First-principles design of strong solids: Approaches and applications

Abstract

In the design of strong solids, especially hard and superhard materials, this review article attempts to critically cover an extended field of first-principles derived mechanical properties by considering both intrinsic (i.e., crystal structures, bonding nature and strength) and extrinsic (i.e., nanostructures and interface characteristics) parameters. For the intrinsic parameters, firstly, the bonding topology and nature, elastic property and ductility-brittleness criterion provide critical physics on the understanding of the mechanical response of a crystal. Secondly, the ideal strength model, the generalized stacking fault energy model, and ab initio informed Peierls-Nabarro model uniquely quantify the fracture and plastic resistance of a crystal. Taking the extrinsic parameters into further consideration, the recent progress of first-principles investigations on the mechanical behavior of nanostructured solids and heterogeneous interfaces is selectively reviewed, targeted as the origin and/or carrier of the fracture or plastic deformation. These extrinsic parameters include the work of adhesion, the critical stresses for interfacial cleavage and glide and so on. Finally, by classifying the strong solids into intrinsically and extrinsically hard/superhard materials, two different rules are proposed: (1) three-dimensional short covalent bond networks with sufficiently high ideal strength and Peierls resistance and (2) nanosized crystallites/layers glued by strongly bonded thin interfaces.