Physicists use supercomputer to crack 140-year old puzzle

1 point

5 years ago

Since the dawn of civilization, metallurgy has determined the fate of powerful cities, states and empires. Blacksmiths have harnessed the power of heat to melt simple metals that would then be cast into hard, sharp and shiny alloys. By changing process conditions, such as rate of cooling and composition can lead to new materials with dramatically different mechanical properties, such as extreme ductility, ultra-high strength or enhanced magnetism.

In 1879, Nobel-prize winning physical chemist Friedrich Wilhelm Ostwald discovered that liquids often freeze first into temporary (metastable) structures before converting into their final, most stable equilibrium phase. This so-called “Ostwald step rule” has been a fundamental mechanism for the study and synthesis of new materials and is a textbook principle that all physicists learn in school. But the details of how this might occur at the atomic scale have remained a mystery.

In recent <a href="https://www.newswise.com/articles/scientists-shed-light-on-140-year-old-challenge-in-chemistry-and-physics">ground-breaking research</a>, published in the <a href="https://doi.org/10.1073/pnas.2017809118"><i>Proceedings of the National Academy of Sciences</i></a>, Lawrence Livermore National Laboratory scientists report on a new mechanism of freezing that provides an atomistic view of Ostwald’s step rule and alters the fundamental understanding of nucleation at high pressure. By <a href="https://youtu.be/V_MATvJClOg">simulating the motion of the atoms</a> using the NVidia Volta V100 GPUs of the Lassen supercomputer, they found that the crystallization process happens in the way Ostwald observed, but that there are additional new pathways that occur when the pressure is increased. The discovery of these new rules for freezing in metals opens the door to using high pressure to synthesize new types of materials, with unusual properties engineered through high-performance computing.