Hydrogen site occupation inYPd3withL12structure

Abstract

Hydrogen site occupation in a binary metal compound of YPd{sub 3} with L1{sub 2} structure is studied experimentally and theoretically. In contradiction to the semiempirical heat of the formation model, which predicts the interstitial site preferably occupied by hydrogen atoms in intermetallic compounds, the present neutron-diffraction study reveals that the hydrogen atoms occupy preferentially the characteristic interstitial site surrounded by six Pd atoms rather than the interstices surrounded by two Y and four Pd atoms. This result is confirmed by the first-principles calculations based on the local-density-functional theory. The difference in the electronic interactions between hydrogen and host atoms is shown to be largely responsible for the occupation of the specified interstitial sties by hydrogen in intermetallic hydride. {copyright} {ital 1997} {ital The American Physical Society}