The potential-energy surfaces (PES s) and electronic structures of neutral interstitial hydrogen in zinc-blende A1P and SiC are calculated and compared with those previously obtained at the same theoretical level in diamond, Si, and zinc-blende BN and BP. The calculations are done in a variety of clusters at the approximate ab initio Hartree-Fock level with the method of partial retention of diatomic differential overlap. The PES has three minima in each host: near the bond-centered {BC) site, and at the two inequivalent tetrahedral interstitial ( T) sites. At the BC site, H always forms a stronger bond with the least electronegative atom. The lowest in energy of the two T sites always is the one with the four least electronegative nearest neighbors. In AlP and SiC, the BC site is not the absolute minimum of the PES. Systematic trends in the properties of H with the ionic character of the host are apparent. The diffusion characteristics of H in the various hosts are discussed. The equilibrium structures of H and H+ are calculated. Our results show that p+ is (Mu*)+. The various transitions involving p+ (Mu*~p+, Mu~p+, or p+ -+Mu) observed in Si, Ge, GaAs, or SiC are consistent with our PES's.

The equilibrium structure, electronic properties and potential energy surfaces of interstitial oxygen (Oi) in c-C, Si, BP, AlP, c-SiC and c-BN are calculated in small and large molecular clusters. The theoretical level ranges from the 'approximate ab initio' Hartree-Fock method of partial retention of diatomic differential overlap to large-basis-set ab initio Hartree-Fock followed by second-order corrections for electron correlation (MP2). The equilibrium site is a puckered bridged bond in all hosts. In compound semiconductors, Oi has a larger degree of bonding with the most electronegative of the two host atoms (P, C or N) than with the least electronegative one and puckers in a direction that maximizes the overlap with its second-nearest neighbour. The dipole moment of the defect and the barrier for reorientation of Oi around and through the (111) axis are calculated. In order to estimate the relative stability of Oi in the various hosts, we determine the energies involved in inserting molecular O2 into the lattice and dissociating it into two isolated Ois. Finally, we calculate the barriers for migration of Oi between adjacent equilibrium sites. There are two such barriers in compound semiconductors. Whenever possible, we correlate the properties of Oi with various properties of the host, such as its and length and its ionic character, in order to gain predictive insight into the fundamental properties of interstitial oxygen in semiconductors.

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Potential energy surfaces and electronic structures of interstial oxygen (Oi) in cubic C, Si, AIP, SiC, and BN have been calculated. The equilibrium site is a bent-bridged bond. In compound semiconductors, Oi has a larger degree of bonding with the most electronegative of the host atoms (P, C, or N) than with the least electronegative one. In addition to the barrier for rotation of O, about the < 111 > axis, which does not involve breaking a bond, we calculated the barriers for migration between adjacent bond-centered sites. There are two such barriers in compound semiconductors. In order to estimate the relative stability of Oi in the various hosts, we calculated the energies involved in inserting O2 into the lattice and dissociating it into two isolated Oi's.