Dielectric Constant of Liquid Water Determined with Neural Network Quantum Molecular Dynamics

The static dielectric constant ϵ0 and its temperature dependence for liquid water is investigated using neural network quantum molecular dynamics (NNQMD). We compute the exact dielectric constant in canonical ensemble from NNQMD trajectories using fluctuations in macroscopic polarization computed fr...

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Bibliographic Details
Published in:Physical review letters 2021-05, Vol.126 (21), p.216403-216403, Article 216403
Main Authors: Krishnamoorthy, Aravind, Nomura, Ken-ichi, Baradwaj, Nitish, Shimamura, Kohei, Rajak, Pankaj, Mishra, Ankit, Fukushima, Shogo, Shimojo, Fuyuki, Kalia, Rajiv, Nakano, Aiichiro, Vashishta, Priya
Format: Article
Language:English
Subjects:
Artificial neural networks
Computation
Configurations
Molecular dynamics
Neural networks
Permittivity
Polarization
Potential energy
Temperature dependence
Water
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Summary:The static dielectric constant ϵ0 and its temperature dependence for liquid water is investigated using neural network quantum molecular dynamics (NNQMD). We compute the exact dielectric constant in canonical ensemble from NNQMD trajectories using fluctuations in macroscopic polarization computed from maximally localized Wannier functions (MLWF). Two deep neural networks are constructed. The first, NNQMD, is trained on QMD configurations for liquid water under a variety of temperature and density conditions to learn potential energy surface and forces and then perform molecular dynamics simulations. The second network, NNMLWF, is trained to predict locations of MLWF of individual molecules using the atomic configurations from NNQMD. Training data for both the neural networks is produced using a highly accurate quantum-mechanical method, DFT-SCAN that yields an excellent description of liquid water. We produce 280 × 106 configurations of water at 7 temperatures using NNQMD and predict MLWF centers using NNMLWF to compute the polarization fluctuations. The length of trajectories needed for a converged value of the dielectric constant at 0 °C is found to be 20 ns ( 40 × 106 configurations with 0.5 fs time step). The computed dielectric constants for 0, 15, 30, 45, 60, 75, and 90 °C are in good agreement with experiments. Our scalable scheme to compute dielectric constants with quantum accuracy is also applicable to other polar molecular liquids.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.126.216403