Surprise electron behavior may lead to new states of matter

What happens when the metal osmium (Os) is subjected to pressure twice that found at the center of Earth? An international team of researchers has discovered a never before seen atomic phenomenon that provides surprising insights into how matter works – and may even lead to the discovery of new states of matter.

Previously, the greatest amount of pressure that could be applied, sustained, and measured using human-made technology approximated that found at Earth’s core, about 350 gigapascals (3,500,000 atmospheres). However, researchers found a way to expose osmium crystal to pressure more than double that previously created in a lab, achieving 7.7 million times the pressure at Earth’s surface. Osmium has one of the highest densities of all elements, along with one of the highest melting points at 3,045 °C (5,513 °F), and is almost as incompressible as diamond.

Osmium crystals. Credit: Alchemist-hp (Wikimedia Commons)

For the experiment, researchers developed synthetic diamonds and added them to a diamond anvil cell, a compression method used by scientists since the 1950s. In this way, the pressure to which they subjected the osmium crystal was drastically increased to more than 770 gigapascals (7,700,000 atmospheres). Such pressure could conceivably exist at the center of other, larger planets.

Cross-section of a traditional diamond anvil cell. Credit: Tobias, 1984 (Wikimedia Commons)

High pressure is known to change material properties. This is because compression forces atoms closer together, causing electrons to interact with each other. It is the outer, or valence, electrons that determine the properties of elements. Whereas valence electrons are mobile and interact with neighboring atoms, the electrons nearest the atom’s nucleus remain stable. (Read more about how electron configuration affects chemical properties in our module The Periodic Table of Elements.)

Atomic structure of fluorine (F). Electrons in the outer orbital interact with neighboring atoms. Credit: Julian Habekost and Jonas Konrad (Wikimedia Commons)

However, findings of this latest research challenge long-held beliefs about the behavior of electrons. Scientists in Sweden, Germany, the US, the Netherlands, France, and Russia collaborated on the project, which culminated in results that defied expectations on two counts: First, osmium’s valence electrons were not significantly affected in spite of the pressure. Second, the electrons closest to the nucleus of the atom began to interact with each other, showing that in extreme conditions, the stable electrons at the core of an atom behave differently.

This new understanding of matter may lead to the development of materials capable of withstanding extreme conditions. Further, “the phenomenon means that we can start searching for brand new states of matter,” Igor Abrikosov, leader of the project’s theoretical team, stated in an August 24 news release from Linköping University in Sweden. Results of the study appeared in an online publication of Nature (August 24, 2015).

The surprise findings “made us rethink things, and go back to the theories,” said Abrikosov. Without question, the key to advancing scientific knowledge is found in the interplay between theory and experimental observation. In this way, explanations of the natural world are refined and revised in light of new data. This is the nature of scientific knowledge – and the very heart of science.

LEARN MORE

For an overview of solids, liquids, gases, plasmas, Bose-Einstein condensates, and other less common states of matter, see our module States of Matter.

In other news on states of matter, advances in trapping plasma and holding it in a steady state may eventually result in a way to generate affordable energy. (See Daniel Clery’s Dark horse scores a fusion coup, Science, August 28, 2015.)

See our blog post about a recently discovered state of matter called the dropleton.

Read about a development that sheds new light on strange matter on phys.org.

Written by Bonnie Denmark

Bonnie Denmark holds an MA in linguistics and teacher certification in English, ESL, and Spanish. She has devoted her professional life to educational and accessibility issues as a computational linguist, multimedia curriculum developer, educator, and writer. She has also worked nationally and internationally as a language instructor, educational technology consultant, and teacher trainer. Bonnie joined the Visionlearning team as a literacy specialist in 2011, assisting the project by developing comprehension aids for science modules and creating other STEM learning materials.