This is an award under the KDI initiative that is managed by DMR and CTS. The PIs seek to describe structural and dynamical order during a phase transformation. This order can range over the continuum between perfect order of a crystalline material and the nearly total absence of long-range order of the amorphous phase. The large dimensionality needed to represent the total dynamical order of a system will be reduced to a small set of parameters to define the possibility of a transformation between phases. Unified models will be provided which define a set of order parameters that can be applied to materials with various levels of order; an accuracy of distinction between phases of more than 90% will be attempted. Test bed materials are both organic (small rigid thiophenes that are ideal for comparison to simulation studies) and inorganic (various morphological forms of silicon). To model these accurately and to make large-scale dynamical simulations needed to study order transformations, a new quantum mechanical algorithm will need to be developed to allow calculations with at least the speed and accuracy of current tight-binding methods. The PIs propose to develop such a quantum mechanical algorithm based on the Harris functional and plan to incorporate Voter's hyperdynamic techniques to increase accessible simulation times. Reverse Monte Carlo techniques will also be used to develop a scheme for creating systems with a chosen extent of order. Using this suite of linked simulation tools that can describe processes from nanoscopic to macroscopic length scales, the PIs will establish co-relation and phase transformation probability of these material models subject to processing conditions (thermal cycles, nucleation sites, plasma-enhanced precursors, etc.) The proposed simulation methodology will be tested on a solidifying interface structure, examining and understanding the roles of molecular architecture and inter-atomic potentials. Quantitative links will be developed that connect processing conditions and the resulting structure in complex materials. The critical point at which the final structure of the solid is predictable or controllable given a metastable starting point of known order. %%% This is an award under the KDI initiative that is managed by DMR and CTS. The proposed work constitutes a new computational challenge. Observing that the ability to tailor local and long-range structural order in materials is of great technological utility, the PIs seek to develop large-scale numerical simulation techniques that would be used to provide a fundamental description of structural order and processing in these materials. Work will be performed in conjunction with experiments on model systems of commercial interest. This work will contribute to the field of organic optoelectronics, creating polymers with controlled properties, in modeling the low-temperature processing of silicon, the integration of biosensors, and stacked 3D components. It will lead to a coupling of organic and inorganic systems for biosensors. ***
