Comparative energy derivative analyses of the HBO–BOH and AlOH–HAlO potential energy hypersurfaces

A study of first and second derivatives of the orbital, electronic, nuclear, and total energies for closed-shell self-consistent-field (SCF) wave functions has been applied to the ground state HBO–BOH and AlOH–HAlO potential energy hypersurfaces. At the stationary points, these energy derivative quantities are uniquely transformed from the Cartesian to the normal coordinate system. Using the four equilibrium and four transition state structures on the two potential energy hypersurfaces, it is demonstrated that the energy derivative method may be used as a powerful quantitative model in understanding and interpreting various chemical phenomena including structures and reactivities. Specifically, the inversion (bending through linear geometry) motions for the bent BOH and AlOH molecules are found to be electronically favorable processes. The isomerization reaction between the linear HBO and bent BOH is seen to be electronically unfavorable, whereas the corresponding reaction between the bent AlOH and linear HAlO is observed to be an electronically favorable process.