The structural and electronic properties of substitutional P and N impurities were studied by means of pseudopotential total-energy calculations. It was noted that substitutional P and N, in their neutral states, formed shallow acceptors. In the case of P, the symmetry was lowered from Td to C3v by Jahn-Teller distortion, and the hole was more localized on the P site. However, in the case of N the Jahn-Teller distortion was so small that the symmetry was approximately Td and the hole density was spread around nearby Se-atom sites. For N in the positive charge state, 2 minimum-energy configurations were predicted: a stable state with approximately Td symmetry, and a metastable state with C3v symmetry which was 0.3eV higher in energy than the stable one.

K.W.Kwak, R.D.King-Smith, D.Vanderbilt: Physical Review B, 1993, 48[24], 17827-34