Stability of elastically deformed massive and nanometer-sized Pd hydrides

Molecular dynamics simulations have been employed to investigate the effect of tensile and compressive uniaxial elastic deformations on the heat of formation of massive and nanometer-sized PdH(0.6) beta phases. The numerical findings indicate that bulk PdH(0.6) beta phases are generally more stable than PdH(0.6) beta phase nanowires, the heat of formation increasing as the system size decreases. Reducing the system size also determines a softening of both Pd and PdH(0.6) beta phase crystalline lattices, pointed out by a linear decrease of the Young moduli with the reciprocal of the system size. Finally, it is shown that the heat of formation of strained PdH(0.6) beta phases starting from strained Pd lattices is significantly affected by uniaxial stresses. In particular, the heat of formation of PdH(0.6) beta phases increases as the Pd systems are elongated, whereas it decreases as the PdH(0.6) beta phase lattice is compressed.