Influence of alloying elements on the stability and dehydrogenation properties on Y(BH₄)₃ by first principles calculations

First principles calculations are performed to study the influence of alloying elements Li, Na, K, Ti, Mn, and Ni and Y vacancy on the stability and dehydrogenation properties of Y(BH₄)₃. The formation energies of low and high temperature (LT and HT) phases of alloyed Y(BH₄)₃ are evaluated. Ti, Mn, and Ni elements and the Y vacancy containing Y(BH₄)₃ systems are endothermic. The Y vacancy is difficult to be generated due to the high energy demand. The alkali metals of Li, Na, and K prefer to occupy the interstitial sites in both the LT and HT phases of Y(BH₄)₃, especially the K element. The K containing systems show negative formation energy, even if eight K atoms are introduced. The K containing systems show similar structure characteristics with the KY(BH₄)₄ compound. Therefore, a phase transition from the K alloyed Y(BH₄)₃ to KY(BH₄)₄ is expectable. However, the transition from Li/Na alloyed Y(BH₄)₃ to corresponding Li/Na-Y(BH₄)₄ compounds is energetically unfavorable. Electronic structures of alloyed Y(BH₄)₃ are investigated to explore the reasons that why only K alloyed Y(BH₄)₃ can transform to KY(BH₄)₄ compound. In term of dehydrogenation properties, all alloyed systems show smaller dehydrogenation energies than the pure Y(BH₄)₃. The concentrations of alloying elements can greatly affect the dehydrogenation properties of alloyed Y(BH₄)₃.