Materials Epigenetics

Materials epigeneticsJust a few years back, the thought of synthesising a perfect material that can completely convert solar energy to electrical energy, or a material able to split water molecules to release hydrogen and oxygen gas that is very efficient and very cheap would have seemed like a far-fetched idea from a science fiction movie.

Today, hundreds of chemists, physicists and materials scientists are fully engaged in searching for such novel functional materials that are environmentally friendly, abundant and cheap to fabricate. Naively thinking one might want to start by combining all elements from the periodic table to form compounds and then test them one by one, keeping only those that meet certain criteria. The 98 naturally occurring elements can be combined in pairs to form 4753 possible compounds (binary compounds). The number rises to 152096 compounds for ternary combinations, and 3612280 compounds for quaternary combinations. This huge combinations assume elements are added in equal ratio and do not include the fact that many compounds show a deviation from perfect stoichiometry. Some estimates go as far as predicting the number of possible compounds as 10100.This will immediately discard the possibility of experimentally testing and characterising each and every compound.

Here, the role of computer simulations becomes apparent. With the exponential increase in computational power and progressive dissemination of such computing capability to the researcher’s desktop, it is becoming more and more routine to calculate electronic structure of compounds and to infer or predict important properties from the band structure and related descriptors. Researchers can predict new crystal structures with certain properties which are passed to experimentalist who can test and verify the predictions.

In recognition of the great potential of computational modelling to advance and accelerate materials design and development, the Materials Genome Initiative2 is one of the two major research thrust areas in the US that are slated for large scale support in the next 5-10 years. Similar initiatives are underway in Europe and in China. It is based on the concept of accelerated materials discovery using high throughput computational prediction and screening of crystal structures based on generic descriptors (energy, band-gap, etc.) and building protocols for universally accessible databases that can store the valuable results of such calculations. Beyond this simple starting concept, it has always been apparent that material properties and function for the vast diversity of applications are not dictated by a simple “genetic code” based on ideal crystal structures. In fact, materials function is most often mediated by departures from the perfect structure – vacancies, chemical dopants, edges, chemical functionalisations, imperfect or incomplete self-assembly, metastable morphologies and other types of defects. Further, the interaction of the material with different components of an overall device or system – hybrid interfaces, electric fields or applied voltages, contacts, designed or serendipitous nanoscale architecture and so forth – impact significantly on overall system performance. Hence, even more than in biology - from which the “genome” terminology is borrowed – an epigenetics approach to materials discovery and design that computationally explores material properties beyond ideal structures will be crucial in order to truly aid in the accelerated development of functional materials and technologies. This agenda is encapsulated in the term Materials Epigenetics.

The Integrated Materials Design Centre (IMDC) pursues the materials epigenetics agenda. The IMDC’s core business is theory and computation. It’s core philosophy is to pursue a holistic approach to the materials design cycle involving a tight collaborative exchange between the key “moving parts” of the materials discovery process: synthesis; characterization; testing and modelling. To this end, we have developed a structure that includes our core centre members who are heavily engaged in theory and modelling as well as key and valued experimental collaborators whose complementary expertise helps to instantiate this collaborative vision.

Being able to explore and apply materials epigenetics in tight collaboration with our experimental colleagues will allow us to truly fire the afterburners in the materials design process. It will lead to new material and system functionalities, limited only by one’s imagination. 

  1. A. Walsh, Nature Chemistry 7, 274–275 (2015)