Synergy between pair coupled cluster doubles and pair density functional theory

Garza, Alejandro J.; Bulik, Ireneusz W.; Henderson, Thomas M.; Scuseria, Gustavo E.

doi:10.1063/1.4906607

Cited by 38 publications

(66 citation statements)

References 55 publications

(65 reference statements)

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“…This can be achieved a posteriori using PT approaches, [46,47] coupled cluster corrections, [50,51] or DFT-type methods. [54,55] In this work, we have extended the previously presented PT models with an AP1roG reference function and benchmarked those models against spectroscopic constants for multiply bonded diatomics and thermochemical data extrapolated to the basis set limit. Most importantly, combining AP1roG with the investigated corrections allows us to reliably model molecular systems dominated by both static/nondynamic and dynamic electron correlation.…”

Section: Discussionmentioning

confidence: 99%

“…A different, computationally feasible approach suitable for strongly-correlated systems uses seniority-zero wavefunctions to describe the static/nondynamic part of the electron correlation en-ergy. [31][32][33][34][35][36][37][38][39][40][41][42][43][44] The missing dynamic electron correlation effects are included a posteriori in these ansätze using, for instance, many-body perturbation theory [45][46][47], coupled-cluster theory [48][49][50][51][52], extended random phase approximation [53], and density functional theory (DFT) corrections [54,55].…”

Section: Introductionmentioning

confidence: 99%

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Benchmark of Dynamic Electron Correlation Models for Seniority-Zero Wave Functions and Their Application to Thermochemistry

Boguslawski

Tecmer

2017

J. Chem. Theory Comput.

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Wavefunctions restricted to electron-pair states are promising models to describe static/nondynamic electron correlation effects encountered, for instance, in bond-dissociation processes and transition-metal and actinide chemistry. To reach spectroscopic accuracy, however, the missing dynamic electron correlation effects that cannot be described by electron-pair states need to be included a posteriori. In this article, we extend the previously presented perturbation theory models with an Antisymmetric Product of 1-reference orbital Geminal (AP1roG) reference function that allow us to describe both static/nondynamic and dynamic electron correlation effects. Specifically, our perturbation theory models combine a diagonal and off-diagonal zero-order Hamiltonian, a single-reference and multi-reference dual state, and different excitation operators used to construct the projection manifold. We benchmark all proposed models as well as an a posteriori linearized coupled cluster correction on top of AP1roG against CR-CCSD(T) reference data for reaction energies of several closed-shell molecules that are extrapolated to the basis set limit. Moreover, we test the performance of our new methods for multiple bond breaking processes in the N2, C2, and BN dimers against MRCI-SD and MRCI-SD+Q reference data. Our numerical results indicate that the best performance is obtained from a linearized coupled cluster correction as well as second-order perturbation theory corrections employing a diagonal and off-diagonal zero-order Hamiltonian and a single-determinant dual state. These dynamic corrections on top of AP1roG allow us to reliably model molecular systems dominated by static/nondynamic as well as dynamic electron correlation.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Benchmark of Dynamic Electron Correlation Models for Seniority-Zero Wave Functions and Their Application to Thermochemistry

Boguslawski

Tecmer

2017

J. Chem. Theory Comput.

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“…The most significant is that pECCD does not include dynamic correlation. One can attempt to fix this with the addition of a simple density functional correlation energy, 25 or by relaxing the restriction to seniority zero, whether by freezing amplitudes 8,9 or, potentially, by including a perturbative account for higher seniority sectors. Moreover, the restriction to seniority zero is sometimes too severe; some systems simply require higher seniority sectors for the description of strong correlation effects, as is seen, for example, in the dissociation of N 2 .…”

Section: Discussionmentioning

confidence: 99%

Pair extended coupled cluster doubles

Henderson

Bulik

Scuseria

2015

The Journal of Chemical Physics

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The accurate and efficient description of strongly correlated systems remains an important challenge for computational methods. Doubly occupied configuration interaction (DOCI), in which all electrons are paired and no correlations which break these pairs are permitted, can in many cases provide an accurate account of strong correlations, albeit at combinatorial computational cost. Recently, there has been significant interest in a method we refer to as pair coupled cluster doubles (pCCD), a variant of coupled cluster doubles in which the electrons are paired. This is simply because pCCD provides energies nearly identical to those of DOCI, but at mean-field computational cost (disregarding the cost of the two-electron integral transformation). Here, we introduce the more complete pair extended coupled cluster doubles (pECCD) approach which, like pCCD, has mean-field cost and reproduces DOCI energetically. We show that unlike pCCD, pECCD also reproduces the DOCI wave function with high accuracy. Moreoever, pECCD yields sensible albeit inexact results even for attractive interactions where pCCD breaks down.

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“…33,41,57,62), we use the P 2 (r) formulation (eqn (2)) of KS-DFT 63 to circumvent the symmetry dilemma. The alternative spin density is defined as…”

Section: Alternative Densitiesmentioning

confidence: 99%

“…33,41,57,62 There are, however, a few drawbacks in this approach. When using MR densities, m(r) in eqn (2) can become complex in certain strongly correlated systems.…”

Section: Introductionmentioning

confidence: 96%

Range separated hybrids of pair coupled cluster doubles and density functionals

Garza

Bulik

Henderson

et al. 2015

Phys. Chem. Chem. Phys.

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Pair coupled cluster doubles (pCCD) is a size-consistent, size-extensive, low-cost simplification of CCD that has been shown to be able to describe static correlation without breaking symmetry. We combine pCCD with Kohn-Sham functionals of the density and the local pair density in order to incorporate dynamic correlation in pCCD while maintaining its low cost. Double counting is eliminated by splitting the (interelectron) Coulomb operator into complementary short- and long-range parts, and evaluating the two-body energy with pCCD in the long-range and with density functionals in the short-range. This simultaneously suppresses self-interaction in the Hartree-exchange term of the functionals. Generalizations including a fraction of wavefunction two-body energy in the short-range are also derived and studied. The improvement of our pCCD+DFT hybrids over pCCD is demonstrated in calculations on benchmarks where both types of correlation are important.

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Synergy between pair coupled cluster doubles and pair density functional theory

Cited by 38 publications

References 55 publications

Benchmark of Dynamic Electron Correlation Models for Seniority-Zero Wave Functions and Their Application to Thermochemistry

Benchmark of Dynamic Electron Correlation Models for Seniority-Zero Wave Functions and Their Application to Thermochemistry

Pair extended coupled cluster doubles

Range separated hybrids of pair coupled cluster doubles and density functionals

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