Calculations predict unexpected disorder in the surface of polar materials

Research carried out by Dr. Marçal Capdevila-Cortada and Dr. Núria López (ICIQ) reveals the appearance of disordered structures in surfaces that affect their properties. This discovery could help improve the physical and catalytic properties of this type of material. These materials have applications in fuel cells, and are already used in car catalysts to minimize pollutants.

The knowledge of surface structure allows scientists to predict material properties so they can be tuned to specific 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 surface properties is more complex.

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 inclusion of all the complexity in this type of system. Fundamental examples of the role of 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.

More information:
"Enhanced polarity compensation by entropic contributions: the structure of CeO2(100)" M. Capdevila-Cortada and Núria López. Nature Materials, 2016. DOI: 10.1038/NMAT4804

Provided by Institute of Chemical Research of Catalonia (ICIQ)