Atomic-scale design of superlubricity of carbon nanostructures on metallic substrates
Lead Research Organisation:
University of Warwick
Department Name: Chemistry
Abstract
Superlubricity, a state of ultra-low friction, will facilitate a significant reduction of friction-related energy loss and device failure of any moving mechanical device. Given the trend towards miniaturisation of such devices, studies of mechanical properties at atomic scales become ever more important. Developing nanoscale devices exhibiting superlubricity requires a detailed understanding of the fundamental principles governing dynamic sliding friction at an atomic scale. At this scale, particularly at atomically smooth surfaces, friction is governed by electronic and phononic excitations, which may be seen as levers to regulate friction.
The central aim of this project is to computationally investigate the mechanisms of dynamic friction. Explicitly simulating the dynamic friction coefficient associated with interfacial shear requires the development of new atomistic simulation tools that incorporate phononic and electronic frictional dissipation mechanisms. Using these methods, we will study the fundamental mechanisms of frictional energy dissipation in well-defined systems. This will provide new insights into which frictional effects dominate for which system and under which experimentally controllable environment conditions. Our insights and simulation methods will build the groundwork to develop new systems that allow switching friction "on" and "off".
The host is an expert on computational solid-state physics, surface chemistry, modelling of electronic friction and machine learning methods, which ideally aligns with the research goals of this proposal. The researcher will extend his research portfolio to the simulation of dynamic processes at surfaces, MD simulation including non-adiabatic simulations, and energy dissipation. He will further his knowledge on the development of ML methods for dynamics. This will boost his future ability to shape the field of atomistic interface engineering.
The central aim of this project is to computationally investigate the mechanisms of dynamic friction. Explicitly simulating the dynamic friction coefficient associated with interfacial shear requires the development of new atomistic simulation tools that incorporate phononic and electronic frictional dissipation mechanisms. Using these methods, we will study the fundamental mechanisms of frictional energy dissipation in well-defined systems. This will provide new insights into which frictional effects dominate for which system and under which experimentally controllable environment conditions. Our insights and simulation methods will build the groundwork to develop new systems that allow switching friction "on" and "off".
The host is an expert on computational solid-state physics, surface chemistry, modelling of electronic friction and machine learning methods, which ideally aligns with the research goals of this proposal. The researcher will extend his research portfolio to the simulation of dynamic processes at surfaces, MD simulation including non-adiabatic simulations, and energy dissipation. He will further his knowledge on the development of ML methods for dynamics. This will boost his future ability to shape the field of atomistic interface engineering.
Publications
Nam S
(2024)
Exploring in-plane interactions beside an adsorbed molecule with lateral force microscopy
in Proceedings of the National Academy of Sciences
| Description | This project has yielded key insights into atomic-scale friction at organic/inorganic interfaces, by combining density functional theory (DFT), machine learning (ML), and experimental, atomic-scale surface analysis techniques. This enabled us to uncover fundamental mechanisms of energy dissipation. At the atomic scale, energy dissipation is governed by fundamentally quantum-mechanical interactions and is strongly dependent on the local bonding environment as well as external stimuli, such as the temperature. Studying this required the development of theoretical and computational models that can accurately describe these effects. By combining state-of-the-art DFT and ML with experimental validation via lateral force microscopy, we were able to deliver a detailed understanding of how molecular structure and interface properties influence frictional forces. Our work provides fundamental insights into the mechanisms of atomic-scale energy dissipation with substantial future implications for designing tailored surface interactions for applications in catalysis, functional monolayers, and superlubricity. In a collaborative study between experiment and theory, we have explored the in-plane interactions of molecular layers, by combining DFT simulations and lateral force microscopy. This allowed us to probe the interactions beside an adsorbed molecule. The DFT modelling demonstrated that the energy dissipation measured in lateral force microscopy experiments can only be explained if the interaction between the tip dipole and the electrostatic potential of the sample is fully accounted for. This highlights the role of electrostatic interactions in energy dissipation at the nanoscale, providing a more accurate understanding of the dynamics in molecular layers. Our findings facilitate the development of design princelets to tailor intermolecular interactions for applications in catalysis, functional monolayers, and superlubricity. Building on this work, we investigate sliding friction over single covalent bonds that correlate with bond order. For this, we developed an approach to simulate energy dissipation between single atoms, by combining DFT and ML. These theoretical methods were used to demonstrate that energy dissipation between a single atom and a bond between atoms is correlated with the bond order of this bond. Experimental validation was carried out by our collaborators. Moreover, we show that friction over hydrogen bonds and covalent bonds is a result of different mechanisms. This is demonstrated through highly accurate machine-learned potential energy surfaces. |
| Exploitation Route | The outcomes of this project will inform the design and interpretation of future experiments on nanoscale friction at the single-molecule and thin-film level to enhance our understanding of atomic-scale energy transfer processes. |
| Sectors | Chemicals Energy |
| Description | Understanding energy dissipation between single atoms with density functional theory and lateral force microscopy |
| Organisation | University of Regensburg |
| Country | Germany |
| Sector | Academic/University |
| PI Contribution | I am the main theoretical contributor. My work consists of (A) algorithm development to simulate single atom energy dissipation and (B) modelling of single atom energy dissipation at surfaces using time-dependent density functional theory and machine learning. Additionally, I contribute to conceptualisation and planning of research, as well as manuscript writing and editing. |
| Collaborator Contribution | My collaborators, Dr Alfred J. Weymouth and Prof. Franz J. Giessibl, contributed the experiment measurements and analysis. They also contribute to conceptualisation and planning of research, as well as manuscript writing and editing. |
| Impact | This collaboration has worked on several publications, one already being published, one having been submitted recently, and several more that are actively being worked on: - Exploring in-plane interactions beside an adsorbed molecule with lateral force microscopy (published). Here, I lead the theoretical, first-principles modelling, which demonstrated that the energy dissipation measured in lateral force microscopy experiments can only be explained if the interaction between the tip dipole and the electrostatic potential of the sample is fully accounted for. - Sliding friction over single covalent bonds correlates with bond order (submitted) Here I lead the theoretical method development and modelling to demonstrate that energy dissipation between a single atom and a bond between atoms is correlated with the bond order of this bond. Moreover, we show that friction over hydrogen bonds and covalent bonds is a result of different mechanisms. |
| Start Year | 2023 |