scholarly journals Quantum dynamical study of the O(D1)+HCl reaction employing three electronic state potential energy surfaces

2008 ◽  
Vol 128 (1) ◽  
pp. 014308 ◽  
Author(s):  
Huan Yang ◽  
Ke-Li Han ◽  
Shinkoh Nanbu ◽  
Hiroki Nakamura ◽  
Gabriel G. Balint-Kurti ◽  
...  
Keyword(s):  
Potential Energy ◽  
Electronic State ◽  
Potential Energy Surfaces ◽  
Dynamical Study ◽  
Quantum Dynamical ◽  
State Potential ◽  
Energy Surfaces

Potential Energy Surfaces

1996 ◽  
Author(s):  
Tomas Baer ◽  
William L. Hase
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Electronic State ◽  
Diatomic Molecule ◽  
Potential Energy Surfaces ◽  
Energy Surface ◽  
Electronic States ◽  
Dissociation Energies ◽  
State Potential ◽  
Energy Surfaces

Properties of potential energy surfaces are integral to understanding the dynamics of unimolecular reactions. As discussed in chapter 2, the concept of a potential energy surface arises from the Born-Oppenheimer approximation, which separates electronic motion from vibrational/rotational motion. Potential energy surfaces are calculated by solving Eq. (2.3) in chapter 2 at fixed values for the nuclear coordinates R. Solving this equation gives electronic energies Eie(R) at the configuration R for the different electronic states of the molecule. Combining Eie(R) with the nuclear repulsive potential energy VNN(R) gives the potential energy surface Vi(R) for electronic state i (Hirst, 1985). Each state is identified by its spin angular momentum and orbital symmetry. Since the electronic density between nuclei is different for each electronic state, each state has its own equilibrium geometry, sets of vibrational frequencies, and bond dissociation energies. To illustrate this effect, vibrational frequencies for the ground singlet state (S0) and first excited singlet state (S1) of H2CO are compared in table 3.1. For a diatomic molecule, potential energy surfaces only depend on the internuclear separation, so that a potential energy curve results instead of a surface. Possible potential energy curves for a diatomic molecule are depicted in figure 3.1. Of particular interest in this figure are the different equilibrium bond lengths and dissociation energies for the different electronic states. The lowest potential curve is referred to as the ground electronic state potential. The primary focus of this chapter is the ground electronic state potential energy surface. In the last section potential energy surfaces are considered for excited electronic states. A unimolecular reactant molecule consisting of N atoms has a multidimensional potential energy surface which depends on 3N-6 independent coordinates. For the smallest nondiatomic reactant, a triatomic molecule, the potential energy surface is four-dimensional (three independent coordinates plus the energy). Since it is difficult, if not impossible, to visualize surfaces with more than three dimensions, methods are used to reduce the dimensionality of the problem in portraying surfaces. In a graphical representation of a surface the potential energy is depicted as a function of two coordinates with constraints placed on the remaining 3N-8 coordinates.

scholarly journals Diagonal Born–Oppenheimer corrections to the ground electronic state potential energy surfaces of ozone: improvement of ab initio vibrational band centers for the 16O3, 17O3 and 18O3 isotopologues

2020 ◽  
Vol 22 (42) ◽  
pp. 24257-24269 ◽  
Author(s):  
Attila Tajti ◽  
Péter G. Szalay ◽  
Roman Kochanov ◽  
Vladimir G. Tyuterev
Keyword(s):  
Potential Energy ◽  
Ab Initio ◽  
Electronic State ◽  
Potential Energy Surfaces ◽  
Vibrational Band ◽  
Ground Electronic State ◽  
Vibrational Levels ◽  
State Potential ◽  
Energy Surfaces

The accuracy of variationally calculated vibrational levels of ozone can be greatly improved by adding diagonal Born–Oppenheimer correction to the best available ab initio potential.

Resolving the Quadruple Bonding Conundrum in C2 Using Insights Derived from Excited State Potential Energy Surfaces: A Molecular Orbital Perspective

2019 ◽  
Author(s):  
Ishita Bhattacharjee ◽  
Debashree Ghosh ◽  
Ankan Paul
Keyword(s):  
Excited State ◽  
Potential Energy ◽  
Molecular Orbital ◽  
High Spin ◽  
Potential Energy Surfaces ◽  
Valence Bond ◽  
Deep Minimum ◽  
State Potential ◽  
Energy Surfaces ◽  
Mo Theory

The question of quadruple bonding in C<sub>2</sub> has emerged as a hot button issue, with opinions sharply divided between the practitioners of Valence Bond (VB) and Molecular Orbital (MO) theory. Here, we have systematically studied the Potential Energy Curves (PECs) of low lying high spin sigma states of C<sub>2</sub>, N<sub>2</sub> and Be<sub>2</sub> and HC≡CH using several MO based techniques such as CASSCF, RASSCF and MRCI. The analyses of the PECs for the<sup> 2S+1</sup>Σ<sub>g/u</sub> (with 2S+1=1,3,5,7,9) states of C<sub>2</sub> and comparisons with those of relevant dimers and the respective wavefunctions were conducted. We contend that unlike in the case of N<sub>2</sub> and HC≡CH, the presence of a deep minimum in the <sup>7</sup>Σ state of C<sub>2</sub> and CN<sup>+</sup> suggest a latent quadruple bonding nature in these two dimers. Hence, we have struck a reconciliatory note between the MO and VB approaches. The evidence provided by us can be experimentally verified, thus providing the window so that the narrative can move beyond theoretical conjectures.

Accuracy of Coupled Cluster Excited State Potential Energy Surfaces

2018 ◽  
Vol 14 (11) ◽  
pp. 5859-5869 ◽  
Author(s):  
Attila Tajti ◽  
John F. Stanton ◽  
Devin A. Matthews ◽  
Péter G. Szalay
Keyword(s):  
Excited State ◽  
Potential Energy ◽  
Potential Energy Surfaces ◽  
Coupled Cluster ◽  
State Potential ◽  
Energy Surfaces

scholarly journals Beyond the Coulson–Fischer point: characterizing single excitation CI and TDDFT for excited states in single bond dissociations

2019 ◽  
Vol 21 (39) ◽  
pp. 21761-21775 ◽  
Author(s):  
Diptarka Hait ◽  
Adam Rettig ◽  
Martin Head-Gordon
Keyword(s):  
Excited State ◽  
Potential Energy ◽  
Excited States ◽  
Potential Energy Surfaces ◽  
Single Bond ◽  
State Potential ◽  
Energy Surfaces ◽  
Single Bonds

HF/DFT orbitals spin-polarize when single bonds are stretched past the Coulson–Fischer point. We report unphysical features in the excited state potential energy surfaces predicted by CIS/TDDFT in this regime, and characterize their origin.

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