Calculations predict unexpected disorder in the surface of polar materials
The small units that constitute materials are ordered in their surfaces. The knowledge of the surface structure allows scientists to predict their properties so they can be tuned to our needs. Nevertheless, reality is more complex. The group of Professor Núria López at ICIQ in Catalonia has found, through massive simulations, that in certain surfaces disorder is intrinsic and therefore the prediction of these surface properties is more complex. Calculations (more than 50000 simulations) were carried out on the Mare Nostrum supercomputer at the Barcelona Supercomputing Center. In this case, simulations are essential, since they allow the introduction of all the complexity in this type of systems. Fundamental examples of the role of disorder (or entropy) are also present in other areas of chemistry, physics and biology. In fact, our own brains are designed to recognize patterns and symmetries, thus making the understanding of disorder challenging.
Now, the work published by ICIQ researchers details why and how atoms are ultimately ordered in polar surfaces. Based on the configurational entropy concept, scientists classified different surface rearrangements according to their stability. They have also demonstrated that these surfaces are dynamic and the rearrangements are interchangeable. The new terminations show different patterns on the materials surface, affecting their mechanical and catalytic properties and their properties as sensors. These properties are fundamental to decrease energy consumption and attain greener and sustainable processes towards a circular economy.
"Enhanced polarity compensation by entropic contributions: the structure of CeO2(100)" M. Capdevila-Cortada and Núria López. Nat. Mater., 2016, DOI: 10.1038/NMAT4804