Ab initio thermodynamics of liquid and solid water

Cheng, Bingqing; Engel, Edgar A.; Behler, Jörg; Dellago, Christoph; Ceriotti, Michele

doi:10.1073/pnas.1815117116

Cited by 294 publications

(362 citation statements)

References 66 publications

(81 reference statements)

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“…As described throughout this work, this improved electronic structure is not sufficient to provide a quantitative description of the structural properties of liquid water, and there is still room for further improvement. At the level of vdW-inclusive hybrid DFT, the revPBE0-D3 functional [21,22,27,28] appears to predict a g OO (r) in better overall agreement with experiment [29]. However, that functional predicts smaller NQEs than PBE0-TS; for example, the differences between the classical and quantum RDFs for H 2 O reported in Ref.…”

Section: Potential Improvement and Future Outlookmentioning

confidence: 71%

Isotope effects in liquid water via deep potential molecular dynamics

Zhang

Santra

et al. 2019

Molecular Physics

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A comprehensive microscopic understanding of ambient liquid water is a major challenge for ab initio simulations as it simultaneously requires an accurate quantum mechanical description of the underlying potential energy surface (PES) as well as extensive sampling of configuration space. Due to the presence of light atoms (e.g., H or D), nuclear quantum fluctuations lead to observable changes in the structural properties of liquid water (e.g., isotope effects), and therefore provide yet another challenge for ab initio approaches. In this work, we demonstrate that the combination of dispersion-inclusive hybrid density functional theory (DFT), the Feynman discretized path-integral (PI) approach, and machine learning (ML) constitutes a versatile ab initio based framework that enables extensive sampling of both thermal and nuclear quantum fluctuations on a quite accurate underlying PES. In particular, we employ the recently developed deep potential molecular dynamics (DPMD) model-a neural-network representation of the ab initio PES-in conjunction with a PI approach based on the generalized Langevin equation (PIGLET) to investigate how isotope effects influence the structural properties of ambient liquid H2O and D2O. Through a detailed analysis of the interference differential cross sections as well as several radial and angular distribution functions, we demonstrate that this approach can furnish a semi-quantitative prediction of these subtle isotope effects.

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Section: Potential Improvement and Future Outlookmentioning

confidence: 71%

Isotope effects in liquid water via deep potential molecular dynamics

Zhang

Santra

et al. 2019

Molecular Physics

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“…This "human-learning" method is sufficient for this simple three-body potential; machinelearning strategies would also be possible. [13][14][15] To illustrate the structure of the three-body potential, Fig. 7 shows the energy of the (2+3)-body coarse The effective interaction in this three-particle system is shown with symbols (FG) in (a), calculated by Jarzynski integration.…”

Section: Appendix C: Coarse Model With Three-body Interactionsmentioning

confidence: 99%

“…It shares many features with importance sampling methods, biased sampling techniques, 22,23 and free-energy perturbation methods 24 (see for example Ref. 15 for a recent application of this method, in order to correct for coarse-graining errors). Our implementation of the TL method is informed by recent mathematical results and has been chosen to minimise the systematic errors (bias) in our estimates of properties of the FG system.…”

Section: Introductionmentioning

confidence: 99%

Correction of coarse-graining errors by a two-level method: Application to the Asakura-Oosawa model

Kobayashi

Rohrbach

Scheichl

et al. 2019

The Journal of Chemical Physics

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We present a method that exploits self-consistent simulation of coarse-grained and fine-grained models, in order to analyse properties of physical systems. The method uses the coarse-grained model to obtain a first estimate of the quantity of interest, before computing a correction by analysing properties of the fine system. We illustrate the method by applying it to the Asakura-Oosawa (AO) model of colloid-polymer mixtures. We show that the liquid-vapour critical point in that system is affected by three-body interactions which are neglected in the corresponding coarse-grained model. We analyse the size of this effect and the nature of the three-body interactions. We also analyse the accuracy of the method, as a function of the associated computational effort. arXiv:1907.07912v1 [cond-mat.stat-mech]

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“…In the first stepρ scp (r) are those obtained within the harmonic approximation. In the second loop we calculate the ensemble averages of the forces and the Hessian, necessary to perform the optimization steps described in equation 26. These are realized as Gaussian integrals and computed using MC importance sampling as…”

Section: Self-consistent Phononsmentioning

confidence: 99%

“…14 The problem is exacerbated for the case of organic solids, which require a proper description of anharmonicity arising from quantum nuclear motion even at room temperature. [15][16][17][18] This is similarly true for (i) systems containing light elements, such as hydrogen, [19][20][21] helium 22 and water, 23 ice, [24][25][26] metal organic frameworks , 27,28 the record high-T c conventional superconductor SH 3 , 29 (ii) systems of reduced effective dimensionality such as graphene 30,31 and (iii) molecular systems such as paracetamol. 18 Within the BO approximation 32 and given the BO potential, exact anharmonic free energies can be calculated using approaches based on imaginary time path integral (PI) simulations.…”

Section: Introductionmentioning

confidence: 99%

Assessment of Approximate Methods for Anharmonic Free Energies

Kapil

Engel

Rossi

et al. 2019

J. Chem. Theory Comput.

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Quantitative evaluations of the thermodynamic properties of materials -most notably their stability, as measured by the free energy -must take into account the role of thermal and zero-point energy fluctuations. While these effects can easily be estimated within a harmonic approximation, corrections arising from the anharmonic nature of the interatomic potential are often crucial and require computationally costly path integral simulations. Consequently, different approximate frameworks for computing affordable estimates of the anharmonic free energies have been developed over the years. Understanding which of the approximations involved are justified for a given system, and therefore choosing the most suitable method, is complicated by the lack of comparative benchmarks. To facilitate this choice we assess the accuracy and efficiency of some of the most commonly used approximate methods -the independent mode framework, the vibrational self-consistent field and self-consistent phonons -by comparing the anharmonic correction to the Helmholtz free energy against reference path integral calculations. These benchmarks are performed for a diverse set of systems, ranging from simple quasi-harmonic solids to flexible molecular crystals with freely-rotating units. Our results suggest that for simple solids such as allotropes of carbon these methods yield results that are in excellent agreement with the reference calculations, at a considerably lower computational cost. For more complex molecular systems such as polymorphs of ice and paracetamol the methods do not consistently provide a reliable approximation of the anharmonic correction. Despite substantial cancellation of errors when comparing the stability of different phases, we do not observe a systematic improvement over the harmonic approximation even for relative free-energies. Our results suggest that efforts towards obtaining computationallyfeasible anharmonic free-energies for flexible molecular solids should therefore be directed towards reducing the expense of path integral methods.

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Ab initio thermodynamics of liquid and solid water

Cited by 294 publications

References 66 publications

Isotope effects in liquid water via deep potential molecular dynamics

Isotope effects in liquid water via deep potential molecular dynamics

Correction of coarse-graining errors by a two-level method: Application to the Asakura-Oosawa model

Assessment of Approximate Methods for Anharmonic Free Energies

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