Writeup from the November 19, 1999, issue of Inside R&D concerning the article entitled "The inverse band-structure problem of finding an atomic configuration with given electronic properties" (A. Franceschetti and A. Zunger, Nature 402, 60, 1999) by Alberto Franceshetti and Alex Zunger.
Materials scientists usually determine the electronic properties of materials with a known atomic configuration. Finding an atomic configuration with given electronic properties sounds like a backwards way of going about the process, but Alberto Franceschetti and Alex Zunger of the National Renewable Energy Laboratory now offer a theoretical solution to this inverse structure problem and say it can actually work better than the standard approach. They describe and demonstrate their method in a recent "Nature". Their approach uses simulated annealing to focus on the configuration that matches the electronic properties, in this case with reference to semiconductor alloys and superlattices. The same algorithm could be applied to many other types of compounds and may lead to the discovery of new materials with electronic and optical properties superior to those currently available. Why did Franceschetti and Zunger take this seemingly counterintuitive tack to materials discovery? Simple: To improve the chances of finding technologically important materials. In fact, the conventional approach to the discovery of new materials having the potential for useful applications follows a rather indirect path, Franceschetti suggests. First you study potentially "interesting" or "promising" materials, and then, when a new property is discovered in these materials, you suggest applications. This is the paradigm followed, for instance, in the discovery of high-Tc superconductors. "Our approach attempts to 'hit the target' by first declaring in advance the properties of interest, within a given class of materials, and then among the astronomical number of structures, finding the candidate structure that has the required properties," says Franceschetti, who characterizes his and Zunger's method as a "theoretical combinatorial chemistry" approach.
In the near term, the NREL scientists plan to apply this technology to the design of semiconductor alloys and heterostructures having pre-assigned optical and electronic properties. For example, there is a demand for materials with superior optical properties that are compatible with current electronic technologies based on silicon.
In the long term, Franceschetti and Zunger plan to extend their method to cover new classes of physical properties, such as transport and photonic properties, and new classes of materials, such as superconductors, ferroelectrics, organic molecules, etc. They are seeking funding from the US DOE.
Copyright 1999, John Wiley & Sons, Inc., New York, NY 10158