NMR study of internal rotations and phase transitions in lithium borohydride and borodeuteride

By 2H, 7Li and 11B NMR pulsed method polycrystal LiBN4 and LiBD4 in the temperature range of 145-404 K have been studied. In the range of 385-396 K the time of spin-lattice relaxation of 11B and 2H undergoes irregular changes. Values of activation energy and preexponential multiplier of reorientation motion of (BH4)- and (BD4)-anions are determined. Constants of quadrupole bonds on 7Li nuclei in LiBH4 and LiBd4 are measured, the values of which do not vary in the temperature range from 333 K to 400 K and constitute 36.8±0.4 and 37.0±0.4 kHz respectively