ON THE CONFIGURATION OF THE [NIH4] COMPLE X IN CUBIC MG2NIH4 STRUCTURE

The configuration of the [NiH4] complex in cubic Mg2NiH4 structure has been investigated by using relativistic density-functional method, Th e crystalline environment was simulated by a cut-off type Madelung pot ential, A square planar configuration of NiH42- and a tetrahedral conf iguration of NiH44- are assumed, respectively in the calculations. For the square planar configuration, a good agreement of the calculated b ond length and force constant with experimental ones was obtained. How ever, the calculation on the tetrahedral configuration yielded too sho rt Ni-H bond length and too large Ni-H farce constant. The comparison between the calculated results and experimental ones gives a clear pre ference of the square NiH42- configuration over the tetrahedral NiH44- configuration in the cubic Mg2NiH4 structure.