A New State Of Matter Turns A Solid World Into A Melting One

September 11, 1997

A new form of matter, clusters of atoms, has been oberved in recent years behaving in curious ways. Now research indicates that clusters have another, previously unsuspected property: they can melt at different temperatures from "solid" matter.

An experiment described in tomorrow's Science (Sept. 12) paints an exotic portrait of certain substances seemingly confounding nature by existing as a liquid, instead of a solid, at room temperature.

George Bertsch, a theoretical physicist at the University of Washington, describes how the experiment with clusters of sodium atoms found that the atoms did not follow sodium's normal pattern, melting at 97.8 degrees Centigrade (208 degrees Fahrenheit). Instead, the small clusters of atoms melted at minus 6 degrees Centigrade (21 degrees Fahrenheit), well below room temperature.

The discovery was the work of Hellmut Haberland at the University of Freiburg in Germany. Bertsch, who has been following the field of cluster research for the past decade, writes that as a result of the experiment, scientists are now challenged "to understand what happens to the liquid and solid phases in small particles."

European researchers are working on a number of practical applications for the cluster phenomenon. Attempts are being made to produce thin films of silicon clusters that would process signals carried by light. Others are researching the use of clusters to improve the magnetic recording of data. And Haberland has been reported to have produced clusters of the element molybdenum that will even stick to Teflon.

Clusters have been called a new type of matter, says Bertsch, because they appear to be a bridge between atoms and the world of normal size, and have strange magnetic, electrical and optical properties. What is particularly curious, he says, is that the properties of the clusters depend on the number of atoms they contain.

Bertsch notes that most clusters are very unstable collections -- "they touch a wall and they are gone." But a decade ago it was discovered that certain clusters contain "magic numbers" of atoms that make them particularly stable. These numbers begin with just two atoms, and continue through eight, 20 and 40 and into the hundreds of atoms.

The German researcher used magic-number clusters of 139 sodium atoms. The melting point was observed by forming condensation 'droplets', rather like hot steam hitting a cold window, and passing the condensate through a mass spectrometer and finally an electric field.

Bertsch concedes that the research is controversial, and there are physicists who insist there can only be one melting temperature for each of the 92 natural elements. But, he says, "as scientists we have to look at the evidence." What's more, he believes there is evidence that the same phenomenon that the German researcher demonstrated with sodium, also exists with atomic clusters of both tin and lead.

The UW scientist is hesitant to attempt an explanation of what is causing the lower melting point of these elements. However, he notes, it has been suggested that there is a relation to a theory known as surface melting: when a substance reaches melting temperature, only a small surface layer melts immediately. "As solid sodium reaches melting temperature, a small layer of liquid might form on top of the solid," he says. "In a cluster, all you would have is this outer, liquid layer."

It could be said, says Bertsch, that this new type of matter is "practically all surface." If there is already something strange happening at the surface of certain elements, "then you accentuate that behavior when you create clusters."
-end-
Contact Bertsch at (206) 543-2895, or at bertsch@phys.washington.edu

University of Washington

Related Sodium Articles from Brightsurf:

Sodium found to regulate the biological clock of mice
A new study from McGill University shows that increases in the concentrations of blood sodium can have an influence on the biological clock of mice, opening new research avenues for potentially treating the negative effects associated with long distance travel or shift work.

Researchers develop viable sodium battery
Washington State University and Pacific Northwest National Laboratory researchers have created a sodium-ion battery that holds as much energy and works as well as some commercial lithium-ion battery chemistries, making for a potentially viable battery technology out of abundant and cheap materials.

Elucidating the mechanism of a light-driven sodium pump
Researchers at the Paul Scherrer Institute PSI have succeeded for the first time in recording, in action, a light-driven sodium pump from bacterial cells.

Intravenous sodium nitrite ineffective for out-of-hospital cardiac arrest
Among patients who had an out-of-hospital cardiac arrest, intravenous sodium nitrite given by paramedics during resuscitation did not significantly improve their chances of being admitted to or discharged from the hospital alive, according to research presented at the American College of Cardiology's Annual Scientific Session Together with World Congress of Cardiology (ACC.20/WCC).

Study finds glutamates such as MSG can help reduce Americans' sodium intake
A new study indicates that the substitution of glutamates such as MSG for salt can reduce Americans' sodium intake by up to 7-8 percent.

High-performance sodium ion batteries using copper sulfide
Researchers presented a new strategy for extending sodium ion batteries' cyclability using copper sulfide as the electrode material.

Updated dietary reference intakes for sodium and potassium
A new report from the National Academies of Sciences, Engineering, and Medicine reviews current evidence and updates intake recommendations known as the Dietary Reference Intakes (DRIs) for sodium and potassium that were established in 2005.

Sodium intake associated with increased lightheadedness in context of DASH-sodium trial
Researchers at Beth Israel Deaconess Medical Center found that higher sodium intake, when studied in the context of the DASH-Sodium trial (Dietary Approaches to Stop Hypertension), increases lightheadedness.

Sodium is the new lithium: Researchers find a way to boost sodium-ion battery performance
NITech scientists have found the desirable component for sodium-ion batteries (SIB), which could contribute to boost SIB performance such as speed of charge.

Angiotensin receptor blockers normalize sodium excretion
Drugs that inhibit a hormone that constricts blood vessels also help improve sodium excretion in blacks who hold onto too much sodium in the face of stress, investigators report.

Read More: Sodium News and Sodium Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.