Materials science is currently enjoying a golden age, due to the increase in understanding of the underlying atomic phenomena. Studying materials at high pressure is of relevance for everything from coatings of industrial tools to the very fabric of Earth’s inner core. If we understand how matter works at high pressure, we will be in a better position to develop materials that withstand extreme conditions.
In collaboration with experimentalists, researchers in the applied community Electronic Structure recently discovered a new phenomenon in the metal osmium when subjected to ultrahigh pressure. Osmium is the most dense of all elements, with its hardness rivalling that of diamond. It is being used in fountain pen nibs, electrical contacts and other applications where extreme hardness is required. While subjecting an osmium sample to the record-high pressure of four million atmospheres, measurements indicated an anomaly in the relation between the interatomic distances.
In order to understand its origin, SeRC theoreticians performed highly precise simulations of the electronic structure – an effort which required millions of core-hours to reach the required precision. Astonishingly, the anomaly could not be attributed to any reconfiguration of the valence electrons (see figure 11). Instead, it was found that even the innermost electrons begin to interact with each other, a phenomenon never witnessed before. The phenomenon means that we can start searching for brand new states of matter. It opens up a whole box of new questions for future research, and the research results were published in the highly ranked journal Nature.
New simulation tools are currently being developed. The SeRC environment allows material scientists to coordinate their needs with the core communities, and take advantage of large-scale parallel resources. Such coordinated efforts will be essential to study technologically relevant materials at extreme conditions.
Figure. Valence electron constant energy surface (Fermi surface) of osmium. Properties of metals can be related to the valence electrons, which are responsible for bonding. However, accurate calculations show that the structural anomaly at high pressure could not be attributed to any qualitative recon guration of the valence electrons. (Picture courtesy of Q. Feng)