Alexandre Tkatchenko, Professor of Condensed Matter Physics at the Faculty of Science, Technology and Communication, publishes a research article in Science, one of the most important multidisciplinary journals in the world.

The true nature of van der Waals forces

Entitled “Wavelike charge density fluctuations and van der Waals interactions at the nanoscale”, the paper focuses on the omnipresent attraction forces between molecules and materials called “van der Waals forces”. Many material properties strongly depend on the strength of these forces. For example, many medicines work because the drug molecules bind in our cells due to selective van der Waals attraction.

A team of researchers, led by Prof. Alexandre Tkatchenko, demonstrated that the true nature of these forces differs from conventional wisdom in chemistry and biology. The scientists showed that these interactions have to be treated as coupling between waves rather than as mutual attraction between particles. “In the simplest case, you can think of two chains of atoms and you could identify points in these chains that are attracted to each other. Typically, you would compute the van der Waals energy by just summing up all these pairs,” explains Alexandre Tkatchenko. “However, we demonstrated that at realistic distances between nanoscale materials this is not true, and instead of particles you have to view them as waves. This drastically affects the way we think about these omnipresent interactions.”

Caption: Treating van der Waals interactions as coupling between waves is a paradigm shift for chemistry and materials science © University of Luxembourg

The article is the result of an international and multi-disciplinary collaboration among four research institutions (Fritz Haber Institute, University of Padova, Cornell University, and University of Luxembourg). “This work provides both a qualitatively correct conceptual framework for describing van der Waals forces at the nanoscale as well as a quantitatively accurate computational framework for predicting how these ubiquitous interactions influence the physical and chemical properties of matter,” adds Robert A. DiStasio Jr., Assistant Professor of Chemistry and Chemical Biology at Cornell University (USA) and one of the lead co-authors of the study.

Impact on material science

The research is likely to have an important impact on material science. Over the last two decades, scientists managed to change the properties of existing materials by incorporating nanomaterials, for example they enhanced stress response or introduced novel conductivity features of polymer composites. “In order to understand all the properties of such nanocomposites you have to comprehend how they self-assemble at the nanoscale. The assembly of these materials is mainly driven by van der Waals interactions,” Prof. Tkatchenko says.

As van der Waals forces are critical for many industrial applications, such as the manufacture of nanocomposites, this work could have a great impact on the refinement of processing techniques in that area. “The present work provides important insights into the forces acting on the nanoscale, with the potential to better understand and tune nanomaterials, specifically nanocomposites, which are ubiquitous in innovative materials applications. Also, specific fields of nano additive manufacturing, nano toxicology, but also nano particle engineering might well take advantage of this ground-breaking work,” comments Prof. Jens Kreisel, Director of the Materials Research and Technology department at the Luxembourg Institute of Science and Technology (LIST).

Exceptional recognition

This publication represents an exceptional recognition for the physicist: “This is a nice culmination of a decade of work. The acceptance rate of papers in Science journal is only around 7%, so I am very proud to be part of this experience,” says Alexandre Tkatchenko delightedly.

For the first time, a researcher from the University of Luxembourg is the lead author in an article published in Science. This highlights the increasing visibility of the University of Luxembourg on the international stage.