A Physical Model of Nanotwin Unit and Orientation Organization for Designing Mechanical Performance: Cases of InSb, GaAs, ZnS

Abstract

Functional unit and organization (FUO) paradigm starts with functional units and assembles these functional units into specific organizations to optimize material performance. An advantage of FUO paradigm is interpretation of physical essence of traditional structure–performance relationships. Experimental achievements based on FUO paradigm abound in recent years, demanding theoretical explanations for further quantitative material design. Following FUO paradigm, here a three‐step model (bond‐region‐structure) of nanotwin (NT) unit and orientation organization to optimize mechanical performance is established. First, anisotropic elasticities of representative bonds and assembled regional elastic constants are evaluated. Second, yield conditions of different regions, which are summarized as critical resolved shear stress (CRSS) criteria of NT structure, are quantified. Third, anisotropic yield strengths of NT structure from the regional elastic constants and CRSS criteria are derived. This FUO‐based model is implemented into InSb, GaAs, and ZnS, predicted elastic constants and yield strengths are validated with molecular dynamics (MD) simulations. The method is more efficient than MD with comparable accuracy, and is also flexible to combine with density function theory and experiment. This demonstration sets foundation of NT unit and orientation organization design for achieving optimum mechanical performance.

Deformation and Failure Mechanisms of Element-Substituted Thermoelectric Type-I and Type-VIII Clathrates

“…Generally, the elastic properties are affected by the interatomic force, chemical bond length, bond angle, and crystal structure Table lists the clathrate elastic constants calculated by the DFT method, as well as the bulk modulus ( B ), shear modulus ( G ), [100] direction Young’s modulus ( E ), Poisson’s ratio ( v ), and Vickers hardness ( Hv ) predicted by the Voigt–Reuss–Hill approximation and Chen’s method .…”

“…Generally, the elastic properties are affected by the interatomic force, chemical bond length, bond angle, and crystal structure. 39 The shear stress−strain responses of four type-I clathrates along the (110)/[001] slip system and three type-VIII clathrates along the (100)/[010] slip system are calculated, as shown in Figure 3. It can be found that within a similar crystal structure, the ideal strength and elastic constants C 44 , shear modulus G are positively correlated.…”