Spin-flip, tensor equation-of-motion configuration interaction with a density-functional correction: A spin-complete method for exploring excited-state potential energy surfaces

2015 ◽  
Vol 143 (23) ◽  
pp. 234107 ◽  
Author(s):  
Xing Zhang ◽  
John M. Herbert
Keyword(s):  
Excited State ◽  
Potential Energy ◽  
Configuration Interaction ◽  
Potential Energy Surfaces ◽  
Density Functional ◽  
Equation Of Motion ◽  
Tensor Equation ◽  
Functional Correction ◽  
State Potential ◽  
Energy Surfaces

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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