Contribution of d Orbitals in SiH SiH2, SiH3, and SiH4

Semi-empirical calculations have been carried out for SiHn (n=1, 2, 3, and 4) adopting the electron pair bond approximation using hybrid orbitals with d orbitals of Si determined by minimizing the energy of each ground state. The results are satisfactory as a whole for explaining the experimental data of these molecules. The contribution of d orbitals obtained is not very large, but it is important in discussing the energy levels and molecular structures of some low-lying electronic states. It is also shown that the maximum overlap method is not always adequate in determining hybrid orbitals including d orbitals.