Berkeley Lab Researchers’ Work Paves the Way for Metastable Materials

If you've ever seen a diamond you're already familiar with metastable materials. Increasingly, researchers are looking for ways to identify new metastable materials for technological applications.

We know that when atoms or molecules come together to form a solid, some atomic arrangements are more favorable than others. These different atomic arrangements, known by their crystal structures, each have different energies, and the most favorable crystal structure is the one with the lowest energy. It’s also the most thermodynamically stable structure.

The Materials Project uses the power of supercomputing to provide open Web-based access to computed information on known and predicted materials as well as powerful analysis tools to inspire and design novel materials. (Image source: The Materials Project) 

To date, materials science has primarily focused on the design and engineering of stable structures. However, many materials can exist for extended periods in what’s known as “metastable structures,” which are not the lowest-energy crystalline arrangement, usually because there is a barrier to transforming to a more stable form.

Some metastable structures can be technologically useful. Diamonds, which are a metastable arrangement of carbon atoms (the stable form is graphite), have spectacular properties, including high hardness and thermal conductivity (and they’re also quite pretty). Increasingly, researchers are looking for ways to identify other useful metastable materials.

Researchers from the Department of Energy's (DOE) Lawrence Berkeley National Laboratory are forging a path toward an easy way to design and create promising next-generation materials for use in everything from semiconductors to pharmaceuticals to steels, according to Wenhao Sun, one of the researchers on the project.

The research was published last month in the journal Science Advances .

“The first step to designing new metastable materials is to understand the differences in energy between metastable structures and their stable structures,” Dr. Sun told Design News . “And that is what our study aimed to do. We measured the thermodynamic scale of metastability for all known inorganic solids, by a large-scale data-mining of our computed materials property database, named the Materials Project.”

Because investigations of metastable materials have been limited to date, and the information that did exist was scattered, materials scientists have had a relatively poor understanding of which material chemistries and compositions can be metastable, and how metastable they can be. Sun calls the new research a way to begin “building intuition” when it comes to metastable materials.

“By studying the metastability of existing materials, we can better predict which new metastable materials can be made,” he said. “Our data-mining study revealed some new trends in metastable materials, that could be used to help a materials designer estimate whether a predicted metastable material could be made or not.”

Thanks to quantum-mechanical methods used to directly compute materials properties, the team was essentially able to calculate the properties of all known inorganic materials. The calculated properties are put into extremely large databases – the Materials Project being one – and this enables the team to make very broad and general observations about metastability.

A better understanding of metastability will open many new avenues in materials science. While metastability in materials like steel are better understood because steel has a long history of being engineered for new properties, the new knowledge can help materials researchers

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