Isochronal superposition and density scaling of the α-relaxation from pico- to millisecond

Henriette Wase Hansen, Bernhard Frick, Simone Capaccioli, Alejandro Sanz, Kristine Niss

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The relaxation dynamics in two van der Waals bonded liquids and one hydrogen-bonding molecular
liquid are studied as a function of pressure and temperature by incoherent neutron scattering
using simultaneous dielectric spectroscopy. The dynamics are studied in a range of alpha relaxation
times from pico- to milliseconds, primarily in the equilibrium liquid state. In this range, we find that
isochronal superposition and density scaling work not only for the two van derWaals liquids but also for
the hydrogen-bonding liquid, though the density scaling exponent is much smaller for the latter. Density
scaling and isochronal superposition are seen to break down for intra-molecular dynamics when
it is separated in time from the alpha relaxation, in close agreement with previous observations from
molecular dynamics simulations.
TidsskriftJournal of Chemical Physics
Udgave nummer21
StatusUdgivet - 2018

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