ELECTRON-DINAMICAL CHARACTERISTICS AND STABILITY OF METAL HYDRIDES. R.P. Ozerov, A.V. Sazonov, A.V. Bochkarev, S.A. Samoilov and V.I. Khleskov, Mendeleev University of the Chemical Technology of Russia, Miusskaja Sq 9, 125047 Moscow, Russia

The X-ray diffraction data treatment, atomic and electronic structure as well as vibrational characteristics calculation have been attempted to be used in linking together the structure and stability of hydrides. The later represent the model matrices for hydrogen storage systems (in ecologically pure energetic) which must be stable enough not to loose hydrogen at room temperature and to let hydrogen go out at elevated temperatures.

There are 2 ways of the electron structure investigations. First, electron density can be measured using the accurate X-ray diffraction data. The experimental data [1,2] has been treated for LiH. The Hansen-Coppens multipole model has been used. Another way consists of the quantum chemical calculations. The iterative extended Huckel method with special parameterization for metal atoms has been employed for the calculation of zone structure and charge transfer in LiH, NiH and AlD₃. The cluster approach has been used with the maximum cluster size aapproximately 100 atoms.

The coincidence of the results was found to be good. The charge transfer of about 0.8 electron has been found.

The isotope exchange coefficient b in the reaction LiH(D)-H₂ has been calculated using the previous data. The method of moments of the frequency function has been worked out. The comparison of the calculated temperature dependence of b shows the good agreement with experimental one.

1. Calder, R.S., et al 1962, J.Phys. Chem. Sol. 23, 6212

2. Vidal-Valat, G., et al 1992 Acta Crystal. A48,46