High-throughput computation and materials databases have provided first principles predictions for hundreds of thousands of materials whose crystal structures are recorded in databases such as the Inorganic Crystal Structure Database (ICSD). However, many properties of real materials often depend on non-idealities in the structure that cannot be described in the crystallographic primitive cells. We will discuss examples of materials design via defects and disorder in oxides and nitrides. Solar thermochemical hydrogen generation is based on oxide redox chemistry, where a realistic technological process is viable only within a very narrow window for the enthalpies and entropies of reduction. From defect equilibria calculations, it is shown that the formation of charged O vacancies can provide an important source of entropy [1]. This approach is then applied to explain the exceptional performance of CeO2 and to guide further materials searches. Compared to oxides there are many fewer nitrides known. While the exceptional stability of the N2 molecule reduces the nitride formation enthalpy, nitrides can often form in a metastable state. Following a broad search for novel ternary nitrides [2], we predicted their structure and properties in the presence of disorder, which is prevalent growth with non-equilibrium deposition methods. The interplay between cation stoichiometry and oxygen incorporation, studied in Zn1+xSn1-xN2-2xO2x via supercell-defect and Monte-Carlo calculations can lead to surprising non-monotonic doping properties [3], and the formation of a novel phase at "magic compositions" that combine line-compound and solid-solution features. .

Computational design of oxides and nitrides in the presence of defects and disorder

2019 Fall National Meeting

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