Effects of different substitution concentration and configuration on some properties of magnesium hydrides substituted with titanium; Ab initio study.

We investigated hydrogen some properties of magnesium hydrides substituted with titanium by a first principles calculation. In order to evaluate effect of different substitution concentration and configuration on desorption temperature and bulk modulus, we constructed five systems such as Mg 4 Ti 2 H 12 , Mg 8 Ti 2 H 20 , Mg 16 Ti 2 H 36 , Mg 14 Ti 4 H 36 and Mg 12 Ti 6 H 36 by using 1 × 1 × 3, 1 × 1 × 5 and 3 × 3 × 1 super cell of pure magnesium hydride. Among the investigated systems, Mg 14 Ti 4 H 36 system showed the best performance as hydrogen storage material in the complex viewpoints of substitution energy, desorption temperature and bulk modulus. In addition to, our results demonstrated that not only substitution concentration but also configuration plays vital effect on material's property of magnesium hydrides. Bader charge analysis explained the reason why desorption temperature is fallen down by substitution with titanium. • Overall bonding strength is weakened by titanium substitution. • Mg 4 Ti 2 H 6 has too low desorption temperature for dehydrogenation. • Proper substitution configuration is necessary for good property. • Mg 14 Ti 4 H 36 is a good candidate as hydrogen storage material. • Single substitution has advantages compared with co-substitution. [ABSTRACT FROM AUTHOR]