A pair natural orbital implementation of the coupled cluster model CC2 for excitation energies

2013 ◽  
Vol 139 (8) ◽  
pp. 084114 ◽  
Author(s):  
Benjamin Helmich ◽  
Christof Hättig
Keyword(s):  
Cluster Model ◽  
Coupled Cluster ◽  
Natural Orbital ◽  
Excitation Energies

Inclusion of the (T) triples correction into the linear-r12 corrected coupled-cluster model CCSD(R12)

2006 ◽  
Vol 106 (11) ◽  
pp. 2306-2317 ◽  
Author(s):  
Heike Fliegl ◽  
Christof Hättig ◽  
Wim Klopper
Keyword(s):  
Cluster Model ◽  
Coupled Cluster

Tensor Hypercontraction Equation-of-Motion Second-Order Approximate Coupled Cluster: Electronic Excitation Energies in O(N4) Time

2013 ◽  
Vol 117 (42) ◽  
pp. 12972-12978 ◽  
Author(s):  
Edward G. Hohenstein ◽  
Sara I. L. Kokkila ◽  
Robert M. Parrish ◽  
Todd J. Martínez
Keyword(s):  
Electronic Excitation ◽  
Equation Of Motion ◽  
Second Order ◽  
Coupled Cluster ◽  
Excitation Energies

scholarly journals A New Benchmark Set for Excitation Energy of Charge Transfer States: Systematic Investigation of Coupled-Cluster Type Methods

2020 ◽  
Author(s):  
Balázs Kozma ◽  
Attila Tajti ◽  
Baptiste Demoulin ◽  
Róbert Izsák ◽  
Marcel Nooijen ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Excitation Energy ◽  
Systematic Investigation ◽  
Coupled Cluster ◽  
Excitation Energies ◽  
Chemical Methods ◽  
Valence States ◽  
Quantum Chemical Methods ◽  
Material Physics ◽  
Cluster Methods

There are numerous publications on benchmarking quantum chemistry methods for excited states. These studies rarely include Charge Transfer (CT) states although many interesting phenomena in e.g. biochemistry and material physics involve transfer of electron between fragments of the system. Therefore, it is timely to test the accuracy of quantum chemical methods for CT states, as well. In this study we first suggest a set benchmark systems consisting of dimers having low-energy CT states. On this set, the excitation energy has been calculated with coupled cluster methods including triple excitations (CC3, CCSDT-3, CCSD(T)(a)* ), as well as with methods including full or approximate doubles (CCSD, STEOM-CCSD, CC2, ADC(2), EOM-CCSD(2)). The results show that the popular CC2 and ADC(2) methods are much more inaccurate for CT states than for valence states. On the other hand, CCSD seems to have similar systematic overestimation of the excitation energies for both valence and CT states. Concerning triples methods, the new CCSD(T)(a)* method including non-iterative triple excitations preforms very well for all type of states, delivering essentially CCSDT quality results.<br>

scholarly journals Complex ground-state and excitation energies in coupled-cluster theory

2021 ◽  
pp. e1968056
Author(s):  
Simon Thomas ◽  
Florian Hampe ◽  
Stella Stopkowicz ◽  
Jürgen Gauss
Keyword(s):  
Ground State ◽  
Coupled Cluster ◽  
Excitation Energies ◽  
Coupled Cluster Theory ◽  
Cluster Theory

The Fock-Space Coupled-Cluster Method in the Calculation of Excited State Properties

2005 ◽  
Vol 70 (6) ◽  
pp. 811-825 ◽  
Author(s):  
Monika Musiał ◽  
Leszek Meissner
Keyword(s):  
Experimental Data ◽  
Excited States ◽  
Fock Space ◽  
Hamiltonian Formulation ◽  
Basis Sets ◽  
Cluster Method ◽  
Coupled Cluster ◽  
Coupled Cluster Method ◽  
Excitation Energies ◽  
Equilibrium Geometries

Our recently developed intermediate Hamiltonian Fock-space coupled-cluster (FS-CC) method with singles and doubles is applied to calculation of equilibrium geometries, harmonic frequencies and adiabatic excitation energies for some excited states of N2 and CO. Due to the intermediate Hamiltonian formulation, which provides a robust computational scheme for solving the FS-CC equations, and the efficient factorization strategy, relatively large basis sets and reference spaces are employed permitting a comparison of calculated properties with experimental data.

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