1
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Zhao Z, Filip MA, Thom AJW. Rapidly convergent quantum Monte Carlo using a Chebyshev projector. Faraday Discuss 2024. [PMID: 39083360 DOI: 10.1039/d4fd00035h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/02/2024]
Abstract
The multireference coupled-cluster Monte Carlo (MR-CCMC) algorithm is a determinant-based quantum Monte Carlo (QMC) algorithm that is conceptually similar to Full Configuration Interaction QMC (FCIQMC). It has been shown to offer a balanced treatment of both static and dynamic correlation while retaining polynomial scaling, although application to large systems with significant strong correlation remained impractical. In this paper, we document recent algorithmic advances that enable rapid convergence and a more black-box approach to the multireference problem. These include a logarithmically scaling metric-tree-based excitation acceptance algorithm to search for determinants connected to the reference space at the desired excitation level and a symmetry-screening procedure for the reference space. We show that, for moderately sized reference spaces, the new search algorithm brings about an approximately 8-fold acceleration of one MR-CCMC iteration, while the symmetry screening procedure reduces the number of active reference space determinants with essentially no loss of accuracy. We also introduce a stochastic implementation of an approximate wall projector, which is the infinite imaginary time limit of the exponential projector, using a truncated expansion of the wall function in Chebyshev polynomials. Notably, this wall-Chebyshev projector can be used to accelerate any projector-based QMC algorithm. We show that it requires significantly fewer applications of the Hamiltonian to achieve the same statistical convergence. We benchmark these acceleration methods on the beryllium and carbon dimers, using initiator FCIQMC and MR-CCMC with basis sets up to cc-pVQZ quality.
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Affiliation(s)
- Zijun Zhao
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK.
| | - Maria-Andreea Filip
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK.
| | - Alex J W Thom
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK.
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2
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Kats D, Christlmaier EMC, Schraivogel T, Alavi A. Orbital optimisation in xTC transcorrelated methods. Faraday Discuss 2024. [PMID: 39072553 DOI: 10.1039/d4fd00036f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/30/2024]
Abstract
We present a combination of the bi-orthogonal orbital optimisation framework with the recently introduced xTC version of transcorrelation. This allows us to implement non-iterative perturbation based methods on top of the transcorrelated Hamiltonian. Additionally, the orbital optimisation influences results of other truncated methods, such as the distinguishable cluster with singles and doubles. The accuracy of these methods in comparison to standard xTC methods is demonstrated, and the advantages and disadvantages of the orbital optimisation are discussed.
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Affiliation(s)
- Daniel Kats
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany.
| | | | - Thomas Schraivogel
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany.
| | - Ali Alavi
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany.
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3
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Dobrautz W, Sokolov IO, Liao K, Ríos PL, Rahm M, Alavi A, Tavernelli I. Toward Real Chemical Accuracy on Current Quantum Hardware Through the Transcorrelated Method. J Chem Theory Comput 2024; 20:4146-4160. [PMID: 38723159 PMCID: PMC11137825 DOI: 10.1021/acs.jctc.4c00070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Revised: 04/15/2024] [Accepted: 04/16/2024] [Indexed: 05/29/2024]
Abstract
Quantum computing is emerging as a new computational paradigm with the potential to transform several research fields including quantum chemistry. However, current hardware limitations (including limited coherence times, gate infidelities, and connectivity) hamper the implementation of most quantum algorithms and call for more noise-resilient solutions. We propose an explicitly correlated Ansatz based on the transcorrelated (TC) approach to target these major roadblocks directly. This method transfers, without any approximation, correlations from the wave function directly into the Hamiltonian, thus reducing the resources needed to achieve accurate results with noisy quantum devices. We show that the TC approach allows for shallower circuits and improves the convergence toward the complete basis set limit, providing energies within chemical accuracy to experiment with smaller basis sets and, thus, fewer qubits. We demonstrate our method by computing bond lengths, dissociation energies, and vibrational frequencies close to experimental results for the hydrogen dimer and lithium hydride using two and four qubits, respectively. To demonstrate our approach's current and near-term potential, we perform hardware experiments, where our results confirm that the TC method paves the way toward accurate quantum chemistry calculations already on today's quantum hardware.
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Affiliation(s)
- Werner Dobrautz
- Department
of Chemistry and Chemical Engineering, Chalmers
University of Technology, 41296 Gothenburg, Sweden
| | - Igor O. Sokolov
- IBM
Quantum, IBM Research Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - Ke Liao
- Max
Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
| | - Pablo López Ríos
- Max
Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
| | - Martin Rahm
- Department
of Chemistry and Chemical Engineering, Chalmers
University of Technology, 41296 Gothenburg, Sweden
| | - Ali Alavi
- Max
Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Lensfield
Road, Cambridge CB2 1EW, U.K.
| | - Ivano Tavernelli
- IBM
Quantum, IBM Research Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
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4
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Safari AA, Anderson RJ, Manni GL. Toward a Stochastic Complete Active Space Second-Order Perturbation Theory. J Phys Chem A 2024; 128:281-291. [PMID: 38154124 PMCID: PMC10788896 DOI: 10.1021/acs.jpca.3c05109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 11/14/2023] [Accepted: 11/14/2023] [Indexed: 12/30/2023]
Abstract
In this work, an internally contracted stochastic complete active space second-order perturbation theory, stochastic-CASPT2, is reported. The method relies on stochastically sampled reduced density matrices (RDMs) up to rank four and contractions thereof with the generalized Fock matrix. A new protocol for calculating higher-order RDMs in full configuration interaction quantum Monte Carlo (FCIQMC) has been designed based on (1) restricting sampling of the corresponding excitations to a deterministic subspace, (2) averaging the RDMs from independent dynamics and (3) projecting them onto the closest positive semi-definite matrix. Our protocol avoids previously encountered numerical conditioning problems in the orthogonalization of the perturber overlap matrix stemming from numerical noise. The chromium dimer CASSCF(12,12)/CASPT2 binding curve is computed as a proof of concept.
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Affiliation(s)
- Arta A. Safari
- Max-Planck-Institute for Solid State
Research, 70569 Stuttgart, Germany
| | | | - Giovanni Li Manni
- Max-Planck-Institute for Solid State
Research, 70569 Stuttgart, Germany
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5
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Ammar A, Scemama A, Giner E. Transcorrelated selected configuration interaction in a bi-orthonormal basis and with a cheap three-body correlation factor. J Chem Phys 2023; 159:114121. [PMID: 37732558 DOI: 10.1063/5.0163831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 08/21/2023] [Indexed: 09/22/2023] Open
Abstract
In this work, we develop a mathematical framework for a selected configuration interaction (SCI) algorithm within a bi-orthogonal basis for transcorrelated (TC) calculations. The bi-orthogonal basis used here serves as the equivalent of the standard Hartree-Fock (HF) orbitals. However, within the context of TC, it leads to distinct orbitals for the left and right vectors. Our findings indicate that the use of such a bi-orthogonal basis allows for a proper definition of the frozen core approximation. In contrast, the use of HF orbitals results in bad error cancellations for ionization potentials and atomization energies (AE). Compared to HF orbitals, the optimized bi-orthogonal basis significantly reduces the positive part of the second-order energy (PT2), thereby facilitating the use of standard extrapolation techniques of hermitian SCI. While we did not observe a significant improvement in the convergence of the SCI algorithm, this is largely due to the use in this work of a simple three-body correlation factor introduced in a recent study. This correlation factor, which depends only on atomic parameters, eliminates the need for re-optimization of the correlation factor for molecular systems, making its use straightforward and user-friendly. Despite the simplicity of this correlation factor, we were able to achieve accurate results on the AE of a series of 14 molecules on a triple-zeta basis. We also successfully broke a double bond until the full dissociation limit while maintaining the size consistency property. This work thus demonstrates the potential of the BiO-TC-SCI approach in handling complex molecular systems.
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Affiliation(s)
- Abdallah Ammar
- Laboratoire de Chimie et Physique Quantiques (UMR 5626), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Anthony Scemama
- Laboratoire de Chimie et Physique Quantiques (UMR 5626), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Emmanuel Giner
- Laboratoire de Chimie Théorique, Sorbonne Université and CNRS, F-75005 Paris, France
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6
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Lee N, Thom AJW. Studies on the Transcorrelated Method. J Chem Theory Comput 2023; 19:5743-5759. [PMID: 37640393 PMCID: PMC10500994 DOI: 10.1021/acs.jctc.3c00046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Indexed: 08/31/2023]
Abstract
We investigate the possibility of using a transcorrelated (TC) Hamiltonian to describe electron correlation. A method to obtain TC wavefunctions was developed based on the mathematical framework of the bi-variational principle. This involves the construction of an effective TC Hamiltonian matrix, which can be solved in a self-consistent manner. This was optimized using a method we call second-order-moment minimization and demonstrate that it is possible to obtain highly accurate energies for some closed-shell atoms and helium-like ions. The effects of certain correlator terms on the description of electron-electron and electron-nuclear cusps were also examined graphically, and some TC wavefunctions were compared against near-exact Hylleraas wavefunctions.
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Affiliation(s)
- Nicholas Lee
- Department
of Chemistry, Physical and Theoretical Chemistry
Laboratory, South Parks
Road, Oxford OX1 3QZ, U.K.
| | - Alex J. W. Thom
- Yusuf
Hamied Department of Chemistry, Lensfield Road, Cambridge CB2 1EW, U.K.
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7
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Ammar A, Scemama A, Giner E. Biorthonormal Orbital Optimization with a Cheap Core-Electron-Free Three-Body Correlation Factor for Quantum Monte Carlo and Transcorrelation. J Chem Theory Comput 2023. [PMID: 37390472 DOI: 10.1021/acs.jctc.3c00257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/02/2023]
Abstract
We introduce a novel three-body correlation factor that is designed to vanish in the core region around each nucleus and approach a universal two-body correlation factor for valence electrons. The transcorrelated Hamiltonian is used to optimize the orbitals of a single Slater determinant within a biorthonormal framework. The Slater-Jastrow wave function is optimized on a set of atomic and molecular systems containing both second-row elements and 3d transition metal elements. The optimization of the correlation factor and the orbitals, along with an increase in the basis set, results in a systematic lowering of the variational Monte Carlo energy for all systems tested. Importantly, the optimal parameters of the correlation factor obtained for atomic systems can be transferred to molecules. Additionally, the present correlation factor is computationally efficient and uses a mixed analytical-numerical integration scheme that reduces the costly numerical integration from R6 to R3.
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Affiliation(s)
- Abdallah Ammar
- Laboratoire de Chimie et Physique Quantiques (UMR 5626), Université de Toulouse, CNRS, UPS, 31062 Toulouse, France
| | - Anthony Scemama
- Laboratoire de Chimie et Physique Quantiques (UMR 5626), Université de Toulouse, CNRS, UPS, 31062 Toulouse, France
| | - Emmanuel Giner
- Laboratoire de Chimie Théorique, Sorbonne Université and CNRS, F-75005 Paris, France
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8
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Haupt JP, Hosseini SM, López Ríos P, Dobrautz W, Cohen A, Alavi A. Optimizing Jastrow factors for the transcorrelated method. J Chem Phys 2023; 158:2895246. [PMID: 37290083 DOI: 10.1063/5.0147877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 05/25/2023] [Indexed: 06/10/2023] Open
Abstract
We investigate the optimization of flexible tailored real-space Jastrow factors for use in the transcorrelated (TC) method in combination with highly accurate quantum chemistry methods, such as initiator full configuration interaction quantum Monte Carlo (FCIQMC). Jastrow factors obtained by minimizing the variance of the TC reference energy are found to yield better, more consistent results than those obtained by minimizing the variational energy. We compute all-electron atomization energies for the challenging first-row molecules C2, CN, N2, and O2 and find that the TC method yields chemically accurate results using only the cc-pVTZ basis set, roughly matching the accuracy of non-TC calculations with the much larger cc-pV5Z basis set. We also investigate an approximation in which pure three-body excitations are neglected from the TC-FCIQMC dynamics, saving storage and computational costs, and show that it affects relative energies negligibly. Our results demonstrate that the combination of tailored real-space Jastrow factors with the multi-configurational TC-FCIQMC method provides a route to obtaining chemical accuracy using modest basis sets, obviating the need for basis-set extrapolation and composite techniques.
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Affiliation(s)
- J Philip Haupt
- Max-Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
| | | | - Pablo López Ríos
- Max-Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
| | - Werner Dobrautz
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Gothenburg, Sweden
| | - Aron Cohen
- DeepMind, 6 Pancras Square, London N1C 4AG, United Kingdom
| | - Ali Alavi
- Max-Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
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9
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Liao K, Zhai H, Christlmaier EM, Schraivogel T, Ríos PL, Kats D, Alavi A. Density Matrix Renormalization Group for Transcorrelated Hamiltonians: Ground and Excited States in Molecules. J Chem Theory Comput 2023; 19:1734-1743. [PMID: 36912635 DOI: 10.1021/acs.jctc.2c01207] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/14/2023]
Abstract
We present the theory of a density matrix renormalization group (DMRG) algorithm which can solve for both the ground and excited states of non-Hermitian transcorrelated Hamiltonians and show applications in molecular systems. Transcorrelation (TC) accelerates the basis set convergence rate by including known physics (such as, but not limited to, the electron-electron cusp) in the Jastrow factor used for the similarity transformation. It also improves the accuracy of approximate methods such as coupled cluster singles and doubles (CCSD) as shown by recent studies. However, the non-Hermiticity of the TC Hamiltonians poses challenges for variational methods like DMRG. Imaginary-time evolution on the matrix product state (MPS) in the DMRG framework has been proposed to circumvent this problem, but this is currently limited to treating the ground state and has lower efficiency than the time-independent DMRG (TI-DMRG) due to the need to eliminate Trotter errors. In this work, we show that with minimal changes to the existing TI-DMRG algorithm, namely, replacing the original Davidson solver with the general Davidson solver to solve the non-Hermitian effective Hamiltonians at each site for a few low-lying right eigenstates, and following the rest of the original DMRG recipe, one can find the ground and excited states with improved efficiency compared to the original DMRG when extrapolating to the infinite bond dimension limit in the same basis set. An accelerated basis set convergence rate is also observed, as expected, within the TC framework.
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Affiliation(s)
- Ke Liao
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Huanchen Zhai
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | | | - Thomas Schraivogel
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
| | - Pablo López Ríos
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
| | - Daniel Kats
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
| | - Ali Alavi
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany.,Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
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10
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Luo H, Alavi A. Perturbation Calculation of the Uniform Electron Gas with a Transcorrelated Hamiltonian. J Chem Phys 2022; 157:074105. [DOI: 10.1063/5.0101776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
With a transcorrelated Hamiltonian, we perform a many body perturbation (MBPT) calculation on the uniform electron gas in the high density regime. By using a correlation factor optimised for a single determinant Jastrow ansatz, the second order correlation energy is calculated as $\frac{1-\ln2}{\pi^{2}}\ln(r_{s})-0.05075$. This already reproduces the exact logarithmic term of the random phase approximation (RPA) result, while the constant term is roughly $7\%$ larger than the RPA one. The close agreement with the RPA method demonstrates that the transcorrelated method offers a viable and potentially efficient method for treating metallic systems.
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Affiliation(s)
- Hongjun Luo
- Max-Planck-Institute for Solid State Research, Germany
| | - Ali Alavi
- Max-Planck-Institute for Solid State Research, Germany
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11
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Dobrautz W, Cohen AJ, Alavi A, Giner E. Performance of a one-parameter correlation factor for transcorrelation: Study on a series of second row atomic and molecular systems. J Chem Phys 2022; 156:234108. [PMID: 35732534 DOI: 10.1063/5.0088981] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this work, we investigate the performance of a recently proposed transcorrelated (TC) approach based on a single-parameter correlation factor [E. Giner, J. Chem. Phys. 154, 084119 (2021)] for systems involving more than two electrons. The benefit of such an approach relies on its simplicity as efficient numerical-analytical schemes can be set up to compute the two- and three-body integrals occurring in the effective TC Hamiltonian. To obtain accurate ground state energies within a given basis set, the present TC scheme is coupled to the recently proposed TC-full configuration interaction quantum Monte Carlo method [Cohen et al., J. Chem. Phys. 151, 061101 (2019)]. We report ground state total energies on the Li-Ne series, together with their first cations, computed with increasingly large basis sets and compare to more elaborate correlation factors involving electron-electron-nucleus coordinates. Numerical results on the Li-Ne ionization potentials show that the use of the single-parameter correlation factor brings on average only a slightly lower accuracy (1.2 mH) in a triple-zeta quality basis set with respect to a more sophisticated correlation factor. However, already using a quadruple-zeta quality basis set yields results within chemical accuracy to complete basis set limit results when using this novel single-parameter correlation factor. Calculations on the H2O, CH2, and FH molecules show that a similar precision can be obtained within a triple-zeta quality basis set for the atomization energies of molecular systems.
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Affiliation(s)
- Werner Dobrautz
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
| | - Aron J Cohen
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
| | - Ali Alavi
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
| | - Emmanuel Giner
- Laboratoire de Chimie Théorique, Sorbonne Université and CNRS, F-75005 Paris, France
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12
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Baiardi A, Lesiuk M, Reiher M. Explicitly Correlated Electronic Structure Calculations with Transcorrelated Matrix Product Operators. J Chem Theory Comput 2022; 18:4203-4217. [PMID: 35666238 DOI: 10.1021/acs.jctc.2c00167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this work, we present the first implementation of the transcorrelated electronic Hamiltonian in an optimization procedure for matrix product states by the density matrix renormalization group (DMRG) algorithm. In the transcorrelation ansatz, the electronic Hamiltonian is similarity-transformed with a Jastrow factor to describe the cusp in the wave function at electron-electron coalescence. As a result, the wave function is easier to approximate accurately with the conventional expansion in terms of one-particle basis functions and Slater determinants. The transcorrelated Hamiltonian in first quantization comprises up to three-body interactions, which we deal with in the standard way by applying robust density fitting to two- and three-body integrals entering the second-quantized representation of this Hamiltonian. The lack of hermiticity of the transcorrelated Hamiltonian is taken care of along the lines of the first work on transcorrelated DMRG [ J. Chem. Phys. 2020, 153, 164115] by encoding it as a matrix product operator and optimizing the corresponding ground state wave function with imaginary-time time-dependent DMRG. We demonstrate our quantum chemical transcorrelated DMRG approach at the example of several atoms and first-row diatomic molecules. We show that transcorrelation improves the convergence rate to the complete basis set limit in comparison to conventional DMRG. Moreover, we study extensions of our approach that aim at reducing the cost of handling the matrix product operator representation of the transcorrelated Hamiltonian.
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Affiliation(s)
- Alberto Baiardi
- Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Michał Lesiuk
- Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland.,Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland
| | - Markus Reiher
- Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
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13
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Weser O, Liebermann N, Kats D, Alavi A, Li Manni G. Spin Purification in Full-CI Quantum Monte Carlo via a First-Order Penalty Approach. J Phys Chem A 2022; 126:2050-2060. [PMID: 35298155 PMCID: PMC8978180 DOI: 10.1021/acs.jpca.2c01338] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
![]()
In this article,
we demonstrate that a first-order spin penalty
scheme can be efficiently applied to the Slater determinant based
Full-CI Quantum Monte Carlo (FCIQMC) algorithm, as a practical route
toward spin purification. Two crucial applications are presented to
demonstrate the validity and robustness of this scheme: the 1Δg ← 3Σg vertical excitation in O2 and
key spin gaps in a [Mn3(IV)O4] cluster.
In the absence of a robust spin adaptation/purification technique,
both applications would be unattainable by Slater determinant based
ground state methods, with any starting wave function collapsing into
the higher-spin ground state during the optimization. This strategy
can be coupled to other algorithms that use the Slater determinant
based FCIQMC algorithm as configuration interaction eigensolver, including
the Stochastic Generalized Active Space, the similarity-transformed
FCIQMC, the tailored-CC, and second-order perturbation theory approaches.
Moreover, in contrast to the GUGA-FCIQMC technique, this strategy
features both spin projection and total spin adaptation, making it
appealing when solving anisotropic Hamiltonians. It also provides
spin-resolved reduced density matrices, important for the investigation
of spin-dependent properties in polynuclear transition metal clusters,
such as the hyperfine-coupling constants.
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Affiliation(s)
- Oskar Weser
- Max-Planck-Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Niklas Liebermann
- Max-Planck-Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Daniel Kats
- Max-Planck-Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Ali Alavi
- Max-Planck-Institute for Solid State Research, 70569 Stuttgart, Germany.,Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K
| | - Giovanni Li Manni
- Max-Planck-Institute for Solid State Research, 70569 Stuttgart, Germany
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14
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Affiliation(s)
- Markus Reiher
- ETH Zürich, Laboratorium für Physikalische Chemie Vladimir-Prelog-Weg 2 8093 Zürich Switzerland
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15
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Schraivogel T, Cohen AJ, Alavi A, Kats D. Transcorrelated coupled cluster methods. J Chem Phys 2021; 155:191101. [PMID: 34800963 DOI: 10.1063/5.0072495] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Transcorrelated coupled cluster and distinguishable cluster methods are presented. The Hamiltonian is similarity transformed with a Jastrow factor in the first quantization, which results in up to three-body integrals. The coupled cluster with singles and doubles equations on this transformed Hamiltonian are formulated and implemented. It is demonstrated that the resulting methods have a superior basis set convergence and accuracy to the corresponding conventional and explicitly correlated methods. Additionally, approximations for three-body integrals are suggested and tested.
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Affiliation(s)
- Thomas Schraivogel
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Aron J Cohen
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Ali Alavi
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Daniel Kats
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
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