"The main goal of this proposal is to systematically develop atomic scale models of concentrated multi-component alloys. To this end, we will derive empirical interatomic potentials for W and Ti-based alloys and carry out simulations of thermodynamic, kinetic and mechanical properties. In this fashion, we aim to provide a pathway to an improved atomic scale understanding of these materials. The unique features of the present proposal are a novel approach to modeling the chemistry of multi-component systems and new algorithms for simulating alloy microstructures taking into account structural, chemical and temperature effects.Most alloys contain at least three key components. Yet at present almost all interatomic potentials are constrained to the description of binary interactions. We will adopt a recently developed scheme devised to overcome these limitations and generate interatomic potential models for concentrated multi-component alloys. Based on these models we will carry out an extensive characterization of phase diagrams, short and long-range order, precipitation, meta-stable phases, and mechanical properties. To this end, we will apply a novel hybrid molecular-dynamics/Monte Carlo algorithm that is capable of simultaneously taking into account structural, chemical and temperature effects. The method will be extended to allow for a variable total number of particles to enable studies of general solid-solid interfaces."