Collaborative Research: Directed Design of Self-Assembling Materials: Enabling therModynamic Steering on Parallel computing clusters

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Self-assembly and directed assembly are widely utilized and powerful routes to the creation of advanced functional, nanostructured, or hierarchically structured materials. To date, progress in the design of advanced materials via self-assembly or directed assembly has been largely empirical, with limited theoretical understanding or control of the self-assembly process. At the most fundamental level, one would like to understand how a given state of mesoscale or macroscale self-assembly is encoded in the chemical structure of its molecular constituents, and to exploit this understanding to design tailor-made materials with specific desired properties. This research involves the development of thermodynamic steering, a set of novel computational methods for the first-principles design of advanced materials by active steering of a statistical mechanical system through chemical structure space toward a target state having prescribed collective properties. Thermodynamic steering involves mapping the free-energy landscape of self-assembling materials as a function of chemical structure over a range of thermodynamic conditions to identify microscopic constituents that self-assemble into a specified target structure. This is challenging because the 'search space' (the space of all possible chemical variations of microscopic constituents) and the 'target space' (the space of all competing states of mesoscale or macroscale self-assembly) are very high-dimensional spaces, precluding systematic exploration. These challenges are addressed through implementation of importance sampling methods for preferentially exploring the most relevant regions of search space, development of algorithms for rapidly generating libraries of competing thermodynamic states, application of modern methods for free energy computation in molecular simulations, and efficient use of parallel computing clusters. This methodology is applied to the design of spherical colloids that spontaneously assemble into unusual crystal structures (e.g., the diamond lattice).