Direct Measurement of Competing Quantum Effects on the Kinetic Energy of Heavy Water upon Melting

Abstract

Even at room temperature, quantum mechanics plays a major role in determining the quantitative behaviour of light nuclei, changing significantly the values of physical properties such as the heat capacity. However, other observables appear to be only weakly affected by nuclear quantum effects (NQEs): for instance, the melting temperatures of light and heavy water differ by less than 4 K. Recent theoretical work has attributed this to a competition between intra and inter molecular NQEs, which can be separated by computing the anisotropy of the quantum kinetic energy tensor. The principal values of this tensor change in opposite directions when ice melts, leading to a very small net quantum mechanical effect on the melting point. This paper presents the first direct experimental observation of this phenomenon, achieved by measuring the deuterium momentum distributions n(p) in heavy water and ice using Deep Inelastic Neutron Scattering (DINS), and resolving their anisotropy. Results from the experiments, supplemented by a theoretical analysis, show that the anisotropy of the quantum kinetic energy tensor can also be captured for heavier atoms such as oxygen.

References in corpus (7)

• Competing quantum effects in the dynamics of a flexible water model
• Nuclear quantum effects in water
• Nuclear quantum effects in solids using a colored-noise thermostat
• Efficient first-principles calculation of the quantum kinetic energy and momentum distribution of nuclei
• Accelerating the convergence of path integral dynamics with a generalized Langevin equation
• Unraveling quantum mechanical effects in water using isotopic fractionation
• Nuclear quantum effects in ab initio dynamics: theory and experiments for lithium imide

Cited by in corpus (11)

• How van der Waals interactions determine the unique properties of water
• Nuclear quantum effects enter the mainstream
• Effect of quantum nuclear motion on hydrogen bonding
• Quantum fluctuations and isotope effects in ab initio descriptions of water
• Inverse Temperature Dependence of Nuclear Quantum Effects in DNA Base Pairs
• Nuclear Quantum Effects in liquid water at near classical computational cost using the adaptive Quantum Thermal Bath
• Thermal neutron cross sections of amino acids from average contributions of functional groups
• Quantum kinetic energy and isotope fractionation in aqueous ionic solutions
• Isotopic fractionation in proteins as a measure of hydrogen bond length
• Using a monomer potential energy surface to perform approximate path integral molecular dynamics simulation of ab-initio water with near-zero added cost
• Anisotropy of the proton kinetic energy as a tool for capturing structural transition in nanoconfined H${}_2$O