Geometry Optimization in the Computation of Barriers to Internal Rotation

Abstract

A minimum basis set of STO's has been used to compute wavefunctions for eclipsed and staggered C₂H₆ and for several forms of H₂O₂. For each form all the exponents and free geometric parameters have been varied to obtain the minimum energy. It has been found that the geometry variation has little effect on the computed barrier in C₂H₆, and the results agree well with experiment. For H₂O₂, it has been found that the minimum geometry changes substantially between the cis and trans forms, and the results agree poorly with experiment. However, the geometry variation does produce better agreement for the barrier than similar calculations with fixed geometry.