04 June 2024

There is an enormously growing demand for materials capable of withstanding extreme conditions, in particular advanced hard and highly electrically conducting materials.

Ferenc Tasnádi and Florian Trybel. Olov Planthaber

Recently, Florian Trybel and Ferenc Tasnádi from IFM have computationally described the properties of new tungsten nitride phases which can be classified as ultra-incompressible superconductors. The W2N3 and W3N5 materials were synthesized by experimental collaborators (see press release here) at extreme pressure and temperature conditions in diamond anvil cells. The materials feature extremely high incompressibility with bulk moduli >350 GPa, calculated hardness values of 30 GPa and superconducting transition temperatures of ~10 K. Both materials are recoverable to ambient conditions and stable in air.

“This finding is a large step towards new industrially relevant materials that shine in applications requiring both high hardness and good electrical conductivity. Their discovery provides another example of how extreme conditions can give unique access to multi-functional materials that have otherwise not been found.”says Florian Trybel, leading the theory team.

Ferenc Tasnádi added “This is yet another example of challenging tasks where advanced supercomputers can help us to understand complex properties. We see more and more how results from high-pressure science and technology teach us new science and open up new dimensions to advance our computational capabilities.”

 

Theoretical Background

Extreme conditions

Conditions that are measured in gigapascal pressure (GPa) and thousands of degrees. For example the center of our planet is at about 365 GPa and 5500°C. This corresponds to millions of times the atmospheric pressure. Extreme conditions allow the synthesis of new materials with new chemistry and outstanding properties. However, bringing these materials back to atmospheric pressure with the same properties is still a big challenge.

Compressibility

Is the ability of a material to withstand hydrostatic compression. Incompressibility can be understood as the ability of a material to withstand a uniform volume reduction created by the same force per area acting on all sides of the material. Diamond has the highest known incompressibility —described by the bulk modulus K—  with a value of K > 440 GPa. Materials with values > 300 GPa are often called ultra-incompressible.

Hardness

Is the ability of a material to resist local plastic deformation. It is usually measured by indenting the material with a diamond and measuring the force necessary to create a “hole” or ”crack”. Here, the hardness was obtained from density functional theory based calculations as the synthesized samples are so far too small to measure their hardness

Superconductivity

A material in a superconducting state shows no electrical resistance (among other properties), which allows, e.g., storage and transport of energy with nearly zero loss. This state is usually achieved by cooling materials to very low temperatures. However, the need for strong cooling restricts possible applications and finding higher temperature or even room-temperature superconductors is a large area of research.

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