Pyrite type SiP2 is reinvestigated by first principles calculations on various levels of functionals including local density approximation, generalized gradient approximation, Becke-Lee-Yang-Parr hybrid functional, and the Hartree-Fock method. SiP2 is seen as a model compound with molecular [P-P] entities and [SiP6] octahedra. Structure and bonding are addressed by electronic structure calculations. Special attention is spent on P-P and Si-P bonds in terms of bond lengths and respective stretching modes from simulated Raman spectra. The electronic structure is analyzed in both direct and momentum space by the electron localization function and site projected density of states. The main goals of this work are to understand the nature of chemical bonding in SiP2 and to compare and contrast the different methods of calculation. (C) 2011 American Institute of Physics. [doi:10.1063/1.3633951]