Read the papers of Chadi and Cohen (Phys. Rev. B 8, 5747 (1973)), and after that the paper of Mokhirst and Pack (Phys. Rev. B 13, 5188 (1976))
Read the papers of Chadi and Cohen (Phys. Rev. B 8, 5747 (1973)), and after that the paper of Mokhirst and Pack (Phys. Rev. B 13, 5188 (1976))