THEORETICAL-STUDIES OF MG(S-1, P-3) ATOM REACTION-MECHANISMS WITH HF, H2O, NH3, HCL, H2S, AND PH3 MOLECULES

The reaction mechanisms of Mg (1S and 3P) atom and XH molecules (X=F, OH, NH2, Cl, SH, and PH2) were studied by ab initio molecular orbital methods. A localized molecular orbital centroid analysis along the reaction coordinate shows that the (Mg(S))-S-1 atom insertion into the X-H bonds occurs through the pull-push mechanism. The activation barriers for the (Mg(S))-S-1 atom insertion are approximately the same values for each groups (X=F and Cl, OH and SH, and NH2 and PH2). For the (Mg(P))-P-3 atom reactions with above six compounds, the hydrogen abstraction (produces MgH and H) and/or the exchange reaction (produces MgX and H) were studied. Both reactions of (Mg(P))-P-3 atom are the same one with two-step mechanism. The first step is an electron transfer from a Mg atom into the X-H bonds, which corresponds the transition state. The activation barrier height of the reaction is explained by adiabatic electron affinity of the X-H bonds. The second step is the formation of the products (Mg-X+H or Mg-H+X), which is clarified by the difference of Mg-X and Mg-H bond energies.