We present a study of the non-adiabatic coupling terms (NACTs) and the corresponding diabatic potentials for the reactive H2 + F system in the entrance channel. The study reveals two conical intersections (ci): (I) A Jahn-Teller (1, 2) ci, located at a point on the collinear HHF axis close to the minimum energy path; (II) A Renner-Teller line of (2, 3) cis, along the collinear HHF axis. To form the diabatic potentials we consider only the two lower adiabatic potentials and the quantized Born-Oppenheimer mixing angles that guarantee single-valued diabatic potentials. © 2011 Elsevier B.V. All rights reserved.

DEBASIS MUKHOPADHYAY

Chemistry

A DAS

S ADHIKARI

M BAER

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Chemical Physics Letters

While a wealth of studies exist on the potential energy surface (PES) for the F + H2 reaction, exploration of the effect of conical intersections (CIs on the corresponding adiabatic PES has only been initiated. In this respect, a recent emphasis on the specific role of the Jahn-Teller (JT) CI between the two lowest states has shown that the adiabatic-to-diabatic transformation (ADT) angle (mixing angle), γ12, between these two states deviates largely from its quantized value of π for configuration spaces with F close to the H-H system. Hence, investigating the effect of the other CIs present, involving the higher states, on the reactive channel is necessary. In this article, we report for the first time the collinear (2, 3), (3, 4) and (4, 5) JT CIs in this system and also reveal their major effects on γ12, which is instrumental in the diabatization of the PES for the title reaction system. © 2012 Elsevier B.V. All rights reserved.

Chemical Physics

Jahn-Teller intersections involving excited states of the F + H2 system: Identification and influence on the reaction system

The present study concentrates on a situation where a Renner-Teller (RT) system is entangled with Jahn-Teller (JT) conical intersections. Studies of this type were performed in the past for contours that surround the RT seam located along the collinear axis see, for instance, G. J. Halász, Á. Vibók, R. Baer, and M. Baer, J. Chem. Phys. 125, 094102 (2006). The present study is characterized by planar contours that intersect the collinear axis, thus, forming a unique type of RT-non-adiabatic coupling terms (NACT) expressed in terms of Dirac-δ functions. Consequently, to calculate the required adiabatic-to-diabatic (mixing) angles, a new approach is developed. During this study we revealed the existence of a novel molecular parameter, η, which yields the coupling between the RT and the JT NACTs. This parameter was found to be a pure number η = 22/π (and therefore independent of any particular molecular system) and is designated as Renner-Jahn coupling parameter. The present study also reveals an unexpected result of the following kind: It is well known that each (complete) group of states, responsible for either the JT-effect or the RT-effect, forms a Hilbert space of its own. However, the entanglement between these two effects forms a third effect, namely, the RT/JT effect and the states that take part in it form a different Hilbert space. © 2013 American Institute of Physics.

Fulltext

Journal of Chemical Physics

A tri-atomic Renner-Teller system entangled with Jahn-Teller conical intersections

We follow a suggestion by Lipoff and Herschbach Mol. Phys. 108, 1133 (2010)10.1080/00268971003662912 and compare dressed and bare adiabatic potentials to get insight regarding the low-energy dynamics (e.g., cold reaction) taking place in molecular systems. In this particular case, we are interested to study the effect of conical intersections (ci) on the interacting atoms. For this purpose, we consider vibrational dressed adiabatic and vibrational dressed diabatic potentials in the entrance channel of reactive systems. According to our study, the most one should expect, in case of F H 2, is a mild effect of the (1, 2) ci on its reactiveexchange process-an outcome also supported by experiment. This happens although the corresponding dressed and bare potential barriers (and the corresponding van der Waals potential wells) differ significantly from each other. © 2012 American Institute of Physics.

Dressed adiabatic and diabatic potentials to study conical intersections for F + H 2

The tetra-atomic C2 H2+ cation is known to form Renner-Teller-type intersections along its collinear axis. Not too long ago, we studied the nonadiabatic coupling terms (NACTs) of this molecule [G. J. Halász, J. Chem. Phys. 126, 154309 (2007)] and revealed two kinds of intersections. (i) By employing one of the hydrogens as a test particle, we revealed the fact that indeed the corresponding (angular) NACTs produce topological (Berry) phases that are equal to 2π , which is a result anticipated in the case of Renner-Teller intersections. (ii) However, to our big surprise, repeating this study when one of the atoms (in this case a hydrogen) is shifted from the collinear arrangement yields for the corresponding topological phase a value that equals π (and not 2π ). In other words, shifting (even slightly) one of the atoms from the collinear arrangement causes the intersection to change its character and become a Jahn-Teller intersection. This somewhat unexpected novel result was later further analyzed and confirmed by other groups [e.g., T. Vertesi and R. Englman, J. Phys. B 41, 025102 (2008)]. The present article is devoted to another tetra-atomic molecule, namely, the H2 CN molecule, which just like the C2 H2+ ion, is characterized by Renner-Teller intersections along its collinear axis. Indeed, we revealed the existence of Renner-Teller intersections along the collinear axis, but in contrast to the C2 H2+ case a shift of one atom from the collinear arrangement did not form Jahn-Teller intersections. What we found instead is that the noncollinear molecule was not affected by the shift and kept its Renner-Teller character. Another issue treated in this article is the extension of (the two-state) Berry (topological) phase to situations with numerous strongly interacting states. So far the relevance of the Berry phase was tested for systems characterized by two isolated interacting states, although it is defined for any number of interacting states [M. V. Berry, Proc. R. Soc. London, Ser. A 392, 45 (1984)]. We intend to show how to overcome this limitation and get a valid, fully justified definition of a Berry phase for an isolated system of any number of interacting states (as is expected). © 2010 American Institute of Physics.

Renner-Teller intersections along the collinear axes of polyatomic molecules: H2 CN as a case study

The Journal of Physical Chemistry A

Proton-Coupled Electron Transfer versus Hydrogen Atom Transfer: Generation of Charge-Localized Diabatic States

The Journal of Chemical Physics

Interaction between LiH molecule and Li atom from state-of-the-art electronic structure calculations

Journal of Physics B: Atomic, Molecular and Optical Physics

Diabatic electronic states from many-body perturbation theory

Molecular Symmetry Properties of Conical Intersections and Nonadiabatic Coupling Terms: Theory and Quantum Chemical Demonstration for Cyclopenta-2,4-dienimine (C5H4NH)†

Journal	Chemical Physics Letters
Publisher	-
ISSN	0009-2614
Open Access	No