The electronic nonadiabatic coupling term: Can it be ignored in dynamic calculations?

Self Cite

In this article are considered the conical intersections ͑ci's͒ related to the N-H bond in the methylamine, CH 3 NH 2 , molecule. The novel feature that was revealed is that the two lowest states 1AЈ and 1AЉ are coupled by a line of cis located in HC-NHH plane-a line that is formed by moving a single hydrogen on that plane while fixing the ͑six͒ other atoms. The validity of this line was proven first by studying the singularities of the ͑angular͒ nonadiabatic coupling terms and then by revealing the degeneracy points formed by the two interacting adiabatic potential energy surfaces ͑PESs͒. A theoretical analysis indicated that the line has to be a finite closed line. We also calculated the Berry phase for a contour that surrounds this line and found it to be 3.127 rad, namely, a value reasonably close to . The existence of such lines of cis-instead of isolated cis ͑as exhibited by other n-atomic ͑n Ͼ 3͒ molecules such as HNCO or C 2 H 2 ͒-may enhance significantly the transition rate from an upper adiabatic state to a lower one. There are also numerical advantages in such situations, that is, if such a line is properly placed in that plane ͑like in the present case͒ the wave-packet treatment of the nuclei can be carried out employing a single diabatic PES instead of having to consider two coupled PESs.

Section: Discussionmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] In the present article we consider a much larger system, the methylamine molecule, CH 3 NH 2 , consisting of seven atoms. The structure of the molecule is given in Fig.…”

Section: Introductionmentioning

confidence: 99%

An intraline of conical intersections for methylamine

Levi

Halász

Vibók

et al. 2008

Self Cite

“…An active area of research is finding ways to compute derivative couplings more easily. 10 A second approach toward diabatization is to avoid calculating derivative coupling elements explicitly, but rather minimize them implicitly by designing diabatic states with intuitively desirable mathematical characteristics. Popular examples of these approaches are block diagonalization 11,12 and the fourfold way [13][14][15][16][17] ͑see also Ref.…”

Section: A Diabatic Surfacesmentioning

confidence: 99%

Constructing diabatic states from adiabatic states: Extending generalized Mulliken–Hush to multiple charge centers with Boys localization

Subotnik

Yeganeh

Cave

et al. 2008

241

307

This article shows that, although Boys localization is usually applied to single-electron orbitals, the Boys method itself can be applied to many electron molecular states. For the two-state charge-transfer problem, we show analytically that Boys localization yields the same charge-localized diabatic states as those found by generalized Mulliken-Hush theory. We suggest that for future work in electron transfer, where systems have more than two charge centers, one may benefit by using a variant of Boys localization to construct diabatic potential energy surfaces and extract electronic coupling matrix elements. We discuss two chemical examples of Boys localization and propose a generalization of the Boys algorithm for creating diabatic states with localized spin density that should be useful for Dexter triplet-triplet energy transfer.

“…͑5͒ and ͑6͒ exactly do not usually exist, 17 one can select diabatic states where the derivative couplings above are minimized. 6,7 With this definition, diabatic states are coupled together only very weakly through the nuclear derivative, but they can now be coupled together moderately through the electronic Hamiltonian ͗⌶ i ͑r ; R͉͒H el ͑r ; R͉͒⌶ j ͑r ; R͒͘, resulting in the so-called diabatic couplings or H AB 's that appear in nonadiabatic electron transfer theory.…”

Section: A the Historical Motivation For Diabatic Statesmentioning

confidence: 99%

“…[1][2][3] Within the context of nonadiabatic quantum dynamics, one historical definition is that diabatic states are the many-electron states with zero ͑or minimal͒ nuclear derivative couplings. [4][5][6][7] Within the context of a system that can undergo electron or energy transfer in a condensed environment, another definition is that the diabatic states are the initial and final states of the system before or after the transfer process. 8,9 Many other definitions exist.…”

Section: Introduction To Diabatic Statesmentioning

confidence: 99%

The initial and final states of electron and energy transfer processes: Diabatization as motivated by system-solvent interactions

Subotnik¹,

Cave²,

Steele³

et al. 2009

139

192

For a system which undergoes electron or energy transfer in a polar solvent, we define the diabatic states to be the initial and final states of the system, before and after the nonequilibrium transfer process. We consider two models for the system-solvent interactions: A solvent which is linearly polarized in space and a solvent which responds linearly to the system. From these models, we derive two new schemes for obtaining diabatic states from ab initio calculations of the isolated system in the absence of solvent. These algorithms resemble standard approaches for orbital localization, namely, the Boys and Edmiston-Ruedenberg ͑ER͒ formalisms. We show that Boys localization is appropriate for describing electron transfer ͓Subotnik et al., J. Chem. Phys. 129, 244101 ͑2008͔͒ while ER describes both electron and energy transfer. Neither the Boys nor the ER methods require definitions of donor or acceptor fragments and both are computationally inexpensive. We investigate one chemical example, the case of oligomethylphenyl-3, and we provide attachment/detachment plots whereby the ER diabatic states are seen to have localized electron-hole pairs.