Towards a spin-adapted coupled-cluster theory for high-spin open-shell states

Heckert, Miriam; Heun, Oliver; Gauß, Jürgen; Szalay, Péter G.

doi:10.1063/1.2179070

Cited by 55 publications

(44 citation statements)

References 47 publications

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“…In calculations of the doublet state of the uracil anion we used an approximate spin adaptation of the double excitation amplitudes in CCSD, which are then used for the perturbative treatment of triples [24,33]. This method leads to energies which are very close to the energies obtained by the rigorous, but slightly more demanding method [34] for the spin adaptation. Denominators in perturbatively calculated triples are the diagonal Fock matrix elements [24].…”

Section: Methodsmentioning

confidence: 92%

CCSD(T) calculations of the electron affinity of the uracil molecule

Dedíková

Demovič

Pitoňák

et al. 2009

Chemical Physics Letters

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Section: Methodsmentioning

confidence: 92%

CCSD(T) calculations of the electron affinity of the uracil molecule

Dedíková

Demovič

Pitoňák

et al. 2009

Chemical Physics Letters

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“…22−24,30 Because of the high computational demands of CCSD(T), the MP2 method(25) was also used. The ( n – 1)p 6 ( n – 1)d 10 shells of palladium and ( n – 1)p 6 ( n – 1)d 10 n s 1 shells of silver and gold were correlated.…”

Section: Calculationsmentioning

confidence: 99%

The Nature of the Binding of Au, Ag, and Pd to Benzene, Coronene, and Graphene: From Benchmark CCSD(T) Calculations to Plane-Wave DFT Calculations

Granatier

Lazar

Otyepka

et al. 2011

J. Chem. Theory Comput.

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The adsorption of Ag, Au, and Pd atoms on benzene, coronene, and graphene has been studied using post Hartree–Fock wave function theory (CCSD(T), MP2) and density functional theory (M06-2X, DFT-D3, PBE, vdW-DF) methods. The CCSD(T) benchmark binding energies for benzene–M (M = Pd, Au, Ag) complexes are 19.7, 4.2, and 2.3 kcal/mol, respectively. We found that the nature of binding of the three metals is different: While silver binds predominantly through dispersion interactions, the binding of palladium has a covalent character, and the binding of gold involves a subtle combination of charge transfer and dispersion interactions as well as relativistic effects. We demonstrate that the CCSD(T) benchmark binding energies for benzene–M complexes can be reproduced in plane-wave density functional theory calculations by including a fraction of the exact exchange and a nonempirical van der Waals correction (EE+vdW). Applying the EE+vdW method, we obtained binding energies for the graphene–M (M = Pd, Au, Ag) complexes of 17.4, 5.6, and 4.3 kcal/mol, respectively. The trends in binding energies found for the benzene–M complexes correspond to those in coronene and graphene complexes. DFT methods that use empirical corrections to account for the effects of vdW interactions significantly overestimate binding energies in some of the studied systems.

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“…Another important development is the spin-restricted CC theory of Szalay and Gauss 63 and its extension to a spinadapted CC approach proposed very recently. 64 While it seems that the unitary group parametrization of cluster operators is mandatory for formulating a rigorously spin-adapted CC theory, a pure exponential structure of the wave operator seems to be a subject of further thorough investigation. The pure exponential form of the wave operator with commuting cluster operators in the closed-shell CC theory or in the spin-orbital based open-shell CC theory provides a physically correct description of the various powers of cluster operators in the wave-operator expansion.…”

Section: Introductionmentioning

confidence: 99%

An explicitly spin-free compact open-shell coupled cluster theory using a multireference combinatoric exponential ansatz: Formal development and pilot applications

Datta

Mukherjee

2009

The Journal of Chemical Physics

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In this paper, we present a comprehensive account of an explicitly spin-free compact state-universal multireference coupled cluster (CC) formalism for computing the state energies of simple open-shell systems, e.g., doublets and biradicals, where the target open-shell states can be described by a few configuration state functions spanning a model space. The cluster operators in this formalism are defined in terms of the spin-free unitary generators with respect to the common closed-shell component of all model functions (core) as vacuum. The spin-free cluster operators are either closed-shell-like n hole-n particle excitations (denoted by T(mu)) or involve excitations from the doubly occupied (nonvalence) orbitals to the singly occupied (valence) orbitals (denoted by S(e)(mu)). In addition, there are cluster operators with exchange spectator scatterings involving the valence orbitals (denoted by S(re)(mu)). We propose a new multireference cluster expansion ansatz for the wave operator with the above generally noncommuting cluster operators which essentially has the same physical content as the Jeziorski-Monkhorst ansatz with the commuting cluster operators defined in the spin-orbital basis. The T(mu) operators in our ansatz are taken to commute with all other operators, while the S(e)(mu) and S(re)(mu) operators are allowed to contract among themselves through the spectator valence orbitals. An important innovation of this ansatz is the choice of an appropriate automorphic factor accompanying each contracted composite of cluster operators in order to ensure that each distinct excitation generated by this composite appears only once in the wave operator. The resulting CC equations consist of two types of terms: a "direct" term and a "normalization" term containing the effective Hamiltonian operator. It is emphasized that the direct term is almost quartic in the cluster amplitudes, barring only a handful of terms and termination of the normalization term depends on the valence rank of the effective Hamiltonian operator and the excitation rank of the cluster operators at which the theory is truncated. Illustrative applications are presented by computing the state energies of neutral doublet radicals and doublet molecular cations and ionization energies of neutral molecules and comparing our results with the other open-shell CC theories, benchmark full CI results (when available) in the same basis, and the experimental results. Highly encouraging results show the efficacy of the method.

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Towards a spin-adapted coupled-cluster theory for high-spin open-shell states

Cited by 55 publications

References 47 publications

CCSD(T) calculations of the electron affinity of the uracil molecule

CCSD(T) calculations of the electron affinity of the uracil molecule

The Nature of the Binding of Au, Ag, and Pd to Benzene, Coronene, and Graphene: From Benchmark CCSD(T) Calculations to Plane-Wave DFT Calculations

An explicitly spin-free compact open-shell coupled cluster theory using a multireference combinatoric exponential ansatz: Formal development and pilot applications

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