Science and Software for Predictive Simulation of Chemo- mechanical Properties in Real Materials R. J. Bartlett, H-P. Cheng, & S.B. Trickey, U. Florida, DMR Forming and breaking chemical bonds under mechanical stress is vital in many industrial processes. Predictive simu- lations of such chemo-mechanical processes fundamentally require quantum mechanical descriptions. State-of-the-art QM calculations are limited in the number of atoms that can be handled. To beat this limitation, requires fast approximate QM and a multi-scale approach to embed the QM region in a much larger classical one. Nanorod fracture treated with a new pure fast QM scheme we developed is very different from all-classical fracture – and much more realistic! An all-QM silica nanorod fractures under uniaxial strain (movie)

Science and Software for Predictive Simulation of Chemo- mechanical Properties in Real Materials R. J. Bartlett, H-P. Cheng, & S.B. Trickey, U. Florida, DMR Here is a movie of water dissociation on the amorphous silica surface from the hybrid quantum-classical model; only the QM region is shown Water weakens silica dramatically. Why? How? Quantum-mechanics is essential for realism, classical mechanics for speed. Here’s a hybrid silica surface model. The QM region contains 31,74, & 209 Si,O atoms in the three boxes, repectively

Science and Software for Predictive Simulation of Chemo- mechanical Properties in Real Materials R. J. Bartlett, H-P. Cheng, & S.B. Trickey, U. Florida, DMR How does water interact with the nanorod? Understanding this would give us a leg up on how to embed the QM regime in a proper classical regime. In this movie, we look down on silica rings from the middle of the nanorod and watch a water dimer help break a silicon-oxygen bond. Notice the similarity with the amorphous surface in the hybrid simulation..