(Heisenberg) exchange and electrostatic interactions between O2 molecules: An ab initio study

TLDR: In this article, the electrostatic and exchange interactions between two ground state 3Σ−g O2 molecules have been calculated ab initio by means of first order exchange perturbation theory, and the nonorthogonality problem has been handled in a second-quantized holeparticle formalism by a generalization of Wick's theorem.

Abstract: The electrostatic and exchange interactions between two ground state 3Σ−g O2 molecules have been calculated ab initio by means of first order exchange perturbation theory. The nonorthogonality problem has been handled in a second‐quantized hole‐particle formalism by a generalization of Wick’s theorem. The splitting between the spin states, S=0, 1, and 2, of the O2–O2 dimer is accurately represented by the Heisenberg Hamiltonian. By means of a spherical expansion for the orientational dependence and exponential functions for the distance dependence of the expansion coefficients, complete analytic potential surfaces have been evaluated, both for the spin‐independent term in the Heisenberg Hamiltonian ∼(ΔE) and for the exchange coupling parameter J. The strong anisotropy and distance dependence of J indicate that magnon–libron and magnon–phonon coupling in solid O2 are likely to be strong. A simple four‐electron model containing the O2 open shells only reproduces the structure dependence of J qualitatively, ...