Abstract: The geometrical structures of SiOM (M=Li, Be, B, Na, Mg, Al) complexes have been optimized by using Gaussian₉₄program, B3LYPmethod and the6-311+G( 2d)6d basis set.The calculated results show that Matom can attach to both the silicon atom and oxygen atom in the silicon monooxide molecule.All SiOMcomplexes except SiOAl have more than one stable structures.Furthermore, the most stable geometries of SiOM (M=Li, Be, Na, Mg) complexes are the bent structures, while SiOBand SiOAl complexes have nearly linear or linear structures in their most stable geometries.By the analysis of the Si-Oseparation, force constants of Si-Oand the natural bond orbital analysis, it has been shown that there are highly ionic fractions between the alkali atom and SiOin the most stable structures of the SiOLi and SiONa complexes.These structures, therefore, can be seen as ionic bondings.On the other hand, there are lowly ionic fractions between Matom and SiOin the geometries whose centers are silicon atoms ( i.e., SiOLi configuration Ⅱ, SiOBe configuration Ⅱ, SiOBconfiguration Ⅲ, SiOMg configuration Ⅱ).Thus, these structures can be seen as a kind of weak bonding interactions, not as ionic bondings.

Key words: DFT method, Structural property, SiOM complex