Ab initio SCF study of OHO3- system and its relation to the structure of alpha-Al2O3 : OHO3-(Me2+)

SCF calculations using an extended basis set were carried out for linear configurations of the system O-H-O3- with O-O distances R = 2.87, 2.73, 2.62 and 2.52 A and variable O-H distance r. SCF total energies, electron density charts and potential functions are discussed. The potential function exhibits a single minimum for R <= 2.52 A and has two minima for R > 2.6 A in close agreement with recent empirical findings about potential functions of H bonds. Using crystal field calculations for a point charge model, the potential functions of the proton between oxygen ion pairs in various sites of the alpha-Al2O3 structure are calculated and used for numerical determination of energy levels and transition frequencies of the Linear vibrational mode of the OHO3-:alpha-Al2O3 system. Comparison with observed IR absorption bands of alpha-Al2O3:Fe2+, H+ (R = 2.87 A) and alpha-Al2O3:Co2+, H+ (R = 2.73 A) yields qualitative agreement of transition frequency. Satisfactory interpretation of the widely varying line width of the nu(OH) band of OHO3- in different sites may be given in terms of anharmonicity, but the existence of several bands remains unexplained.