On the description of potential energy surfaces exhibiting conical intersections: a compact representation of the energies and derivative couplings and locally diabatic bases for the HOH and OHH portions of the 11 A-21 A seam of conical intersection in water

Abstract

The locus of the 1¹A′-2¹A′ seam of conical intersection for both HOH and OHH nuclear configurations in water is determined. Analytical expressions for the energies and derivative couplings in the vicinity of the conical intersections are presented. At each point of conical intersection a transformation to approximate diabatic states, based only on information about the derivative couplings, is defined. This transformation removes the preponderance of the derivative coupling near the conical intersection.