An advanced nuclear technique has been used to find the first experimental evidence to confirm a universal law that provides insights into the complex energy states for liquids.
The work was published in the Journal of Physical Chemistry Letters and featured on the front cover.
The answer to a question that has been elusive for at least a century was provided in a paper published in PNAS in 2021.
The distribution of complex energy states for liquids has been solved by the elegant mathematical theory.
One of the most important quantities in the physics of matter is the distribution of the waves that travel in the material. The University of Milan website states that it is important as it is the starting point for calculating and understanding some fundamental properties of matter.
The big problem with liquids is that there are other types of excitations related to low energies of the disordered motion of atoms and molecules that are almost absent in solids. These excitations are linked to the chaotic chaos of the molecule but are still very important, especially at low energies. The INMs that correspond to energy states described by imaginary numbers are very difficult to deal with in mathematics.
The Center for Neutron Scattering at ANSTO has used the time-of-flight neutron spectrometer Pelican to measure the densities of states for several liquid systems. The Pelican instrument has a very high sensitivity to measure the movements of the waves.
The figure below shows the linear relationship of the density of states with low frequencies as predicted by Matteo Bagglioli.
The small team that included a University of Wollongong PhD candidate decided to focus on re-analyzing past experimental data from a new perspective to prove the new law.
Dr. Yu is the corresponding author of the paper, and he said that the exercise not only achieved a great outcome, but also gave a good introduction to neutron spectroscopy to the student.
The work will help them address questions relating to phase transitions in superionic liquids.
Major challenges arise because liquids are not mechanically stable, as the atoms in a liquid diffuse and the liquid as a whole will flow.
The universal law is based on a theoretical framework, known as instantaneous normal modes, which prescribes a set of instantaneous forces, frequencies, and velocities as quantities.
The existence of a small fraction ofimaginary modes made it difficult to derive a theory to predict the density of states in liquids.
maginary modes represent the fact that a liquid is not stable. The atoms in a liquid are interacting with one another but not in the same way as a solid. The atoms are not going to be restored to the same configuration after an interaction. The atoms will slide past each other.
The potential energy surface of a liquid is reflected by the imaginary modes. If you think of a surfer on an ocean wave, it is a very complex energy landscape. The atoms in the liquid follow the wave's curves. The atoms can be in a position on the crest, under the surfboard or in the trough.
The law will play a similar role to the Debye law in liquids. It will serve as the foundation for the whole research field.
More information: Caleb Stamper et al, Experimental Confirmation of the Universal Law for the Vibrational Density of States of Liquids, The Journal of Physical Chemistry Letters (2022). DOI: 10.1021/acs.jpclett.2c00297The Universal law for the density of states of liquids was presented in the National Academy of Sciences. 10.1073/pnas.
Citation: Surfing at the atomic scale: Scientists experimentally confirm new fundamental law for liquids (2022, April 14) retrieved 14 April 2022 from https://phys.org/news/2022-04-surfing-atomic-scale-scientists-experimentally.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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