Nonlocal Elastic Constants of Centrosymmetric Homogeneous Lattice Structure and Inhomogenous One

Abstract

Nonlocal elastic constants have been related to atomistic properties through a macro-micro linking approach proposed in a previous paper(Trans.of JSME, Vol.62, No.601, A(1996), p.2054-2059). Using the derived relations, these material constatns can be estimated only by atomistic quantities of force constants and neighboring lattice configuration. In the present study, centrosymmetric homogeneous bulk is first taken up. Agreement between the number of independent components of these elastic constants and the results from analytical estimation by invariance of transformation on an isotropic tensor is demonstrated. Then, the less symmetric surface and the high Σ-value grain boundary are computationally constructed by molecular dynamics simulations in order to examine inhomogeneous nonlocal effects. It is found that atomistic inhomogeneity increases nonlocal material properties, while the characteristic length derived from the ratio of the 6th-order to the 4th-order elastic constants is smaller than a lattice parameter.