use of density functional methods for predicting the properties of group 13 and 14 hydrides and related compounds. Initially, a wide range of functionals, at the DZP basis set, were used to study Si2H2, AI2H2> Ga2H2, Ge282> A1GaH2 and SiGeH2• These systems have a rich range of isomers within 20 - 30 kcalmol-1 of the ground state, making them ideal to analyse. From this -study, the most successful functionals were found to be BLYP, BP86 and the three hybrid methods B3LYP, B3P86 and B3PW91. These density functional methods were then used in conjunction with the TZP and TZVP basis sets. For the BLYP method, which is probably the most widely used, to date,Jour additional basis sets were used, namely the TZP, TZVP, TZ2P and TZV2P. Additionally, the digallane (Ga2H6) system was studied at all five different methods using all five different basis sets. Although there were some apparent deficiencies, these density functional methods were found to be reasonably accurate as a means of study. The second thrust to this study was to investigate the nature of bonding in the systems that were studied, by utilising some graphical routines. One technique that was used was the Bader method of "Atoms in Molecules", while others included plots of the canonic and localised molecular orbitals. From these localised molecular orbitals, it was seen that the nature of bonding in the systems correlates quite nicely with the proposals put forth by Roger Grev. 

    Note: Full text restricted.
    Date of Award1997
    Original languageEnglish
    SupervisorJames Mitroy (Supervisor)

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