- molecules and nanoscale objects on surfaces, especially in the context of friction, and

- gases and liquids of various levels of complexity.

We employ computational as well as analytical methods to solve applied and fundamental problems. We collaborate with experimental as well as theoretical researchers from a wide variety of fields, ranging from chemical engineering to mathematical physics. More details below.

This research subgroup is part of the Materials group at the Department of Mechanical and Industrial Engineering at the Norwegian University of Science and Technology (NTNU)

**Astrid de Wijn**,

Associate professor.

**Faezeh Pousaneh**

Postdoc, NTNU. Statistical mechanics and transport properties of complex fluids.

**David Andersson**

PhD student, NTNU/SU. Simple models for friction of electrolyte systems.

**Robin Vacher**

PhD student, NTNU/SINTEF. Atomistic molecular-dynamics simulations of friction and wear of polymers. Together with Sergio Armada (SINTEF).

**Herman Ferre**

Master student, NTNU. Brake Squeal and earthquakes. Joint supervision with Bjørn Haugen.

**Sindre Flood**

Project student, NTNU. Analysing data on ski friction with machine learning approaches. Joint supervision with Martin Steinert.

- The materials group lunch seminar schedule.
- Molecular Mechanisms in Tribology, Beilstein Nanotechnology Symposium, Potsdam, Germany (2 - 4 October 2018).
- Long Nordita Program: Current and Future Trends in Stochastic Thermodynamics at Nordita in Stockholm, Sweden (4 - 29 September 2017).
- Faraday Discussion: Chemical Physics of Electroactive Materials in Cambridge, UK (10 - 12 April 2017).
- COST action MP1303: Understanding and Controlling Nano and Mesoscale Friction.
- LifeX Gemini Centre: LIFEtime eXtension of metallic structures.
- Nano@NTNU.

One of the main reasons why friction is such a challenging subject, is because many different effects occur at different scales. While two sliding surfaces appear flat on macroscopic scales, they are in fact almost never truly flat (see figure). On smaller scales, the roughness of the surfaces means that the actual contact area is small compared to the apparent contact area. The actual contacts are of the order of micrometer in size. Energy is dissipated in a variety of ways at these contacts by atomic interaction that occur on the scale of a nanometer. To understand friction on large, macroscopic scales, we must first understand friction on micro and nanometer scales. (The study of friction on very small scales is called nanotribology.) During the last few decades, there have been enormous developments in experimental techniques for probing friction on small scales, such as the atomic force microscope (AFM), but theoretical understanding is lagging behind. Theoretical techniques have also undergone developments: the mathematical understanding of dynamical systems as well as the massive increases in computing power have handed us the tools we need to finally understand friction. In our group, we study and model friction on this basic level.