Developing and applying machine learning approaches to understand water at interfaces

Lead Research Organisation: University College London
Department Name: London Centre for Nanotechnology

Abstract

Brief description of the context of the research including potential impact;
This project will focus on the development of highly accurate water potentials at interfaces and on surfaces using machine learning approaches. Research is continually hampered by having to make the tradeoff between accuracy and speed, should an investigation into a particular problem make use of classical force field molecular dynamics, or does the nature of the problem warrant the greater accuracy of ab initio methods?

Aims and objectives
Despite the familiarity of this question to many researchers, there is no fundamental reason why classical MD cannot attain the same accuracy that ab initio methods have; it is the aim of this project to design a force field capable of providing this accuracy. A highly accurate molecular dynamics potential would facilitate the study of large ensembles of molecules while maintaining the accuracy of the underlying ab initio training data. The usefulness of such a capability would be immediately obvious, for example in understanding the behavior of water under confinement, in developing nanoporous water filters and in understanding the processes of ice nucleation and crystal growth.

Novelty of the research methodology
Machine learning techniques have grown in popularity in recent years in a wide variety of fields due to their unique power in unravelling complex multidimensional problems. While they have been applied to the development of molecular force fields before, previous research has focused largely upon the bulk material. In applying this methodology to an interfacial system (e.g. water on carbon) this research will both push the boundaries of the current state-of-the art and produce an end 'product' which has a vastly more widespread applicability; interfaces being generally more interesting from a research perspective than the bulk.

Alignment to EPSRC's strategies and research areas
The wider impact of this research would be felt across many branches of the EPSRCs portfolio, it is challenging to conceive of a field which would not benefit hugely from development of highly accurate molecular dynamics force fields. There would be applications in medicine (biosensor development, understanding of fundamental biological processes, drug development), engineering (highly selective filtration, corrosion processes, materials development) etc.

Any companies or collaborators involved
This research is currently being conducted in collaboration with Gabór Csányi at the university of Cambridge, and Laurent Joly of Université Lyon.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509577/1 01/10/2016 24/03/2022
1782307 Studentship EP/N509577/1 01/10/2016 30/12/2020 Patrick Rowe
 
Description In the past there have been two available methodologies for simulating the atomic-scale dynamical behaviour of materials in computers - using classical molecular dynamics where atoms are approximated as hard spheres interacting with fixed interactions - which lacks accuracy, and using ab initio molcular dynamics where forces are computed on the fly from quantum mechanics - which is extremely expensive. Machine learning approaches have arisen recently as a way of obtaining quantum mechanical accuracy with the cost of classical molecular dynamics. We have shown for the first time that the accuracy of a machine learning potential can be high enough that the results are functionally identical to those from direct ab initio evaluation. Further, we have extended our work on pure graphene to produce a machine learning model which is accurate for a wide range of relevant phases for carbon, which maintains accuracy on the crystalline phases while simultaneously being flexible enough to treat liquid and amorphous structures.
Exploitation Route database used for training made publicly and freely available, code used to train potential made publicly available, anyone can download and continue this work.
Sectors Aerospace, Defence and Marine,Chemicals,Digital/Communication/Information Technologies (including Software),Energy

URL https://journals.aps.org/prb/abstract/10.1103/PhysRevB.97.054303
 
Title Database of Graphene Structures and Quantum Mechanical Forces 
Description As part of a publication: Development of a machine learning potential for graphene, we made available free of charge a database of several thousand structures of graphene, with the associated physical properties (energies, forces..) calculated from density functional theory. Such a database is suitable for use in applications such as machine learning. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
Impact N/a 
URL http://www.libatoms.org/pub/Home/DataRepository/graphene_gap_final.tar.gz
 
Title Machine Learning Potential for Graphene 
Description This GAP model obtains a faithful representation of a density functional theory (DFT) potential energy surface, facilitating highly accurate (approaching the accuracy of ab initio methods) molecular dynamics simulations. This is achieved at a computational cost which is orders of magnitude lower than that of comparable calculations which directly invoke electronic structure methods. 
Type Of Material Computer model/algorithm 
Year Produced 2018 
Provided To Others? Yes  
Impact Demonstrated the potential accuracy of machine learning models, helped to encourage further research 
URL http://www.libatoms.org/pub/Home/DataRepository/graphene_gap_final.tar.gz