Understanding colossal barocaloric effects in plastic crystals.

Area of Science:

• Materials Science
• Thermodynamics
• Solid-State Physics

Background:

• Neopentylglycol (NPG) is a plastic crystal known for colossal barocaloric effects (BCEs).
• BCEs offer a promising route for solid-state cooling applications using external pressure.
• Understanding the molecular mechanisms behind NPG's BCEs is crucial for developing advanced cooling materials.

Purpose of the Study:

• To investigate the role of intermolecular hydrogen bonds in the orientational order-disorder transitions of NPG.
• To elucidate the atomic-scale mechanisms governing the colossal barocaloric effects in NPG.
• To explore pressure-induced tuning of intermolecular interactions for optimizing BCEs.

Main Methods:

• Analysis of hydrogen bond strength and its influence on molecular ordering.
• Calculation of rotational entropy free energy and entropy changes.
• Investigation of pressure effects on hydrogen bond length and activation barriers.

Main Results:

• Intermolecular hydrogen bonds are key to NPG's orientational order.
• Thermal perturbation weakens the activation barrier for orientational disorder.
• External pressure reduces hydrogen bond length and enhances the activation barrier, tuning the order-disorder transition.

Conclusions:

• The study provides atomic-scale insights into NPG's order-disorder transitions and BCEs.
• Hydrogen bond dynamics are critical for understanding and optimizing barocaloric effects in plastic crystals.
• This research facilitates the molecular design of superior caloric materials for future cooling technologies.