Systematic Expansion of Active Spaces beyond the CASSCF Limit: A GASSCF/SplitGAS Benchmark Study

Vogiatzis, Konstantinos D.; Manni, Giovanni Li; Stoneburner, Samuel J.; Ma, Dongxia; Gagliardi, Laura

doi:10.1021/acs.jctc.5b00191

Cited by 57 publications

(72 citation statements)

References 87 publications

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“…However, the number of CSFs increases factorially with the number of active orbitals, and the largest calculations so far included 22 electrons in 22 active orbitals. 73 One way of tackling the exploding number of configuration is to divide the active space into subsets and to add occupation restrictions to each subspace, as for example in the restricted active space (RAS) 9,74 or the generalized active space (GAS) 75,76 methods. In addition to this, several approximate full CI (FCI) methods have recently been developed and integrated into CASSCF, as for example the FCI quantum Monte Carlo (FCIQMC) method, [77][78][79] the heat-bath CI, [80][81][82] or the density matrix renormalization group (DMRG) methods.…”

Section: Introductionmentioning

confidence: 99%

MCSCF optimization revisited. II. Combined first- and second-order orbital optimization for large molecules

Kreplin

Knowles

Werner

2020

The Journal of Chemical Physics

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A new orbital optimization for the multiconfiguration self-consistent field (MCSCF) method is presented. This method combines a second-order (SO) algorithm for the optimization of the active orbitals with the first-order Super-CI (SCI) optimization of the remaining closed-virtual rotations and is denoted as SO-SCI method. The SO-SCI method improves the convergence significantly as compared to the conventional SCI method. In combination with density fitting, the intermediates from the gradient calculation can be reused to evaluate the two-electron integrals required for the active Hessian without introducing a large computational overhead. The orbitals and configuration interaction (CI) coefficients are optimized alternately, but the CI-orbital coupling is accounted for by the Limited Memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) quasi-Newton method. This further improves the speed of convergence. The method is applicable to large molecules. The efficiency and robustness of the presented method is demonstrated in benchmark calculations for 21 aromatic molecules as well as for various transition metal complexes with up to 826 electrons and 5154 basis functions.

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Section: Introductionmentioning

confidence: 99%

MCSCF optimization revisited. II. Combined first- and second-order orbital optimization for large molecules

Kreplin

Knowles

Werner

2020

The Journal of Chemical Physics

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“…However, due to the exponential scaling of FCI, it is limited to small complete active spaces (CAS), usually no more than CAS (16,16) (16 electrons in 16 orbitals). However, there are now several techniques which can be used to replace the FCI solver [19,20,21,22,23,24]. Two of the more commonly used ones are the density matrix renormalization group (DMRG) [19] and full configuration interaction quantum Monte Carlo (FCIQMC) [21,22].…”

Section: Introductionmentioning

confidence: 99%

A general second order complete active space self-consistent-field solver for large-scale systems

Sun

Yang

Chan

2017

Chemical Physics Letters

122

146

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We present a new second order complete active space self-consistent field implementation to converge wavefunctions for both large active spaces and large atomic orbital (AO) bases. Our algorithm decouples the active space wavefunction solver from the orbital optimization in the microiterations, and thus may be easily combined with various modern active space solvers. We also introduce efficient approximate orbital gradient and Hessian updates, and step size determination. We demonstrate its capabilities by calculating the low-lying states of the Fe(II)-porphine complex with modest resources using a density matrix renormalization group solver in a CAS(22,27) active space and a 3000 AO basis.

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“…Therefore, it will be necessary to consider other solutions to optimize the orbitals, the first step of the CAS+DDCI+Q calculations. A promising solution that we are investigating on capped peptides containing at least two residues is given by the Generalized Active Space Self Consistent Field (GASSCF) method, 53,54 a method which allows us to expand active spaces beyond the CASSCF limit. This work will be reported in a future paper.…”

Section: Discussionmentioning

confidence: 99%

Low-lying excited states of model proteins: Performances of the CC2 method versus multireference methods

Amor

Hoyau

Maynau

et al. 2018

The Journal of Chemical Physics

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A benchmark set of relevant geometries of a model protein, the N-acetylphenylalanylamide, is presented to assess the validity of the approximate second-order coupled cluster (CC2) method in studying low-lying excited states of such bio-relevant systems. The studies comprise investigations of basis-set dependence as well as comparison with two multireference methods, the multistate complete active space 2nd order perturbation theory (MS-CASPT2) and the multireference difference dedicated configuration interaction (DDCI) methods. First of all, the applicability and the accuracy of the quasi-linear multireference difference dedicated configuration interaction method have been demonstrated on bio-relevant systems by comparison with the results obtained by the standard MS-CASPT2. Second, both the nature and excitation energy of the first low-lying excited state obtained at the CC2 level are very close to the Davidson corrected CAS+DDCI ones, the mean absolute deviation on the excitation energy being equal to 0.1 eV with a maximum of less than 0.2 eV. Finally, for the following low-lying excited states, if the nature is always well reproduced at the CC2 level, the differences on excitation energies become more important and can depend on the geometry.

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Systematic Expansion of Active Spaces beyond the CASSCF Limit: A GASSCF/SplitGAS Benchmark Study

Cited by 57 publications

References 87 publications

MCSCF optimization revisited. II. Combined first- and second-order orbital optimization for large molecules

MCSCF optimization revisited. II. Combined first- and second-order orbital optimization for large molecules

A general second order complete active space self-consistent-field solver for large-scale systems

Low-lying excited states of model proteins: Performances of the CC2 method versus multireference methods

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