Multicomponent Orbital-Optimized Perturbation Theory Methods: Approaching Coupled Cluster Accuracy at Lower Cost

Pavošević, Fabijan; Rousseau, Benjamin J.G.; Hammes‐Schiffer, Sharon

doi:10.1021/acs.jpclett.0c00090

Cited by 45 publications

(63 citation statements)

References 36 publications

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“…5 The quantum information metrics introduced here will enable us to fully automate these active-space-based methods, following the strategy of the AutoCAS algorithm 61,92-94 for electronic-structure calculations. Our future work will also focus on designing the multi-reference extension of nuclear-electronic perturbative 95,96 and CC-based approaches, 97,98 based on their electronic-structure counterpart, [99][100][101][102][103][104][105] to include efficiently the dynamical correlation lacking in active-space approaches. In this way, we will push NEHF-DMRG for molecules with multiple, near-degenerate protons that may display strong correlation effects.…”

Section: Discussionmentioning

confidence: 99%

Quantum Proton Effects from Density Matrix Renormalization Group Calculations

Feldmann,

Muolo,

Baiardi

et al. 2021

Preprint

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We recently introduced [J. Chem. Phys. 152 2020, 204103] the nuclear-electronic all-particle density matrix renormalization group method (NEAP-DMRG) to solve the molecular Schrödinger equation, based on a stochastically optimized orbital basis, without invoking the Born-Oppenheimer approximation. In this work, we combine the DMRG with nuclear-electronic Hartree-Fock (NEHF-DMRG), treating nuclei and electrons on the same footing. Inter-and intra-species correlations are described within the DMRG without truncating the excitation degree of the full configuration interaction wave function. We extend the concept of orbital entanglement and mutual information to nuclear-electronic wave functions and demonstrate that they are reliable metrics to detect strong correlation effects. We apply NEHF-DMRG to the HeHHe + molecular ion, to obtain accurate proton densities, ground-state total energies, and vibrational transition frequencies by comparison with state-of-the-art data obtained with grid-based approaches and modern configuration interaction methods. For HCN,

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Section: Discussionmentioning

confidence: 99%

Quantum Proton Effects from Density Matrix Renormalization Group Calculations

Feldmann,

Muolo,

Baiardi

et al. 2021

Preprint

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“…where d o refers to the occupied block of d in (26) and d v refers tothe virtual block in (27). C n is the nth Catalan number.…”

Section: Block Diagonal Structure Of D and γmentioning

confidence: 99%

“…The development of new DCT parameterizations is chiefly motivated [14][15][16][17] by the success of the orbital-optimized ODC-12 method. 18,19 The ODC-12 parameters consist of orbital rotation amplitudes [19][20][21][22][23][24][25][26][27][28][29] and rank two excitation-type amplitudes, analogous to those of orbital-optimized coupled cluster doubles. 22 The resulting ODC-12 method boasts superior accuracy to CCSD for the same computational scaling, 19,30,31 more tolerance of strong correlation than CCSD, 15 a straightforward analytic gradient theory, 19 and a response theory that is both efficient and hermitian.…”

Section: Introductionmentioning

confidence: 99%

Cumulants as the Variables of Density Cumulant Theory: A Path to Hermitian Triples

Misiewicz,

Turney,

Schaefer

2021

Preprint

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We study the combination of orbital-optimized density cumulant theory and a new parameterization of the reduced density matrices in which the variables are the particlehole cumulant elements. We call this combination OλDCT. We find that this new ansatz solves problems identified in the previous unitary coupled cluster ansatz for density cumulant theory: the theory is now free of near-zero denominators between occupied and virtual blocks, can correctly describe the dissociation of H 2 , and is rigorously size-extensive. In addition, the new ansatz has fewer terms than the previous unitary ansatz, and the optimal orbitals delivered by the exact theory are the natural orbitals. Numerical studies on systems amenable to full configuration interaction show that the amplitudes from the previous ODC-12 method approximate the exact amplitudes predicted by this ansatz. Studies on equilibrium properties of diatomic molecules show that even with the new ansatz, it is necessary to include triples to improve the accuracy of the method compared to orbital optimized linearized coupled cluster doubles. With a simple iterative triples correction, OλDCT outperforms other orbital-optimized methods truncated at comparable levels in the amplitudes, as well as CCSD(T). By adding four more terms to the cumulant parameterization, OλDCT outperforms CCSDT while having the same O(V 5 O 3 ) scaling.

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“…While automatic differentiation is becoming a standard technique in quantum computing or classical machine learning algorithms, it started to gain attention in classical quantum chemistry as well. Examples are within the optimization of basis set parameters, 26 classical coupled-cluster amplitudes, 27 response properties, 28 nuclear derivatives 29–31 or new frontiers in excited state methods. 32 In this work, we extend the framework of automatically differentiable quantum algorithms to unitary coupled-cluster in its separated framework.…”

Section: Introductionmentioning

confidence: 99%