Unanticipated confluences of seams of conical intersection: Reinvestigating intersecting potential-energy surfaces using new tools. I. C(3P)+H2

Abstract

A new ab initio based global HOOH(13A″) potential energy surface for the O(3P) + H2O(X1A1) ↔ OH(X2Π) + OH(X2Π) reaction J. Chem. Phys. 138, 194304 (2013); 10.1063/1.4804418New ab initio coupled potential energy surfaces for the Br(2 P 3/2, 2 P 1/2) + H2 reaction Recently a quite unexpected situation has been found in which two distinct seams of conical intersection originating from the same two states-one the accidental intersection of two states of different symmetries and one the accidental intersection of two states of the same symmetryintersect. These confluences can now be systematically identified using an algorithm that relies solely on information obtained from the symmetry-allowed seam. It is necessary to ask whether, in the absense of such an algorithm, these confluences have been overlooked in the past. In this work the well studied 1 3 AЉ -2 3 AЉ seam of conical intersection in C( 3 P) -H 2 is reinvestigated using the above noted algorithm with surprising results.

Conical Intersections: The New Conventional Wisdom

“…It had been shown that in some triatomic molecules, − all of which had C 2 v or higher symmetry, an intersection or confluence of a symmetry-allowed seam of conical intersection and a seam of conical intersection of two states of the same-symmetry (a same-symmetry seam) exists . These intersections of intersections could be anticipated using the cross product of the two vectors that define the g − h plane. , Very recently we uncovered an interesting extension of this occurrence. , As noted previously in the tetra-atomic molecule HNCO, the ground 1 A‘ state and excited 1 A‘ ‘ state are connected by a symmetry-allowed seam of conical intersection for planar C s geometries. For nonplanar geometries a seam of conical intersection of two states of the same symmetry also exists.…”

Geometric Phase Effects in Chemical Reaction Dynamics and Molecular Spectra

“…It may consist of several branches and/or loops. Specialized electronic structure techniques are often required to accurately map out the shape of this one-dimensional subspace. , Fortunately, the minimum energy pathway around each of the linear conical intersections in HO 2 exhibits a barrier of about 0.42 eV relative to the asymptotic H + O 2 potential well . Thus, for total scattering energies below 0.42 eV, the nuclear motion wave function will not have appreciable amplitude along the entire minimum energy pathway around the linear conical intersections, and the effects of the geometric phase associated with these intersections can be ignored.…”

Symmetry Friend or Foe: Confluences of Conical Intersection Seams in Tetra-Atomic Molecules

“…Recently, it was shown that this is not always the case in triatomic molecules. − In some triatomic molecules, all of which had C 2 v or higher symmetry, an intersection or confluence of a symmetry-allowed seam of conical intersection, and a seam of conical intersection of two states of the same-symmetry (a same-symmetry seam) was found. We showed how these confluences could be anticipated using the cross product of the two vectors that define the g−h plane. , Subsequently, intersections of three symmetry equivalent, symmetry-allowed seams, with one symmetry-required seam were found in X 3 molecules. , …”