Berkeley Lab researchers (from left) Kristin Persson, Gerbrand Ceder and Wenhao Sun used the Materials Project to reach a new understanding of metastable materials. Credit: Marilyn Chung, Berkeley Lab
Data-mining used to quantify thermodynamics for nearly 30,000 materials. They say diamonds are forever, but diamonds in fact are a metastable form of carbon that will slowly but eventually transform into graphite, another form of carbon. Berkeley Lab has now quantified the thermodynamic scale of metastability for almost 30,000 known materials. This paves the way for designing and making promising next-generation materials for use in everything from semiconductors to pharmaceuticals to steels. “There’s a great amount of possibility in the space of metastable materials, but when experimentalists go to the lab to make them, the process is very heuristic – it’s trial and error,” said Wenhao Sun. “What we’ve done in this research is to understand the metastable phases that have been made, so that we can better understand which metastable phases can be made.”
The study involved large-scale data mining of the Materials Project, which is a Google-like database of materials that uses supercomputers to calculate properties based on first-principles quantum-mechanical frameworks. Kristin Persson calculated properties of more than 67,000 known and predicted materials with the goal of accelerating materials discovery and innovation.
Metastable materials, or materials that transform to another state over a long period of time, are ubiquitous in both nature and technology and often have superior properties. Chocolate, for example, is metastable, with a lower melting point and better texture than stable chocolate. There are also metastable steels that have both toughness and strength, properties not normally found simultaneously in most stable steels.
Scientists would love to develop new materials with certain properties for various applications – an ultra-strong yet lightweight metal for vehicles etc – but to make any new material with desired properties, materials scientists must understand how synthesizing the material influences its structure, and then how the structure in turn affects its properties and performance. This, Sun explains, is the fundamental paradigm of materials science.
Metastable materials come in many forms, spanning metal alloys and minerals to ceramics, salts, and more, making a comprehensive survey difficult. “What we’ve done is large-scale data mining on nearly 30,000 observed materials to explicitly measure the thermodynamic scale of metastability, as a function of a wide variety of parameters, like chemistry and composition, which inorganic chemists and materials scientists can use to build intuition,” Sun said.
Based on their observations, the researchers went a step further, to propose a new principle they term “remnant metastability” to explain which metastable materials can be synthesized and which cannot. “We’re essentially proposing search criteria¬?we’re identifying which crystalline materials can be made, and possibly under what conditions they can be made,” Sun said. “We hope this can be a more refined way to think about which crystal structure nature chooses when a material forms.” http://newscenter.lbl.gov/2016/11/18/new-understanding-metastability-clears-path-next-generation-materials/
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