Approaches to Materials Discovery in Inorganic Solid State Chemistry

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Inorganic solids form the basis of many of today's technological applications. How do metals and metalloids combine to form these new solids (called “intermetallic compounds”)? Surprisingly, it is still not easy to predict how elements (especially metals) react with each other, what structures they adopt, and what physical properties they possess. For some specific solids, chemists have been successful in applying strategies to “design” new compounds, such as manipulating building blocks or identifying missing members within related series. Because these strategies rely on precedent, by definition, they cannot foresee surprising or counterintuitive results. Exploratory work is essential for expanding our knowledge base. Experimental methods include high-temperature reactions (up to 1000 C), X-ray diffraction, spectroscopy, physical property measurements, and quantum calculations. Students trained in these diverse skills, which lie at the interface of chemistry, physics, and materials science, are well suited for careers in advanced materials research. As relationships between compositions, structures, and properties grow more complex, eventually the pattern recognition skills become too difficult for humans to handle. To complement these traditional approaches, we propose that machine-learning methods may serve as an alternative approach to discover new materials, more reliably and much faster. Using both these approaches, we will synthesize new compounds of various metals and borderline metalloids (such as germanium, arsenic, and selenium). Building on our past interest in developing thermoelectric materials, which can convert waste heat to electricity, we have several exciting new applications in mind for compounds to be targeted. First, we want to evaluate various arsenides as potential host structures in which small amounts of magnetic atoms can be added to give rise to ferromagnetic semiconductors, which could be used in spintronic devices to build much more powerful computers. Second, we are designing selenides and related compounds with special structures so that they can be used as nonlinear optical materials to fabricate infrared lasers for sensing explosives or performing selective surgical procedures. Third, we want to discover new coloured intermetallics, which are exceedingly rare but are highly valued because of their beauty. All of these applications have the potential to significantly impact many sectors, such as energy, information technology, environmental sustainability, and defense, which are of vital interest to Canada. Our broader vision is that these approaches can be generalized to other types of materials so that scientists can combine the wisdom of humans and the speed of machines to gain a deeper understanding of nature, to unravel the hidden relationships between structures and properties, and to accelerate materials discovery.