CBET 1404991/1404823/1404919 Murthy (U Texas at Austin), Mahadevan (Vanderbilt), Strachan (Purdue)
During the last few years, the ability to experimentally probe physical phenomena at the nanoscale has improved dramatically. Experimental techniques are producing detailed nanoscale data on heat transport in materials such as graphene and silicon, but there are significant questions about whether these data are being interpreted correctly. One issue is that the theory used to interpret these data is too simplistic for the highly non-equilibrium regimes involved. Another issue is that there is significant variability in nanoscale measurements because of the extremely small length and time scales involved. In order to use experimental data to improve theory, one must fully account for measurement uncertainty, statistical variability in nanoscale fabrication techniques, and variability in material properties, and develop a systematic way to identify knowledge gaps in current models using these uncertain data. In this project, we propose to merge two hitherto distinct fields, decision science and phonon transport simulation, to create the first-ever decision framework for the systematic development and improvement of nanoscale thermal transport theory. The work will impact a wide variety of consumer applications including microelectronics, energy conversion and energy storage.
The research and simulation tools developed in the project will be disseminated to the research community and to the graduate and undergraduate programs at UT Austin, Purdue and Vanderbilt through Purdue's nanoHUB, along with educational modules and tutorials to help broaden use. All three schools will actively engage their existing and highly-effective programs to recruit women and underrepresented minorities into their research programs. UT Austin will draw undergraduate research projects from this work to integrate into their innovative 35-in-5 Women in ME initiative which aims to increase the percentage of women in their freshman Mechanical Engineering batch to 35% by 2018.
The overall objective of this proposal is to develop a deeper understanding of highly non-equilibrium phonon transport in nanomaterials. During the last few years, as our ability to probe nanoscale thermal and electronic transport has improved, it has come to be recognized that non-equilibrium transport dominates the performance of many emerging nanotechnologies and measurement systems. Experimental techniques such as micro-Raman and micro Brillouin Light Scattering are producing detailed wave-vector resolved phonon transport data which must be interpreted correctly if their true potential is to be unleashed. Though theory and computational predictions are also being developed simultaneously, few direct comparisons of measurements and theory have been made at this granularity and there is little confidence that existing theories are adequate. The project will combine detailed models and experiments for optically-excited phonon transport in graphene, bulk and thin film silicon and other materials with a Bayesian decision framework to develop better theories, interpret emerging experiments correctly, design better experiments and simulations and to quantify the uncertainty in our predictions. A unique feature of the project is the use of classical molecular dynamics (MD) simulations to evaluate model form uncertainty in phonon transport simulations based on the semi-classical phonon Boltzmann transport equation (BTE). Furthermore, by exploiting unique micro-Raman and micro Brillouin Light Scattering measurements being performed UT Austin in a parallel NSF project, we will have a one-of-a-kind opportunity to obtain spatially and mode-resolved phonon transport data that can significantly improve the quality of our models.
The research plan includes the use of a Bayesian framework to (i) quantify model form uncertainties due small-perturbation assumptions in the modeling of phonon scattering through calibration with molecular dynamics (ii) calibrate interatomic potentials to spatially and spectrally-
