New computer model uncovers elusive atomic structure of materials

(01-02-2021)

As next-generation materials for applications in the chemical industry, energy conversion, and more become increasingly complex to meet the stringent industrial requirements, so does their atomic-level structure. This complexity makes it very challenging to exactly identify the structure of experimental samples, especially since scientists rarely have an overview of all structural possibilities. New research from the Center for Molecular Modeling (CMM) at Ghent University levels the playing field by constructing all possible models and ranking them using quantum mechanical calculations, until only the the most likely model remains standing before making our first guess in this convoluted game of “Guess Who?”.

Simply explained

Imagine yourself as the newest supervisor of a building company focused on K’NEX construction... at the nanoscale. Your predecessor succeeded in making a very intricate K’NEX design but subsequently left the company. Your job is to capitalize on this invention by providing step-by-step guidelines of how the different K’NEX building blocks come together to form this promising material and maybe even come up with similar – or even more successful – designs. However, your predecessor left no design instructions at the construction site. The only thing you can base yourself on is a fuzzy photograph of his successful design and the knowledge that K’NEX structures are modular, where individual blocks are combined into a larger structure, leading to an enormous number of possible combinations even with only a few types of blocks. How to find out in which way the different building blocks need to be combined to achieve that revolutionary K’NEX design?

Although fictional, this situation is strangely relatable for material scientists that investigate the construction of modular materials. In these modular materials, rigid building blocks are assembled into periodic patterns on the nanoscale. These materials are incredibly versatile and the structures are very appealing to solve various technological challenges, as appropriate building blocks can be selected for the application at hand, such as energy storage, shock absorption, greenhouse gas capture, or catalysis. However, the sheer number of possible ways in which the building blocks can be combined often makes their characterization arduous. Fortunately, researchers at the Center for Molecular Modeling (CMM) at Ghent University have proposed a protocol to accept this challenge, which is now published in Angewandte Chemie.

Shedding light on the materials’ structure... at the nanoscale

Usually, to describe the atomic-level structure of such next-generation building block materials, scientists start by looking at how the material behaves, and then try to make guesses about its structure. This guessing is often ambiguous and can induce strong biases towards earlier models. In contrast, the new approach completely reverses this workflow. The newly published methodology starts by combining the different building blocks in all different ways, constructing all possible structural models in a computer. This removes the ambiguity in making an initial guess, leading to an easy-to-use, systematic, and reliable workflow. Subsequently, all the models are subjected to quantum mechanical calculations to accurately consider the atoms’ behaviour at the nanoscale, allowing for a comparison between theory and experiment which facilitates a quantitative ranking between the possible models.

These results offer the perspective to resolve the atomic structure of complex materials and understand what makes their design so revolutionary. By using this knowledge, new design principles can be established to build next-generation materials with even better performance, ushering in a new era in material design.