Here we study how changes in temperature and pressure affect the dynamic heterogeneity in glass formers by using dielectric, volumetric, and heat capacity experimental data for two typical supercooled van der Waals liquids, 1,1′-bis ($p$-methoxyphenyl) cyclohexane (BMPC) and $o$-terphenyl (OTP). We demonstrate that these thermodynamic variables are not equivalent. We find that changes in temperature exert a stronger influence on heterogeneous dynamics than those in pressure, and the degree of heterogeneity in different thermodynamic conditions is mirrored in some way in corresponding structural relaxation times.

• Received 25 January 2012

DOI:https://doi.org/10.1103/PhysRevB.85.220201