Analytic gradients, geometry optimization and excited state potential energy surfaces from the particle-particle random phase approximation

2015 ◽  
Vol 17 (2) ◽  
pp. 1025-1038 ◽  
Author(s):  
Du Zhang ◽  
Degao Peng ◽  
Peng Zhang ◽  
Weitao Yang
Keyword(s):  
Excited States ◽  
Potential Energy Surfaces ◽  
Random Phase Approximation ◽  
Theoretical Study ◽  
Random Phase ◽  
Geometry Optimization ◽  
Photochemical Reactions ◽  
Energy Gradient ◽  
State Potential ◽  
Energy Surfaces

The energy gradient for electronic excited states is of immense interest not only for spectroscopy but also for the theoretical study of photochemical reactions.

Excited State Tracking During the Relaxation of Coordination Compounds

2018 ◽  
Author(s):  
Juan Sanz García ◽  
Martial Boggio-Pasqua ◽  
Ilaria Ciofini ◽  
Marco Campetella
Keyword(s):  
Excited State ◽  
Excited States ◽  
Potential Energy Surfaces ◽  
Photochemical Reactions ◽  
Complex Nature ◽  
Electronic Excited States ◽  
Ruthenium Nitrosyl ◽  
State Tracking ◽  
Energy Surfaces ◽  
Electronic Wavefunction

<div>The ability to locate minima on electronic excited states (ESs) potential energy surfaces (PESs) both in the case of bright and dark states is crucial for a full understanding of photochemical reactions. This task has become a standard practice for small- to medium-sized organic chromophores thanks to the constant developments in the field of computational photochemistry. However, this remains a very challenging effort when it comes to the optimization of ESs of transition metal complexes (TMCs), not only due to the presence of several electronic excited states close in energy, but also due to the complex nature of the excited states involved. In this article, we present a simple yet powerful method to follow an excited state of interest during a structural optimization in the case of TMC, based on the use of a compact hole-particle representation of the electronic transition, namely the natural transition orbitals (NTOs). State tracking using NTOs is unambiguously accomplished by computing the mono-electronic wavefunction overlap between consecutive steps of the optimization. Here, we demonstrate that this simple but robust procedure works not only in the case of the cytosine but also in the case of the ES optimization of a ruthenium-nitrosyl complex which is very problematic with standard approaches.</div>

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.

Theoretical study of the PSi2 radical

1996 ◽  
Vol 74 (12) ◽  
pp. 2476-2480 ◽  
Author(s):  
Jose M. Elorza ◽  
Jesus M. Ugalde
Keyword(s):  
Excited States ◽  
Potential Energy Surfaces ◽  
Theoretical Study ◽  
Stable State ◽  
Structural Features ◽  
Stable Isomer ◽  
Spin Multiplicity ◽  
Linear Isomer ◽  
Energy Surfaces ◽  
Stable Linear

G2 methodology has been used to characterize minima on both doublet and quartet potential energy surfaces of the PSi2 radical system. We found that for states with doublet spin multiplicity the most stable isomer is the cyclic 2A1. Linear isomers lie more than 24 kcal/mol above in energy. For the quartets the most stable state isomer is the cyclic 4A2, and the most stable linear isomer, i.e., Si-Si-P(4∑−), lies 10.68 kcal/mol higher in energy. The structural features of the various isomers characterized have been rationalized in terms of the bonding features of the molecular orbitals involved. Key words: ab initio, excited states, radical.

Excited State Tracking During the Relaxation of Coordination Compounds

2018 ◽  
Author(s):  
Juan Sanz García ◽  
Martial Boggio-Pasqua ◽  
Ilaria Ciofini ◽  
Marco Campetella
Keyword(s):  
Excited State ◽  
Excited States ◽  
Potential Energy Surfaces ◽  
Photochemical Reactions ◽  
Complex Nature ◽  
Electronic Excited States ◽  
Ruthenium Nitrosyl ◽  
State Tracking ◽  
Energy Surfaces ◽  
Electronic Wavefunction

<div>The ability to locate minima on electronic excited states (ESs) potential energy surfaces (PESs) both in the case of bright and dark states is crucial for a full understanding of photochemical reactions. This task has become a standard practice for small- to medium-sized organic chromophores thanks to the constant developments in the field of computational photochemistry. However, this remains a very challenging effort when it comes to the optimization of ESs of transition metal complexes (TMCs), not only due to the presence of several electronic excited states close in energy, but also due to the complex nature of the excited states involved. In this article, we present a simple yet powerful method to follow an excited state of interest during a structural optimization in the case of TMC, based on the use of a compact hole-particle representation of the electronic transition, namely the natural transition orbitals (NTOs). State tracking using NTOs is unambiguously accomplished by computing the mono-electronic wavefunction overlap between consecutive steps of the optimization. Here, we demonstrate that this simple but robust procedure works not only in the case of the cytosine but also in the case of the ES optimization of a ruthenium-nitrosyl complex which is very problematic with standard approaches.</div>

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