Energetics of hydrogen in amorphous silicon: Anab initiostudy

Using ab initio density-functional calculations, we investigate the energetics of hydrogen in amorphous silicon. We compare a hydrogen atom at a silicon bond center site in $a$-Si to one in $c$-Si. In addition, we identify the energetics of the dominant traps for H in $a$-Si. The present calculations are used to elucidate many experiments and concepts regarding hydrogen in amorphous silicon including the role of H in equilibrium electronic defect formation.