The Unrestricted Hartree-Fock Theory of Chemical Reactions. III: Instability Conditions for Paramagnetic and Spin Density Wave States and Application to Internal Rotation of Ethylene

Open Access
Publisher Website
Google Scholar
Abstract
Instability conditions applicable to paramagnetic and spin density wave electronic configurations with a time reversal invariant set of spacial orbitals are derived. It is shown that there are four types of instability, the spin-unflip and spin-flip instabilities preserving or breaking time reversal invariance. The instability conditions are applied to internal rotation of ethylene. It is shown that the spin density wave state becomes spin-flip unstable in the region where it becomes of higher energy than the triplet paramegnetic state and the latter state which is initially spin-flip unstable becomes stable in the region. All solutions of the UHF equation for homopolar two-center two-electron system, including those with orbitals of torsional spin arrangement and of broken time reversal symmetry, are listed up and their properties are discussed. The stability-instability correlation between the paramagnetic and spin density wave solutions and the adiabatic potentials of the UHF solutions are discussed in relation to internal reaction of ethylene.

This publication has 2 references indexed in Scilit: