SiOM(M=Li,Be,B,Na,Mg,Al)分子结构的DFT研究

利用Gaussian-94计算程序,B3LYP方法,6-311+G(2d)6d基组,对SiOM(M=Li,Be,B,Na,Mg,Al)诸体系的几何结构进行优化.结果表明,M既可与SiO中的Si键合,也可与O键合.第一和第二主族的SiOM体系以折线形构型为最稳定构型,而第三主族则以近直线形或直线形构型为最稳定构型.从Si-O间键长R_SiO、力常数f_SiO及自然键轨道分析可知,第一主族的SiOLi和SiONa的最稳定构型中SiO-M间的离子键成分较大,可近似看作离子键;而对SiOLi,SiOBe,SiOB和SiOMg体系的以Si为中心的构型,M-SiO间的离子键成分很小,不能看作离子键,可认为M与SiO之间存在着弱相互作用

Density Functional Study on the Structures of the SiOM (M=Li, Be, B, Na, Mg, Al) Complexes

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.