Sodium loses its luster: A liquid metal that's not really metallic

September 26, 2007
Sodium loses its luster: A liquid metal that's not really metallic
Unlike other solid metals, sodium melts differently when additional pressure is added. Image: Kwei-Yu Chu/LLNL

When melting sodium at high pressures, the material goes through a transition in which its electrical conductivity drops threefold. In a series of new calculations, Lawrence Livermore National Laboratory scientists describe the unusual melting behavior of dense sodium.

“We found that molten sodium undergoes a series of pressure-induced structural and electronic transitions similar to those observed in solid sodium but beginning at a much lower pressure,” said LLNL’s Eric Schwegler.

Schwegler and former colleagues Stanimir Bonev, now at Dalhousie University in Nova Scotia, and Jeans-Yves Raty at FNRS-University of Liège in Belgium report the new findings in the Sept. 27 edition of the journal, Nature.

Earlier experimental measurements of sodium’s melting curve have shown an unprecedented pressure-induced drop in melting temperature from 1,000 K at 30 GPa (30,000 atmospheres of pressure) down to room temperature at 120 GPa (120 million atmospheres of pressure).

Usually when a solid melts, its volume increases. In addition, when pressure is increased, it becomes increasingly difficult to melt a material.

However, sodium tells a different story.

As pressure is increased, liquid sodium initially evolves into a more compact local structure. In addition, a transition takes place at about 65 GPa that is associated with a threefold drop in electrical conductivity.

The researchers carried out a series of first-principle molecular dynamic simulations between 5 and 120 GPa and up to 1,500 K to investigate the structural and electronic changes in compressed sodium that are responsible for the shape of its unusual melting curve.

The team discovered that in addition to a rearrangement of the sodium atoms in the liquid under pressure, the electrons were transformed as well. The electronic cloud gets modified; the electrons sometimes get trapped in interstitial voids of the liquid and the bonds between atoms adopt specific directions.

“This behavior is totally new in a liquid as we usually expect that metals get more compact with pressure,” Raty said.

Source: Lawrence Livermore National Laboratory

Explore further: 'Wetting' a battery's appetite for renewable energy storage

Related Stories

'Wetting' a battery's appetite for renewable energy storage

August 1, 2014

Sun, wind and other renewable energy sources could make up a larger portion of the electricity America consumes if better batteries could be built to store the intermittent energy for cloudy, windless days. Now a new material ...

Research and applications of iron oxide nanoparticles

February 26, 2014

From the mysteries of producing red colors in traditional Japanese Bizen stoneware to iron-oxidizing bacteria for lithium ion batteries, Professor Jun Takada is at the forefront of research on innovative iron oxide nanomaterials.

Recommended for you

Long-sought chiral anomaly detected in crystalline material

September 3, 2015

A study by Princeton researchers presents evidence for a long-sought phenomenon—first theorized in the 1960s and predicted to be found in crystals in 1983—called the "chiral anomaly" in a metallic compound of sodium and ...

Probing the limits of wind power generation

September 2, 2015

(Phys.org)—Wind turbine farms now account for an estimated 3.3 percent of electricity generation in the United States, and 2.9 percent of electricity generated globally. The wind turbine industry is growing along all vectors, ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.