An electronic criterion for assessing intrinsic brittleness of metallic glasses

Bulk metallic glasses (BMGs) are characterized by a number of remarkable physical and mechanical properties. Unfortunately, these same materials are often intrinsically brittle, which limits their utility. Consequently, considerable effort has been expended searching for correlations between the phenomenologically complex mechanical properties of metallic glasses and more basic properties, such correlations might provide insight into the structure and bonding controlling the deformation properties of BMGs. While conducting such a search, we uncovered a weak correlation between a BMG's work function and its susceptibility to brittle behavior. We argue that the basis for this correlation is a consequence of a component of the work function - the surface dipole - and a fundamental bond property related to the shape of the charge density at a bond critical point. Together these observations suggest that simple first principle calculations might be useful in the search for tougher BMGs.