Measuring Elastic Constants of Liquid Crystals In-Silico using Enhanced Free Energy Sampling

C.L. Phillips, A. Joshi, J. Whitmer, J. de Pablo
Argonne National Laboratory,
United States

Keywords: liquid crystals, informatics, modeling

Summary:

The elastic properties of liquid crystals play a crucial role in applications, determining the macroscopically observable response of the material to a change in its environment. In particular, when liquid crystals are used in molecular sensing applications, good performance is linked to a dramatic reorganization of the material when exposed to miniscule quantities of analyte. Designing materials for these applications requires that the material coefficients determining surface--elastic energy balances be known with exquisite precision. However, elastic coefficients such as bend, twist, splay, and saddle-splay, are difficult quantities to extract from experiment, often requiring indirect measurements through instability analyses. By combining high performance computing resources with advanced simulation tools and methods, we may instead use molecular simulations to extract these properties. Specifically, we utilize a method isolating single modes of deformation in conjunction with advanced free-energy sampling methods to extract elastic constants of real materials in silico. This type of computational methodology promises the ability to rationally design new materials with desired properties, shortening the cycle of material discovery.