Electronic and structural properties of TiB2: Bulk, surface, and nanoscale effects

Titanium diboride (TiB2), is a widely used hard material that comprises graphene-like layers of B and intercalated Ti atoms. Here we report the results of extensive first-principles calculations on key properties of bulk TiB2, TiB2 surfaces, and TiB2 nanocrystals (NCs). The computational approach is first validated based on the agreement between calculated structural and electronic properties of bulk TiB2 and available experimental and theoretical data. We then obtain the formation energies for several surface cuts and use these values to construct TiB2 NCs based on the Wulff theorem. Finally, we demonstrate by studying the adsorption of small molecules that hydrogen and oxygen adatoms can be attached through strongly exothermic chemisorption reactions on TiB2 surfaces. Likewise, water molecules bind on various TiB2 surfaces and NC facets, with an energetic preference for the latter. The results are relevant to applications that depend on reactivity-related TiB2 properties, for example resistance to corrosion and interactions with water-based solutions.