Symmetrized Normal Mode Analysis of the Spin–Lattice Relaxation of Metal Borohydrides in Solids

摘要

The spin–lattice relaxation of a quadrupolar nucleus 11B of solid borohydrides was measured by using solid‐state NMR techniques and the experimental data were analyzed with a newly‐constructed relaxation matrix. The spectral densities for dipole–dipole, quadrupolar, and random‐field interactions were obtained, and the quadrupolar contribution to the spin–lattice relaxation of 11B nucleus of solid borohydrides were calculated as well. The quadrupolar contribution was less than 10% in solid LiBH4, as has been reported. In addition, the quadrupolar contribution was more than 30% in solid Mg(BH4)2, as was expected. The symmetrized normal mode analysis for the spin–lattice relaxation of a quadrupolar nucleus could provide more accurate spectroscopic parameters, and is expected to improve accuracy of the description of the rotational motion of the local chemical unit containing the quadrupolar nucleus.