Coupling of length scales in MEMS modeling: the atomic limit of finite elements

We discuss concurrent multiscale simulations of the dynamic and temperature-dependent behavior of sub-micron MEMS, especially micro-resonators. The coupling of length scales methodology we have developed employs an atomistic description of small but key regions of the device, consisting of millions of atoms, coupled concurrently to a finite element model of the periphery. This novel technique accurately models the behavior of the mechanical components of MEMS down to the atomic scales. This paper addresses general issues involved in this kind of multiscale simulation, with a particular emphasis on how finite elements can be extended to ensure a reliable model as the mesh spacing is refined to the atomic scale. We discuss how the coupling of length scales technique has been sued to identify atomistic effects in sub-micron resonators.