Steric and electric field driven distortions in aromatic molecules: spontaneous and non-spontaneous symmetry breaking.

نویسندگان

  • Kalishankar Bhattacharyya
  • Ammu Surendran
  • Chandra Chowdhury
  • Ayan Datta
چکیده

The structures of molecules form the cornerstone of our chemical knowledge. Lowering of symmetry in closed-shell molecules is often attributed to the Pseudo Jahn-Teller (PJT) distortions wherein non-adiabatic coupling (NAC) between the ground state and excited states creates vibrational instability along specific normal modes. Nevertheless, other factors like steric interactions are also well known in the literature to induce structural distortions. In this article, we consider two specific cases of molecular distortions - the first one being spontaneous for contorted polyaromatic hydrocarbons (c-PAH) where non-bonded repulsions between the two pairs of syn H-atoms in tribenzopyrene, TBP (1), can enforce either a C2v → C2 or C2v → Cs distortion. PJT-effects account for the correct preference of the Cs structure over C2 (by 4.6 kcal mol-1). The second case (non-spontaneous symmetry breaking) is that of benzene (2) and coronene (3) which upon application of sufficiently strong static external electric field develop vibrational instability along q(a2u) to cause D6h → C6v and D6h → C2 distortions for 2 and 3 respectively. An external electric field (FZ) was applied parallel to the aromatic ring of 2-3 for investigation of non-spontaneous symmetry breaking. Such electric field induced structural distortion is understood on the basis of excess charge accumulation of the planar rings which is circumvented by symmetry lowering. PJT effects seem to have significant consequences for identification of global minima amongst several local minimal molecular structures.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

A Computational Study to Find the Vibrational Modes Connected with Specific Molecular Structures of Calculated Compound

The purpose of this research is to provide a deeper understanding of the planar high- symmetry configuration instability. In the ideal case, the distortion corresponds to the movements of nuclei along normal modes that belong to non-totally symmetric irreps of the high symmertry (HS) point group of molecule. The analysis of the structural distortion from the HS nuclear arrangements of the JT ac...

متن کامل

نظریه میدان ناجابه‌جایی و پارامترهای نقض لورنتس در QED

Non-commutative field theory as a theory including the Lorentz violation can be constructed in two different ways. In the first method, the non-commutative fields are the same as the ordinary ones while the gauge group is restricted to U(n). For example, the symmetry group of standard model in non-commutative space is U(3)×(2)×U(1) which can be reduced to SU(3)×SU(2)×U(1) by two appropriate spo...

متن کامل

Spontaneous Emission Spectrum from a Driven Three-Level Atom in a Double-Band Photonic Crystal

Abstract The spontaneous emission spectrum from a driven three-level atom placed inside a double-band photonic crystal has been investigated. We use the model which assumes the upper levels of the atomic transition are coupled via a classical driving field. The transition from one of the upper levels to lower level couples to the modes of the modified reservoir, and the transition from the oth...

متن کامل

Spontaneous Symmetry Breaking in a Non-Conserving Two-Species Driven Model

A two species particle model on an open chain with dynamics which is non-conserving in the bulk is introduced. The dynamical rules which define the model obey a symmetry between the two species. The model exhibits a rich behavior which includes spontaneous symmetry breaking and localized shocks. The phase diagram in several regions of parameter space is calculated within mean-field approximatio...

متن کامل

Spontaneous symmetry breaking in a quadratically driven nonlinear photonic lattice

We investigate the occurrence of a phase transition, characterized by the spontaneous breaking of a discrete symmetry, in a driven-dissipative Bose-Hubbard lattice in the presence of two-photon coherent driving. The driving term does not lift the original U(1) symmetry completely and a discrete Z2 symmetry is left. When driving the bottom of the Bose-Hubbard band, a mean-field analysis of the s...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:
  • Physical chemistry chemical physics : PCCP

دوره 18 45  شماره 

صفحات  -

تاریخ انتشار 2016