Mapping Uncharted chemical spaces

Dr. Wenhao Sun

There is something deeply human about exploration. Within each of us, there is a great curiosity to venture into the unknown—to discover something new. There is an unfortunate quote about our generation, which says, “We are the middle children of history. Born too late to explore the earth, born too early to explore the stars.” But actually, there is still a new frontier being explored today—-chemical space.

Now, chemical space is not really a physical place; meaning we can't sail to it like we would to a new island or continent. Instead, we explore chemical space in a laboratory--mixing new combinations of elements together in a reactor. Sometimes, if we're lucky, these elements will react together to form a new compound. Every one in this room has benefitted from the discovery of new compounds; these new materials form the basis of safer cars, lighter airplanes, faster computers and longer-lasting cell phones.

Which elements will react together to form a new compound? Actually, it is not so easy to say. We have some ideas and principles to guide us, but they're not perfect. For this reason, chemical exploration is a very risky endeavor.

Using modern methods of computational materials science, we can now calculate if a new material will be stable, and therefore synthesizable, without even stepping foot in a lab.

Here at LBNL, I use powerful supercomputers to search through thousands of hypothetical compounds for new stable materials. Just as ancient maps were used to guide explorers to new lands, we can construct stability maps to guide chemists in their exploratory synthesis of new compounds.

Here, I am showing a large stability map for the ternary metal nitrides; an important but rare class of materials. A ternary nitride is made up of three elements, Metal 1, Metal 2, and Nitrogen. On this map, the rows are Metal 1 and the columns are Metal 2, so each square represents a potential ternary nitride compound. On this stability map, blue means that that ternary nitride is stable. Green means that nitride can be perhaps stabilized under under special conditions. And red means that that nitride is unstable, and probably cannot be made.

Only 25% of the spaces on this map are blue, meaning if I were to randomly mix elements with nitrogen (basically throwing darts at this map) I'd have about a 25% chance of successful nitride synthesis. However, guided by this map, my experimental colleagues have already made 10 out of 10 new nitrides that they've tried; a 100% hit rate. :D

Beyond the nitrides, there remain many other chemical spaces awaiting discovery. Our approach here can be used to further map these uncharted chemical spaces—providing chemists guidance in their quest to extend the frontier of solid-state chemistry.

Thank you very much