Mechanics analysis and atomistic simulations of nanobridge tests

The present work carries out mechanics analysis and atomistic simulations of nanobridge tests under large deformation. The nanobridge test is a three-point bending test on a nanowire sample with two clamped ends. The bending behavior of a tested nanowire under large deformation is mechanically analyzed, by treating a nanowire as a composite of a three-dimensional core, two-dimensional surfaces, and one-dimensional edges, and approximated by two loading steps corresponding to pure bending and tension, respectively. The two step loadings can be easily implemented in atomistic simulations and yield the strain energy of the tested nanowire in a closed form so that the analysis of simulation results becomes straightforward. Atomistic simulations of nanobridge tests on Si and SiC nanowires were conducted to demonstrate the developed approach. The surface stiffness and edge stiffness determined from the simulations of nanobridge tests are consistent with those determined from the tensile-compressive and pure bending simulations, thereby indicating that the surface stiffness and edge stiffness are material properties, independent of the loading condition, although the size-dependent Young's modulus is more significant in the nanobridge test than that in the tensile-compressive test.