Multireference CI Study of Excitation Energies and Potential Energy Surfaces of CH3F†

2004 ◽  
Vol 108 (15) ◽  
pp. 3111-3118 ◽  
Author(s):  
Glauco F. Bauerfeldt ◽  
Hans Lischka
Keyword(s):  
Potential Energy ◽  
Potential Energy Surfaces ◽  
Excitation Energies ◽  
Energy Surfaces

scholarly journals Accuracy of Spin-Component Scaled ADC(2) Excitation Energies and Potential Energy Surfaces

2019 ◽  
Author(s):  
Attila Tajti ◽  
Levente Tulipan ◽  
Péter Szalay
Keyword(s):  
Potential Energy ◽  
Excited States ◽  
Canonical Form ◽  
Potential Energy Surfaces ◽  
Second Order ◽  
Spin Component ◽  
Excitation Energies ◽  
Order Algebraic ◽  
Energy Surfaces

In a recent paper of this Journal (Tajti and Szalay, JCTC 2019, 15, 5523) we have shown that failures of the CC2 method to describe Rydberg excited states, as well as potential energy surfaces of certain valence excited states can be cured by spin-component scaled (SCS) versions SCS-CC2 and SOS-CC2 by a large extent. In this paper, the related and popular Second Order Algebraic Diagrammatic Construction (ADC(2)) method and its SCS variants are inspected with the previously established methodology. The results reflect the similarity of the CC2 and ADC(2) models, showing identical problems in the case of the canonical form and the same improvement when spin-component-scaling is applied.

A CNDO/2 Calculation on the Reaction of Ground State Oxygen Atoms with Olefins

1974 ◽  
Vol 52 (2) ◽  
pp. 287-290 ◽  
Author(s):  
Seiichiro Koda
Keyword(s):  
Potential Energy ◽  
Ground State ◽  
Potential Energy Surfaces ◽  
Reaction Rate ◽  
Reaction Intermediates ◽  
Excitation Energies ◽  
Reaction Rate Constants ◽  
Molecular Orbital Study ◽  
Energy Surfaces ◽  
Oxygen Atoms

A molecular orbital study within the framework of the CNDO/2 method has been made of the reactions of ground state oxygen atoms with olefins. Calculated excitation energies confirm the existence of a certain correlation between those and the logarithm of the reaction rate constants. The location of minima in the simplified potential energy surfaces computed appear to correspond to the reaction intermediates suggested previously.

scholarly journals Accuracy of Spin-Component Scaled ADC(2) Excitation Energies and Potential Energy Surfaces

2019 ◽  
Author(s):  
Attila Tajti ◽  
Levente Tulipan ◽  
Péter Szalay
Keyword(s):  
Potential Energy ◽  
Excited States ◽  
Canonical Form ◽  
Potential Energy Surfaces ◽  
Second Order ◽  
Spin Component ◽  
Excitation Energies ◽  
Order Algebraic ◽  
Energy Surfaces

In a recent paper of this Journal (Tajti and Szalay, JCTC 2019, 15, 5523) we have shown that failures of the CC2 method to describe Rydberg excited states, as well as potential energy surfaces of certain valence excited states can be cured by spin-component scaled (SCS) versions SCS-CC2 and SOS-CC2 by a large extent. In this paper, the related and popular Second Order Algebraic Diagrammatic Construction (ADC(2)) method and its SCS variants are inspected with the previously established methodology. The results reflect the similarity of the CC2 and ADC(2) models, showing identical problems in the case of the canonical form and the same improvement when spin-component-scaling is applied.

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.

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