Friday, June 11, 2021

The power of computational materials theory

With the growth of computational capabilities and the ability to handle large data volumes, it looks like we are entering a new era for the global understanding of material properties.  

As an example, let me highlight this paper, with the modest title, "All Topological Bands of All Stoichiometric Materials".  (Note that this is related to the efforts reported here two years ago.) These authors oversee the Topological Materials Database, and they have ground through the entire Inorganic Crystal Structure Database using electronic structure methods (density functional theory (see here, here, here) with VASP both with and without spin-orbit coupling) and an automated approach to checking for topologically nontrivial electronic bands.  This allows the authors to look at essentially all of the inorganic crystals that have reliable structural information and make a pass at characterizing whether there are topologically interesting features in their band structure.  The surprising conclusion is that almost 88% of all of these materials have at least one topologically nontrivial band somewhere (though it may be buried energetically far away from the electronic levels that affect charge transport, for example).  Considering that people didn't necessarily appreciate that there was such a thing as topological insulators until relatively recently, that's really interesting.  

This broad computational approach has also been applied by some of the same authors to look for materials with flat bands - these are systems where the electronic energy depends only very weakly on (crystal) momentum, so that interaction effects can be large compared to the kinetic energy.

The ability to do large-scale surveys of predicted material properties is an exciting development!

1 comment:

Anonymous said...

Very impressive effort!

I personally feel conflicted by this number 88% (or rather ~53%). On one hand this gives evidence that band topology is quite literally all around us, we cannot avoid it. On the other hand, it seems to confirm my own belief that band topology is very rarely relevant and has a tiny set of practical implications.

It would appear that band topology is something akin to the "taste" of a material. In 99% of applicationss, from computers to bridge building, the taste of a material is irrelevant to the application. But in the case of gastronomy it is vital. The question is, will we find this elusive field of topological gastronomy?