by: Dr. David Ginley, Research Fellow/ Chief Scientist, Materials and Chemistry Science and Technology, National Renewable Energy Laboratory (NREL), USA.
Historically theory has been employed to explain experimental observations, more recently this has been inverted with the prediction of new functional materials computationally followed by their experimental realization. Most of these materials are at the bottom of the convex hull i.e. in thermodynamic equilibrium. However, many functional materials are actually employed well above the hull, i.e. they are metastable. We will discuss our recent work to begin to address predictive computations for a number of kinds of metastability and their experimental realization. One class is polymorphic systems where higher energy polymorphs have both significant structural and functional differences than the ground state materials. Examples are the TiO2 system where rutile is the ground state but anatase is a better electronic material and brookite is a better catalyst. A second class is alloy systems such as ZnMnOx where it is possible to force the correct functional phases to get better functionality such as photo-electrochemical water splitting. A third class is control of the defects/doping of semiconductor materials such as transparent conductive oxides like Ga2O3 where functionality depends on controlling the eliminating deleterious defects and enhancing the density of beneficial ones. We will discuss recent computational results and the experimental exploration of the computational predicted metastable materials that directly affect energy conversion.
This work was funded by the Center for the Next Generation of Materials by Design, an
Energy Frontier Research Center funded by the U.S. Department of Energy, Office of
Science, Basic Energy Sciences under Contract No. DE-AC36-08GO28308 to NREL.
Authors: David Ginley1, Gebrand Ceder2, Kristin Persson2, Mike Toney3, Stephan Lany1, and William Tumas1
1 National Renewable Energy Laboratory, Golden, CO 80401
2 Lawrence Berkeley National Labortory, Berkeley CA
3 SLAC National Accelerator Laboratory, Palo Alto CA