Abstract. We study a force-based hybrid method that couples atomistic model with CauchyBorn elasticity model with sharp transition interface. We identify stability conditions that guarantee the convergence of the hybrid scheme to the solution of the atomistic model with second order accuracy, as the ratio between lattice parameter and the characteristic length scale of the deformation tends to zero. Convergence is established for hybrid schemes with planar sharp interface for system without defects, with general finite range atomistic potential and simple lattice structure. The key ingredient of the proof is regularity and stability analysis of elliptic systems of difference equations. We apply the results to atomistic-to-continuum scheme for a 2D triangular lattice with planar interface.Key words. Multiscale method, atomistic-to-continuum, stability analysis, force-based coupling AMS subject classifications. 65N12; 74S301. Introduction. Multiscale methods couple together atomistic and continuum models have received intense investigations in recent years; see, e.g., [1,11,23,30,31]. Generally speaking, there are two main categories of methods coupling atomistic and continuum models: energy-based methods and force-based methods. The energybased methods employ an energy that is a mixture of atomistic energy and continuum elastic energy. The energy functional is then minimized subject to suitable boundary conditions to obtain the deformed state of the system. The force-based methods work instead at the level of force balance equations. The forces derived from atomistic and continuum models are coupled together. The force balance equations supplemented with suitable boundary conditions are solved to obtain the deformed state of the system.From a numerical analysis point of view, the key issue for these multiscale methods is the consistency and stability analysis of the coupled schemes [11, Chapter 7]. In this paper, we study force-based atomistic-to-continuum hybrid methods in two and three dimension with sharp transition between the atomistic and continuum regions. In our previous work [22], we developed the stability analysis in general dimension for a force-based atomistic-to-continuum method with smooth transition between the two regions. The main focus of the current paper is to extend the stability analysis of [22] to hybrid schemes with sharp interface between atomistic and continuum models.Comprehensive reviews for force-based hybrid methods can be found in [25, Section 5 and Section 6] and [30, Section 12.5]. A class of force-based methods uses a handshake region (transition region) between the atomistic and continuum regions.