First-principles self-consistent total energy calculations for various configurations of atomic
and diatomic hydrogen inside fcc palladium have been carried out to clarify some of the
solid state aspects of the physics of dense hydrogen in metals. We find that the stability of
the system is controlled by the relative position of the hydrogen-induced antibonding level
with respect to the Fermi energy. Diatomic H 2 in crystalline palladium is shown to have but
metastable local minima whose internuclear separation are yet larger than that of the …