%0 Journal Article
%A Whittier R Myers
%A Lin-Wang Wang
%A Thomas J Richardson
%A Michael D Rubin
%B Journal of Applied Physics
%D 2002
%G eng
%N 8
%P 4879-4885
%R 10.1063/1.1454206
%T Calculation of Thermodynamic, Electronic, and Optical Properties of Monoclinic Mg<sub>2</sub>NiH<sub>4</sub>
%V 91
%1 <p>Windows and Daylighting Group</p>
%2 LBNL-47519
%8 04/2002
%X <p><em>Ab initio</em> total-energy density functional theory is used to investigate the low temperature (LT) monoclinic form of Mg<sub>2</sub>NiH<sub>4</sub>. The calculated minimum energy geometry of LT&nbsp;Mg<sub>2</sub>NiH<sub>4</sub> is close to that determined from neutron diffraction data, and the NiH<sub>4</sub> complex is close to a regular tetrahedron. The enthalpies of the phase change to high temperature (HT) pseudo-cubic&nbsp;Mg<sub>2</sub>NiH<sub>4</sub> and of hydrogen absorption by Mg<sub>2</sub>Ni are calculated and compared with experimental values. LT&nbsp;Mg<sub>2</sub>NiH<sub>4</sub> is found to be a semiconductor with an indirect band gap of 1.4 eV. The optical dielectric function of LT Mg<sub>2</sub>NiH<sub>4</sub> differs somewhat from that of the HT phase. A calculated thin film transmittance spectrum is consistent with an experimental spectrum.</p>