32 research outputs found
Measuring nonlinear stresses generated by defects in 3D colloidal crystals
The mechanical, structural and functional properties of crystals are
determined by their defects and the distribution of stresses surrounding these
defects has broad implications for the understanding of transport phenomena.
When the defect density rises to levels routinely found in real-world
materials, transport is governed by local stresses that are predominantly
nonlinear. Such stress fields however, cannot be measured using conventional
bulk and local measurement techniques. Here, we report direct and spatially
resolved experimental measurements of the nonlinear stresses surrounding
colloidal crystalline defect cores, and show that the stresses at vacancy cores
generate attractive interactions between them. We also directly visualize the
softening of crystalline regions surrounding dislocation cores, and find that
stress fluctuations in quiescent polycrystals are uniformly distributed rather
than localized at grain boundaries, as is the case in strained atomic
polycrystals. Nonlinear stress measurements have important implications for
strain hardening, yield, and fatigue.Comment: in Nature Materials (2016
Knowledgebase of Interatomic Models application programming interface as a standard for molecular simulations
Nanoscale modeling of materials often involves the use of molecular simulations or multiscale methods. These approaches frequently use empirical (fitted) interatomic potentials to represent the response of the material. As part of the open Knowledgebase of Interatomic Models (KIM) project (https://openkim.org), an application programming interface (API) for interatomic potentials has been developed in consultation with key members of the materials simulation community. The KIM API is beginning to emerge as a standard for atomistic simulations of materials. This API makes it possible for any KIM-compliant (KIM API conforming) simulation code (“Simulator”) to seamlessly use any KIM-compliant potential (“Model”) obtained from https://openkim.org. The KIM API is also necessary for the KIM Processing Pipeline in https://openkim.org to automatically compute the predictions of stored Models for a variety of material properties by linking them to computer programs called “Tests” that perform these calculations. The KIM API is lightweight and efficient, supports physical unit conversion, a variety of common neighbor list and boundary conditions used in atomistic simulations, and provides multilanguage support for C++, C, Fortran 2003, Fortran 90/95, and Fortran 77, allowing Simulators and Models written in any of these languages to work together