1. Formula graph self-attention network for materials discovery (Finder)

finder-architecture
Machine learning (ML) has entered materials science arena as a fast and accurate tool for materials property prediction. Such ML models expect materials to be represented in numeric format (vector or array), also known as the material representation or descriptor. Two types of material descriptors exists, one that encodes crystal structure details for and the other that only uses chemical composition information with the hope of representing hypothetical compositions and discovering new ones. Recently, graph neural networks (GNNs) have shown excellent performance in predicting materials properties, typically outperforming classical ML algorithms. In this project, I developed a novel GNN architecture (named Finder) that integrates self-attention mechanism for predicting the properies of materials using their chemical composition or crystal structure. The proposed model displayed better performance, faster convergence and better domain transferability compared to some other state-of-the-art GNNs on materials benchmark datasets. Finder is listed as a high performer on Matbench benchmark suite leaderboard maintained by Bekerley Lab, USA.

2. Analogical materials discovery (Analogmat)

analogmat-architecture
Material fingerprinting allows to quantify materials analogies by computing a distance metric between fingerprint vectors. In this project, I developed an unsupervised variational autoencoder (VAE) to extract the fingerprint (latent embedding) of perovskite-oxide type materials. Such materials have a broad range of applications including photovoltaics, tunable devices, solid oxide fuel cells, etc. However, many industrial materials contain the element lead (Pb), causing hazards and environmental issues. Here, I found that ML-derived material fingerprints can be applied to discover eco-friendly sustainable alternatives to Pb-based industrial ceramics.

3. Open Database of Dielectric Ceramics (ODDC)

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This is an ongoing project that involves developing a comprehensive experimental database of dielectric ceramic materials and their properties (e.g., dielectric constant, Q-factor, TCF). Currently, such data is dispersed over the literature and a centralised repository for dielectric materials especially over a wide measurement frequency range (1kHz - 10GHz) does not exist. Here, I apply Natural Language Processing (NLP) tools and ChemDataExtractor package to automatically extract data from literature and the database will be hosted online with free and open source access. A standalone version of the Finder ML model will be integrated to the web interface for convienient prediction of material properties, which can particularly be useful to the researchers outside of the field of ML.

4. AIMat software for predicting microwave properties of dielectrics (AIMat)

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The objective of this project is to predict the dielectric constant, Quality factor (1/loss tangent) and the temperature coefficient of resonance frequency of (1-x)A - xB type alloyed compositions where A and B are two known dielectric materials and x is the mole fraction of B. Such materials can be intruguing candidates for 5G resonators. Predictions are made by three inter-dependent deep neural networks. 5G materials require a high quality factor (low loss) and moderate dielectric constant (around 5), and a temperature coefficient near zero. A user friendly software is developed so interested researchers can choose constituent materials from hundreds of available materials in our database and get an idea of how the properties will look like when the selected two materials are mixed at a given ratio. Additionally, users can set target properties and apply genetic algorithm optimisation provided in the repository to inversely discover new materials that fit their purpose.

5. Reinforcement learning for coding metasurface optimisation (MetaZero)

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Metasurfaces are artificial composite materials with subwavelength thickness. They are made by arranging unit cells (aka coding elements) of different shapes and sizes in a grid-like structure. Metasurfaces can be used to manipulate electromagnetic waves by configuring the location of coding elements. In this project, the objective is to minimise the Radar Cross Section (RCS) of a coding metasurface. For instance, the surface of military aircrafts may be fabricated using a metasurface with very low RCS so they are less detectable by radar signals. Here, three types of coding elements with phase response pi/4, pi/2 and pi are used. The problem is mapped to a 3-player game where each player trys to make a move, that means placing their coding element on the metasurface grid, such that the overall RCS is minimised. I used reinforcement learning with monte carlo tree search to optimise the coding sequence, inspired by AlphaZero algorithm by DeepMind. It can be seen from the demo above that the RCS is generally reducing after each move. The game terminates once the whole grid is filled.