Development and application of ab initio calculations. I. Projected frequencies. II. Organic and inorganic reactive systems.

摘要

An improved method for calculating projected frequencies along reaction paths has been developed. This method uses the Hessian to take a Newton-Raphson step to improve the convergence of the reaction path following. The {dollar}rm Ssb{lcub}N{rcub}2{dollar} reaction of {dollar}rm Clsp-{dollar} with {dollar}rm CHsb3Cl{dollar} computed at the HF/6-31G* level of theory has been used as a test case.; Ab inito electronic structures methods were used to calculate structures and energetics of a number of organic and inorganic reactive systems. A study of the vinyl {dollar}rm Ssb{lcub}N{rcub}2{dollar} reaction confirmed that {dollar}sigma{dollar}-attack is favored for vinyl halides but found the traditional {dollar}pi{dollar}-attack is favored for substituted vinyl halides. The oxidation of sulfides, sulfoxides, amines and phosphines by dioxiranes, and carbonyl oxides, has been investigated at MP2, MP4, QCISD(T) and B3LYP levels of theory using 6-31G* basis set. The geometries and heats of formation of 48 isomers of {dollar}{lcub}rm SiH{rcub}sb{lcub}m{rcub}{lcub}rm PH{rcub}sb{lcub}n{rcub} 0le m + n le 5, {lcub}rm SiH{rcub}sb{lcub}m{rcub}{lcub}rm PH{rcub}sb{lcub}n{rcub}{lcub}rm SiH{rcub}sb{lcub}o{rcub} 0 le m + n + o le 7{dollar} and {dollar}rm (SiHsb3)sb3P{dollar} have been computed at the G2 level of theory. Two empirical schemes have been constructed to fit the atomization energies. Transition structures and barrier heights for the {dollar}{lcub}rm BH{rcub}sb{lcub}m{rcub}{lcub}rm Cl{rcub}sb{lcub}n{rcub}{dollar} system have been characterized at the G2 level of theory. The {dollar}{lcub}rm BH{rcub}sb{lcub}3-n{rcub}{lcub}rm Cl{rcub}sb{lcub}n{rcub} + {lcub}rm H to BH{rcub}sb{lcub}2-n{rcub}{lcub}rm Cl{rcub}sb{lcub}n{rcub} + {lcub}rm Hsb2{rcub}{dollar} reaction does not occur by abstraction, but by addition-elimination via a tetra-coordinate intermediate and a highly distorted, non-least motion transition state. The heats of formations of various potential intermediates in the CVD production of TiN films have been studied using a variant of the G2 level of theory. The structures of {dollar}{lcub}rm TiCl{rcub}sb{lcub}m{rcub}{lcub}rm (NHsb2){rcub}sb{lcub}n{rcub}, 0 le {lcub}rm m + n le 4{rcub},{dollar} TiCl{dollar}sb{lcub}m{rcub}{lcub}rm (NHsb2){rcub}sb{lcub}n{rcub}{lcub}rm NH{rcub}, 0 le rm m + n le 2,{dollar} and TiCl{dollar}sb{lcub}m{rcub}{lcub}rm (NHsb2){rcub}sb{lcub}n{rcub}{lcub}rm N{rcub}, 0 le rm m + n le 1,{dollar} were optimized at B3LYP level of theory with the Wachters-Hay basis set for Ti and the 6-311G(d) basis set for H, N and Cl.