We propose in this paper a 1D model problem to study the convergence of surrogate approximations, using an atomistic-to-continuum coupling method, towards the solution of a full particle model. The 1D problem consists of a collection of springs that exhibits a local defect, materialized by a sudden change in the spring properties. The surrogate model is obtained by the Arlequin approach which introduces an overlap region in which the continuum and particle models are coupled together using Lagrange multipliers. The objective of the present work is to show, via numerical experiments, that the modeling error does indeed converge to zero as the distance of the overlap region from the defect and/or its size are increased.