Physics Colloquium: Exploring the chemical landscape of functional oxides using theory and computation – Dr. Valentino Cooper (Oak Ridge National Laboratory)

Dr. Valentino Cooper, Oak Ridge National Laboratory

Abstract: High entropy, multi-component metal alloys (HEA), have superior mechanical properties and high radiation tolerances; which are, in part, driven by configurational entropy. Recently, an oxide analogue comprised of MgO, CoO, NiO, CuO and ZnO was synthesized; exhibiting a truly entropy-stabilized, reversible phase transition from a multiphase material to a single rock salt-ordered phase above 850-900°C. This entropy-driven stabilization may engender many unique properties, such as high melting temperatures, radiation resistance and other anomalous responses. Here, we discuss a design strategy for the prediction of synthesizable disordered oxides. Our effort employs first principles studies of 2-component oxides to develop design rules based on the relationship between pairwise enthalpies of formation, ΔH, and configurational entropy of the disordered material. A similar chemical identity-to-ΔH map was previously explored using the class of high entropy alloys, where the stability of multicomponent metal alloys was correlated to the enthalpy of mixing of binary and ternary compounds.
In this presentation, I will focus on our recent efforts to employ this local enthalpy map as an effective strategy for the discovery of new classes of entropy stabilized oxides. In particular, we are able to use our first principles calculations with Monte Carlo simulations in order to build chemical bonding maps to study the local environment preferences that determine whether a material will phase segregate, to form a single phase with clustered regions, or form a disordered solid solution. This enables us to identify compounds that may be synthesizable or could be stabilized by entropy – thus allowing for more reliable materials discovery and design.

This work was supported by the U.S. D.O.E., Office of Science, BES, MSED (first principles calculations) and the LDRD Program of ORNL (simulations), managed by UT-Battelle, LLC, for the U. S. DOE using resources at NERSC and OLCF.