Seamless elastic boundaries for atomistic calculations

L Pastewka and TA Sharp and MO Robbins, PHYSICAL REVIEW B, 86, 075459 (2012).

DOI: 10.1103/PhysRevB.86.075459

Modeling interfacial phenomena often requires both a detailed atomistic description of surface interactions and accurate calculations of long- range deformations in the substrate. The latter can be efficiently obtained using an elastic Green's function if substrate deformations are small. We present a general formulation for rapidly computing the Green's function for a planar surface given the interatomic interactions, and then coupling the Green's function to explicit atoms. The approach is fast, avoids ghost forces, and is not limited to nearest-neighbor interactions. The full system comprising explicit interfacial atoms and an elastic substrate is described by a single Hamiltonian and interactions in the substrate are treated exactly up to harmonic order. This concurrent multiscale coupling provides simple, seamless elastic boundary conditions for atomistic simulations where near-surface deformations occur, such as nanoindentation, contact, friction, or fracture. Applications to surface relaxation and contact are used to test and illustrate the approach.

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