Christiane Alba-Simionesco, Cecile Dalle-Ferrier, Gilles Tarjus
We characterize the heterogeneous character of the dynamics of liquids approaching the glass transition through an experimental determination of the number of dynamically correlated molecules N_{corr} as obtained from dynamical susceptibilities. To do so, we have obtained a new set of dielectric spectroscopy data for liquid dibutyl-phtalate on a fine and extended temperature and pressure grid, and we have used it in conjunction with high-pressure data from the literature. We have been able to evaluate the contributions to N_{corr} that are due to fluctuations associated with density and with temperature separately, thereby improving the estimate of N_{corr}. We find that N_{corr} increases along the glass transition line, and more generally along any isochronic line, as pressure increases (up to 1 GPa), a result which is at odds with recent reports and theoretical predictions.
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http://arxiv.org/abs/1301.2451
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