氧化锰团簇中锰与氧配位的DFT计算

A DFT Study on the Coordination Nature in Manganese Oxide Cluster

利用密度泛函方法，研究了过渡金属Mn与O的配位性质。对可能的配位方式进行了结构优化；对它们的稳定性、分子轨道组成及能级结构进行了分析。结果表明，Mn的3d、4s、4p轨道能以不同的组合方式与O的2p轨道形成良好的空间重叠，因此锰和氧能以灵活的配住方式形成各种饱和或不饱和的稳定结构。其中最稳定的配位方式是八面体六配位、四面体四配位和平面四配位。

Silica supportec manganese-tungsten is among the best catalysts for oxidative coupling of methane. Experiment study suggests that manganese exists in the form of oxide clustersover the catalyst surface and play a key role for the activation of molecular oxygen. Thecalculation method is based on density functional theory, and an the calculation is carried outat the generalized gradient approximation level. Analysis of the total bonding energy, Mn-Obond lengths and the atom charges shows that the most stable structures are sir coordinatedoctahedral structure and four coordinated tetrahedral or planar structure. The energy levels ofthese model give two bands, contributed from the oxygen 2s orbitals, manganese 3d, 4s and oxygen 2p orbitals respectively. Compositions of the molecular orbitals reveal that the valenceorbitals of manganese can combine in different ways to make maximal overlap with the 2porbitals of oxygen, and so the unsaturately coordinated manganese oxides can combine and activate oxygen easily.