i-Rheo GT: Transforming from Time to Frequency Domain without Artifacts

M Tassieri and J Ramirez and NC Karayiannis and SK Sukumaran and Y Masubuchi, MACROMOLECULES, 51, 5055-5068 (2018).

DOI: 10.1021/acs.macromol.8b00447

We present a new analytical tool for educing the frequency dependent complex shear modulus of materials from computer-aided numerical simulations of their time-dependent shear relaxation modulus, without the need of preconceived models. The rheological tool is presented in the form of an open access executable named "i-Rheo GT", enabling its use to a broad scientific community. Its effectiveness is corroborated by analyzing the dynamics of ideal single mode Maxwell fluids and by means of a direct comparison with both bulk-rheology measurements and coarse grained molecular dynamics simulations data transformed via a generalized Maxwell model. When adopted to transform atomistic molecular dynamics simulations data, the unbiased nature of the tool reveals new insights into the materials' linear viscoelastic properties, especially at high frequencies, where conventional tools struggle to interpret the data and molecular dynamics simulations actually provide their most statistically accurate predictions. The wideband nature of i-Rheo GT offers the opportunity to better elucidate the link between materials' topologies and their linear viscoelastic properties-from atomic length scales at frequencies of the order of terahertz up to mesoscopic length scales of molecular diffusion phenomena occurring over time scales of hours.

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