Activated dynamics in thin films and stable glasses

• Applicant: Dr. Julian Helfferich
• Subject Area: Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics ; Theoretical Condensed Matter Physics
• Term: from 2015 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 278287554

Glassy films formed by vapor deposition display an extraordinary thermodynamic and kinetic stability which ordinary glasses, formed by cooling from the liquid state, would only attain after thousands of years of aging. The remarkable stability, evident in a very low enthalpy and high mechanical modulus, has been studied in experiments on vapor-deposited glasses for many organic molecules as well as metallic glasses. It is generally assumed that the stability observed in vapor-deposited glasses is due to an increased mobility of the particles at the free surface during the formation of the film. While a number of experimental studies of stable glasses have been conducted, only limited numerical and theoretical studies exist. Numerical studies are of very high interest as a complementary approach to experiments as they provide the tools to study the microscopic configurations and the microscopic dynamics in further detail. It is, in particular, of high interest to study how the macroscopic stability of vapor-deposited glasses is reflected in the microscopic dynamics of the constituent particles and whether the characteristic features of glass dynamics, activated dynamics, dynamic heterogeneities, and cooperative motion, persist to play a dominant role in stable glasses. This grant will enable me to join the group of Juan J. de Pablo at the Institute for Molecular Engineering at the University of Chicago to study the microscopic dynamics in simulations of stable glasses. In particular, I will quantify aging in the center and at the free surface, testing the hypothesis that the film ages faster at the surface, and specify the growth front observable in the devitrification of stable glasses. The research project will be conducted in close collaboration with the group of Mark Ediger at the University of Wisconsin, one of the leading experts in experiments on vapor-deposited glasses, and the group of Kenneth S. Schweizer, a distinguished expert for the theory of glass dynamics.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Dr. Juan de Pablo