Condensed Matter Physics, 2020, vol. 23, No. 2, 23801
DOI:10.5488/CMP.23.23801
arXiv:2001.11424
Title:
On the stress overshoot in cluster crystals under shear
Author(s):
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G.P. Shrivastav
(Institut für Theoretische Physik and Center for Computational Materials Science (CMS), TU Wien,
Wiedner Hauptstraße 8-10, A-1040 Wien, Austria),
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G. Kahl
(Institut für Theoretische Physik and Center for Computational Materials Science (CMS), TU Wien, Wiedner Hauptstraße 8-10, A-1040
Wien, Austria)
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Using non-equilibrium molecular dynamics simulations we study the yielding behaviour of a model cluster crystal formed by ultrasoft particles
under shear. We investigate the evolution of stress as a function of strain for different shear rates,  , and temperatures.
The stress-strain relation displays a pronounced maximum at the yielding point; the height of this maximum, σp, increases
via a power law with an increasing shear range and tends to saturate to a finite value if the limit shear rate goes to zero
(at least within the considered temperature range). Interestingly, this behaviour can be captured by the Herschel-Bulkley type model which,
for a given temperature, allows us to predict a static yield stress σp0 (in the shear rate tending to zero limit),
a characteristic timescale τc, and the exponent α of the above-mentioned power-law decay of the
σp at high shear rates. Furthermore, for different temperatures, the σp can be scaled as
functions of onto a single master curve when scaled by corresponding τc and
σp0. Moreover, for a given shear rate, σp displays a logarithmic dependence on
temperature.
Again, the σp–T curves for different shear rates can be scaled on a single logarithmic master curve when scaled by
a corresponding fitting parameters.
Key words:
rheology, cluster crystals, yielding, molecular dynamics, stress overshoot
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