Interstitial muons and hydrogen in crystalline silicon

We have calculated self-consistent total energy surfaces for H+, H° and H2 present interstitially in crystalline Si. We conclude molecular hydrogen is the stable form consistent with the lack of observed electrical and optical activity. Both H+ and H° have complex surfaces, with some features sensitive to lattice distortion. The local minima are too small to give localised states when zero-point energy is included. We discuss our results in relation to earlier theories and to experiments on “normal” and “anomalous” muonium [μ+e-].