First-principle study of hydrogen stability within TiCo3

Structural and electronic changes due to hydrogen uptake within TiCo3 are examined ab initio within DFT using both pseudo-potential and all electron calculations. For the monohydride two starting hypotheses for H position, at cube center and cube-edge middle, were considered and analyzed: the system stabilizes with a cubic structure which undergoes a tetragonal distortion when H is at edge middle. Detailed analyses of the site projected density of states and of the electron count conclude to meaningful changes of the electronic structure when H is inserted, especially for the weakening of the chemical bonding in the tetragonally distorted lattice. The results could explain the brittleness characterizing the hydrided 1:3 alloy systems.

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