Nuclear hyperfine interactions in critical metal AlB2-structured diborides and correlations to physical properties.

Nuclear magnetic resonance (NMR) measurements of the hyperfine parameters (quadrupolar, shifts) at the metal and boron sites are reported from an isomorphous set of eleven stable AlB2 structure-type space group 191 metal diborides, the main group metal diborides MgB2 and AlB2, and transition metal diborides ScB2, TiB2, VB2, CrB2, YB2, ZrB2, NbB2, HfB2, TaB2. Nuclear quadrupole resonance (NQR) studies were performed to locate resonances from 177Hf and 181Ta in the respective diborides. The electric field gradients, Vzz, nuclear quadrupole coupling constants, Cq, and Knight shift values, Kiso, at the both the metal and boron sites, are reported and are discussed in terms of current state-of-the-art quantum chemical first-principles calculations, as well as being correlated with electronic and cohesive properties of these materials. New experimental results and calculations are presented in addition to re-analysis of existing literature data to test hypotheses of how structure and composition can be tailored to achieve desired physical properties. This comprehensive set of experimental NMR data provides a direct link between measurable hyperfine parameters, calculated bonding parameters, and important physical properties including catalytic activity and asymptotic bulk hardness. The use of magnetic resonance for detection of critical metal diborides via their hyperfine interactions and linking these interactions to physical characteristics opens improved pathways for materials design with novel properties, as well as a method to fingerprint material signatures useful in the circular economy for resource identification, verification, recovery, and reuse.