The energy gain in Si crystal systems as a function of the distance between a hydrogen (H) atom and a boron (B) or phosphorus (P) dopant atom was investigated using first principles calculation. The giving and taking of an electron between an H atom and a B or P dopant atom was found to respectively result in a gain of about 0.97 eV or 0.68 eV, even when the atoms were fully separated and had no direct interactions. An ionized H atom in B-doped Si crystals always was found to exist at the bond-center site whether it was located near a B atoms or not. H atoms in P-doped Si crystals were found to be stable at tetrahedral sites except in the vicinity of a P atom. In this vicinity, H atoms prefer to go into an anti-bonding site. In the models used to obtain these results, the electronic states in the energy gaps were totally annihilated if an H atom was within the B-or P-atom vicinity but remained if it was located slightly apart from them. However, there were far fewer gap states in models with a B atom than in those with a P atom. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.098204jes] All rights reserved.