Materials Science Research Lecture

Abstract:

A large number of low-energy, metastable states lie slightly above the tie lines that connect thermodynamically stable points on the convex hull. Thus, for any particular system, it is statistically probable that a specific property exhibited by the ground-state structure is not the optimal one that is possible. It is therefore desirable to develop strategies for the synthesis of metastable materials, which may have alternative properties from the ground state. High pressure is an effective tool to access such new materials. Multiple allotropes and/or chemical compounds may be formed under high-pressure conditions, and some of these remain metastable under standard conditions with prospects for future applications. Here we provide an overview of how pressure can be used to create new materials. In particular, we present recent progress in the synthesis of "exotic" forms of silicon with improved optical and electronic properties when compared with the normal, diamond-structured counterpart. We describe a new class of diamond-like sp3 carbon-based clathrate materials comprised of truncated octahedral cages that trap metal atoms and provide tunable electronic structures. Finally, we present a computational framework for phase transition pathways that can be used to help guide synthesis, from precursor to product.

More about the Speaker:

Timothy (Tim) was born in Boulder, CO. With ambitions of becoming a pyrotechnics engineer, he set off to the Colorado School of Mines after graduating high school. This particular field of study was not offered in the curriculum, so he settled for the closest major (Chemical Engineering) and obtained a B.S. in 2004. Staying on at Mines for a Ph.D. (2008), he studied gas hydrates with Prof. E. Dendy Sloan where he developed a passion for novel energy materials, molecular compounds, thermodynamics and spectroscopy.

In 2008 Tim joined the Geophysical Laboratory of the Carnegie Institution of Washington as a Carnegie Postdoctoral Fellow. During his postdoc he became fascinated by high-pressure science. In 2010 he was appointed Research Scientist, then Staff Scientist in 2011. He is trying to make new materials with advanced properties using high- pressure techniques.