  We discuss the possibility of a Kondo like effect associated with H in metals
resulting from the strong dependence of the H1s orbital radius on the
occupation number. We demonstrate that such a strong breathing property of the
orbital radius, which translates directly into a strong occupation dependent
hopping, results in the formation of local singlet-like bound states involving
one electron on H and one on the surrounding metal orbitals. We also show that
already at a mean field level an occupation dependent hopping integral leads to
a substantial potential energy correction on hydrogen, and that the failure of
LDA to incorporate this correction is probably responsible for the incorrect
prediction of a metallic ground state for the YH3 switchable mirror compounds.

Strongly Correlated Electrons