New Formulation and Implementation of Vibrational Self-Consistent Field Theory

Hansen, Mikkel Bo; Sparta, Manuel; Seidler, Peter; Toffoli, Daniele; Christiansen, Ove

doi:10.1021/ct9004454

Cited by 74 publications

(130 citation statements)

References 33 publications

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“…As an example, we consider ∆p f k for f k = {A, B}, with k = 2, in the above example, where {A, B, C, D} was added to the FCR 3F,NB in Eq. (25). The size of the largest added fragment combination is, hence, l = 4.…”

Section: Summary Conclusion and Outlookmentioning

confidence: 99%

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Linear-scaling generation of potential energy surfaces using a double incremental expansion

König

Christiansen

2016

The Journal of Chemical Physics

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We present a combination of the incremental expansion of potential energy surfaces (PESs), known as n-mode expansion, with the incremental evaluation of the electronic energy in a many-body approach. The application of semi-local coordinates in this context allows the generation of PESs in a very cost-efficient way. For this, we employ the recently introduced flexible adaptation of local coordinates of nuclei (FALCON) coordinates. By introducing an additional transformation step, concerning only a fraction of the vibrational degrees of freedom, we can achieve linear scaling of the accumulated cost of the single point calculations required in the PES generation. Numerical examples of these double incremental approaches for oligo-phenyl examplesshow fast convergence with respect to the maximum number of simultaneously treated fragments and only a modest error introduced by the additional transformation step.The approach, presented here, represents a major step towards the applicability of vibrational wave function methods to sizable, covalently bound systems. a) Electronic mail: carolink@kth.se; Present address: KTH Royal

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Section: Summary Conclusion and Outlookmentioning

confidence: 99%

“…In special cases, effective linear scaling of the number of required SPCs has been observed with an adaptive grid approach 25 . Both screening as well as adapted choice of required grid points are expected to be particularly beneficial, when combined with adapted coordinates with some kind of spatial locality [26][27][28][29] .…”

Section: Introductionmentioning

confidence: 99%

Linear-scaling generation of potential energy surfaces using a double incremental expansion

König

Christiansen

2016

The Journal of Chemical Physics

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“…The main difference lies in the number of mode combinations: For the water dimer, we compare to VCC [6] (=full VCI for the current model) containing 63 mode combinations. We, hence, include mode combinations outside the mode combination range of the operator in this case.…”

Section: A Importance and Measures Of Mode Combinationsmentioning

confidence: 99%

“…6 For unambiguous interpretation of vibrational spectra, however, it will often be necessary to go beyond the VSCF mean field description. Using VSCF as a reference, we will formulate different estimates for the importance of different mode-mode correlations in the wave function calculation for a given Hamiltonian.…”

Section: Introductionmentioning

confidence: 99%

“…or screened with Hamiltonian (hs), first-order perturbative (p1s), or scaled second-order perturbative measures (p2s) for the water dimer (left) and water trimer (middle) for VCC[6,measure = 10 −X ], and the water hexamer (right) for VCC[5,measure = 10 −X ]. The integer X denotes either the maximal mode-combination level in the hierarchical scheme or the threshold (10 −X , X = 2, 3, 4,[5],[6]) for the screening measures. Different levels of mode combinations (MC) are distinguished.…”

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Automatic determination of important mode–mode correlations in many-mode vibrational wave functions

König

Christiansen

2015

The Journal of Chemical Physics

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We introduce new automatic procedures for parameterizing vibrational coupled cluster (VCC) and vibrational configuration interaction wave functions. Importance measures for individual mode combinations in the wave function are derived based on upper bounds to Hamiltonian matrix elements and/or the size of perturbative corrections derived in the framework of VCC. With a threshold, this enables an automatic, system-adapted way of choosing which mode-mode correlations are explicitly parameterized in the many-mode wave function. The effect of different importance measures and thresholds is investigated for zero-point energies and infrared spectra for formaldehyde and furan. Furthermore, the direct link between important mode-mode correlations and coordinates is illustrated employing water clusters as examples: Using optimized coordinates, a larger number of mode combinations can be neglected in the correlated many-mode vibrational wave function than with normal coordinates for the same accuracy. Moreover, the fraction of important mode-mode correlations compared to the total number of correlations decreases with system size. This underlines the potential gain in efficiency when using optimized coordinates in combination with a flexible scheme for choosing the mode-mode correlations included in the parameterization of the correlated many-mode vibrational wave function. All in all, it is found that the introduced schemes for parameterizing correlated many-mode vibrational wave functions lead to at least as systematic and accurate calculations as those using more standard and straightforward excitation level definitions. This new way of defining approximate calculations offers potential for future calculations on larger systems.

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Perspectives of quantum computing for chemical engineering

et al. 2022

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Quantum computing has been attracting public attention recently. This interest is driven by the advancements in hardware, software, and algorithms required for its successful usage and the promise that it entails the potential acceleration of computational tasks compared to classical computing. This perspective article presents a short review on quantum computing, how this computational approach solves problems, and three fields that quantum computing can potentially impact the most while relevant to chemical engineering: computational chemistry, optimization, and machine learning. Here, we present a series of chemical engineering applications, the developments, potential improvements with respect to classical computing, and challenges that quantum computing faces for each of these fields. This article intends to provide a clear picture of the challenges and potential advantages that quantum technology may yield for chemical engineering, together with an invitation for our colleagues to join us in the adoption and development of quantum computing.

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New Formulation and Implementation of Vibrational Self-Consistent Field Theory

Cited by 74 publications

References 33 publications

Linear-scaling generation of potential energy surfaces using a double incremental expansion

Linear-scaling generation of potential energy surfaces using a double incremental expansion

Automatic determination of important mode–mode correlations in many-mode vibrational wave functions

Perspectives of quantum computing for chemical engineering

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