ABSTRACT
A free energy perturbation method is used to systematically study the elastic properties of four common Gay–Berne nematogenic models; two with a length-to-diameter ratio κ = 3 [(3, 5, 1, 2) and (3, 5, 1, 3)], a model with κ = 4.4 parameterised for p-terphenyl (4.4, 20, 1, 1), and a discogen with κ = 0.345 (0.345, 0.2, 1, 2). In accordance with previous measurements, we find that for κ = 3, models, . We additionally find the latter two models in particular accurately capture the experimentally measured elastic ratios in apolar achiral systems. The (4.4, 20, 1, 1) model reproduces the elastic constant ratios of p-azoxyanisole remarkably well, and maps to within 30% of the absolute. The (0.345, 0.2, 1, 2) model elastic constants exhibit an unusual temperature dependence similar to recent experimental studies. Here we find
, in line with theoretical predictions. All models deviate from the mean-field expectation kii ∝ S2. These results represent a crucial first step towards quantitatively accurate coarse-grained liquid crystalline models of self-assembly and response, enabling one to choose a Gay–Berne model based on its measured elastic ratios rather than just its shape and energy anisotropy.
Graphical Abstract
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Acknowledgements
HS and JKW acknowledge computational resources at the Notre Dame Center for Research Computing (CRC). This work was supported by MICCoM, as part of the Computational Materials Sciences Program funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, under grant #0J-30521-0009A.
Disclosure statement
No potential conflict of interest was reported by the authors.