The potential energy surface of [H,N,Si,O] has been generated using the G3B3 methods. Transition states and dissociations have been calculated at the same level. Calculations have also been carried out using ab initio methods at the MP2/6-311 + G(d,p) level and the results of the DFT methods (B3LYP/6-31G(d) and G3B3) compared; good agreement between these methodologies was observed, particularly for the optimized geometries and relative energies. On this surface, many intersystem crossings between the singlets and the triplets occur, and the geometries at these crossing points have also been estimated. Finally the reaction coordinates of neutral-neutral reactions of the fragments leading to the stable isomers have been mapped.