Microscopic view of materials properties of liquids: An atomic scale perspective

Abstract

Microscopic understanding of liquid properties is essential for advancing a wide range of applications from energy applications such as nuclear reactors and batteries to biomedical applications including drug delivery and microfluidics. However, intrinsic dynamic disorder and lack of structural periodicity in liquids have presented fundamental challenges in developing rigorous microscopic theories of their thermodynamic and dynamic behavior. Recent breakthroughs in computational power and experimental metrologies have driven significant progress in unraveling the complex atomic scale dynamics of liquids. In this Review, we provide a brief historical context of liquid state physics and explore recent advances through theoretical, computational, and experimental approaches. For theoretical and computational approaches, instantaneous normal mode and velocity autocorrelation function calculations are discussed. For experiments, we focus on X-ray and neutron scattering techniques that probe liquid dynamics at the atomic level. Finally, we highlight emerging opportunities and future directions in the study of liquid atomic dynamics.

Figures (17)

• Figure 1: Visualization of gas pressure via a kinetic model of atoms and molecules by Bernoulli in 1738 bernoulli_hydrodynamica_1738.
• Figure 2: A representative phase diagram (temperature vs. pressure) of matter. Slopes of the boundaries depend on the materials.
• Figure 3: A schematic demonstrating spectrum of matter from solid to gas and how liquids are often viewed: either a condensed matter or a fluid.
• Figure 4: Temperature dependent thermal conductivity for various crystals from diamond to lead telluride. Circles are measurements and curves are first principles calculations based on normal modes. Figure is from Ref. mcgaughey_phonon_2019.
• Figure 5: Instantaneous normal mode density of states for Lennard-Jones liquids at two temperatures. Solid curve corresponds to temperature 2.5 times higher than that of dashed curve. Figure is from Ref. keyes_instantaneous_1997 and $x$-axis is in normalized frequency units. Modes with imaginary frequencies are plotted in the negative $x$-axis. As temperature increases, more modes become imaginary.