DISTINCT QUANTUM BEHAVIOR OF HYDROGEN AND MUONIUM IN CRYSTALLINE SILICON

Feynman path-integral Monte Carlo simulations have been performed to s tudy finite-temperature properties of isolated hydrogenlike impurities in crystalline silicon. The Si-H interaction was modeled following th e results of earlier pseudopotential-density-functional calculations f or this system. Hydrogen is found to be stable at the bond-center (BC) site. However, the same potential model predicts that muonium is high ly delocalized in the interstitial region. This mass-induced effect is shown to be a consequence of the uncertainty principle, which prevent s localization of muonium at the BC site due to an increase of its kin etic energy.