Solid-state refrigeration technology based on caloric effects is
promising to replace the currently used vapor compression
cycles, due to its numerous potentials for reducing electricity
consumption and worldwide emission of greenhouse gases. Recent
high-pressure experiments have reported that plastic crystal
neopentylglycol (NPG) exhibits colossal barocaloric effects
(CBCEs) with record-high entropy changes near room temperature,
offering exciting prospects for the field of solid-state cooling
through the application of moderate pressures. However,
the complete microscopic mechanism remains unestablished
so as to further push forward the development and application.
Here, we conduct a comprehensive study combing density
functional theory calculations (DFT) and molecular dynamical
simulations (MD), along with Raman spectroscopy and neutron
inelastic scattering measurements on NPG plastic crystals.
We reveal that the formation of intermolecular hydrogen bond
ladder plays a key role in the orientational order of NPG molecules
in monoclinic phase, and the activation barrier of orientational
disorder is prominently suppressed owing to the hydrogen
bond broken in cubic phase, contributing significantly to
the entropy changes which substantially lowers the total Gibbs
free energy in the monoclinic-to-cubic phase transition.
