Center for Molecular Modeling - K. Boguslawski

Non-Variational Orbital Optimization Techniques for the AP1roG Wave Function

wim — Mon, 24 Nov 2014 09:53:36 +0000

K. Boguslawski, P. Tecmer, P.W. Ayers, P. Bultinck, S. De Baerdemacker, D. Van Neck

Journal of Chemical Theory and Computation (JCTC)

10 (11), 4873-4882

2014

Abstract

We introduce new nonvariational orbital optimization schemes for the antisymmetric product of one-reference orbital geminal (AP1roG) wave function (also known as pair-coupled cluster doubles) that are extensions to our recently proposed projected seniority-two (PS2-AP1roG) orbital optimization method [ J. Chem. Phys. 2014, 140, 214114)]. These approaches represent less stringent approximations to the PS2-AP1roG ansatz and prove to be more robust approximations to the variational orbital optimization scheme than PS2-AP1roG. The performance of the proposed orbital optimization techniques is illustrated for a number of well-known multireference problems: the insertion of Be into H2, the automerization process of cyclobutadiene, the stability of the monocyclic form of pyridyne, and the aromatic stability of benzene.

DOI

http://dx.doi.org/10.1021/ct500759q

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14_JCTC_10(11)4873_Boguslawski.pdf

Efficient description of strongly correlated electrons with mean-field cost

wim — Tue, 23 Sep 2014 13:56:48 +0000

K. Boguslawski, P. Tecmer, P.W. Ayers, P. Bultinck, S. De Baerdemacker, D. Van Neck

Physical Review B

89 (20), 201106

2014

Abstract

We present an efficient approach to the electron correlation problem that is well suited for strongly interacting many-body systems, but requires only mean-field-like computational cost. The performance of our approach is illustrated for one-dimensional Hubbard rings with different numbers of sites, and for the nonrelativistic quantum-chemical Hamiltonian exploring the symmetric dissociation of the H-50 hydrogen chain.

Open Access version available at UGent repository

DOI

http://dx.doi.org/10.1103/PhysRevB.89.201106

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14_phys_rev_B_89,201106_Boguslawski.pdf

Projected seniority-two orbital optimization of the antisymmetric product of one-reference orbital geminal

Bernadette — Tue, 29 Jul 2014 13:33:13 +0000

K. Boguslawski, P. Tecmer, P.A. Limacher, P.A. Johnson, P.W. Ayers, P. Bultinck, S. De Baerdemacker, D. Van Neck

Journal of Chemical Physics

140 (21), 214114

2014

Abstract

We present a new, non-variational orbital-optimization scheme for the antisymmetric product of one-reference orbital geminal wave function. Our approach is motivated by the observation that an orbital-optimized seniority-zero configuration interaction (CI) expansion yields similar results to an orbital-optimized seniority-zero-plus-two CI expansion [L. Bytautas, T. M. Henderson, C. A. Jimenez-Hoyos, J. K. Ellis, and G. E. Scuseria, J. Chem. Phys. 135, 044119 (2011)]. A numerical analysis is performed for the C-2 and LiF molecules, for the CH2 singlet diradical as well as for the symmetric stretching of hypothetical (linear) hydrogen chains. For these test cases, the proposed orbital-optimization protocol yields similar results to its variational orbital optimization counterpart, but prevents symmetry-breaking of molecular orbitals in most cases. (C) 2014 AIP Publishing LLC.

DOI

http://dx.doi.org/10.1063/1.4880820

Assessing The Accuracy Of New Geminal-Based Approaches

toon — Tue, 22 Apr 2014 08:47:18 +0000

P. Tecmer, K. Boguslawski, P.A. Johnson, P.A. Limacher, M. Chan, T. Verstraelen, P.W. Ayers

Journal of Physical Chemistry A

118 (39), 9058–9068

2014

Abstract

We present a systematic theoretical study on the dissociation of diatomic molecules and their spectroscopic constants using our recently presented geminal-based wave function ansätze. Specifically, the performance of the antisymmetric product of rank two geminals (APr2G), the antisymmetric product of 1-reference-orbital geminals (AP1roG) and its orbital-optimized variant (OO-AP1roG) are assessed against standard quantum chemistry methods. Our study indicates that these new geminal-based approaches provide a cheap, robust, and accurate alternative for the description of bond-breaking processes in closed-shell systems requiring only mean-field-like computational cost. In particular, the spectroscopic constants obtained from OO-AP1roG are in very good agreement with reference theoretical and experimental data.

DOI

http://dx.doi.org/10.1021/jp502127v

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14_JPhysChemA_xx(x)xxx_Tecmer.pdf

14_JPhysChemA_118(39)9058_Tecmer.pdf

When two is better than one: the seniority scheme as a new tool to build wave functions

wim — Wed, 03 Feb 2016 11:17:26 +0000

S. De Baerdemacker, P. Claeys, W. Poelmans, D. Van Neck, P. Bultinck, M. Van Raemdonck, P.W. Ayers, P.A. Limacher, P.A. Johnson, K. Boguslawski, P. Tecmer

ISBN/ISSN:

Talk

Conference / event / venue

QCB12

Leuven, Belgium

Tuesday, 16 February, 2016

Abstract (private)

qcb12.pdf

Conference reference

Twelfth Edition of the Conference Quantum Chemistry in Belgium (QCB12)