The objective of this research is to develop device modeling tools for NEMS, to extract compact models and to develop multi-phenomena based circuit simulation tools that can model NEMS along with other components of integrated nanosystems. The device modeling research will focus on self-consistent analysis of three mixed-energy domains - namely, electrostatics, mechanical and van der Waals energy domains. Hierarchical physical theories for electrostatics will be combined with van der Waals interactions and nanometer scale mechanical theories. The final goal of the device modeling effort is to extract parameterized reduced-order or compact models that can be used as input models for circuit simulation of integrated nano electromechanical systems. The circuit modeling research will focus on the enhancement of the SPICE-based simulation framework with the capability to support multi-physics and multi-phenomena for CAD-based conceptualization, design exploration and synthesis of nanosystems. Specifically, the circuit modeling effort will focus on the circuit representation of the non-electrical components of NEMS as well as on the development of efficient time- and frequency-dependent simulation of NEMS.