Interfacial friction is an extremely common form of interaction between materials in the field of material science. It is well known that hydrogenation or environmental passivation can influence the frictional performance of amorphous carbon coatings. However, the atomic-scale friction mechanisms at clean, unpassivated amorphous carbon interfaces remain insufficiently understood. The primary reason is the experimental observation and conventional friction theories have difficulty in describing the atomic-scale dynamics in non-periodic amorphous systems. Here, we employ a machine learning-based Deep Potential model and Quantum Thermal Bath method to achieve first-principles accuracy in studying the atomic-scale frictional behavior of amorphous carbon interfaces. The simulated friction is qualitatively similar to some experimental findings. By analyzing atomic-scale bond dynamics, we develop a phenomenological friction model that quantitatively describes the microscopic sliding friction at the unpassivated amorphous carbon interface. We further demonstrate that increasing temperature suppresses sliding friction in this system. And an ultralow-friction state can be approached at extreme temperatures (~2000 ℃). This work establishes a universal, structure-independent model bridging atomic simulations with friction model, offering insights into designing low-friction materials.

Refractory high/medium entropy nitrides (HENs/MENs) exhibit comprehensive application prospects as protective films on mechanical parts, particularly those subjected to sliding contacts at elevated temperatures. In this study, a new MEN system TiNbWN, forming a single fcc solution, is designed and its wear performance at temperatures ranging from 25 to 750 °C is explored. The wear mechanisms can be rationalized by examining the subsurface microstructural evolutions using the transmission electron microscopy as well as calculating the phase diagrams and interfacial adhesion behavior employing calculation of phase diagram (CALPHAD) and density functional theory (DFT). To be specific, increased wear losses occur in a temperature range of 25–600 °C, being predominantly caused by the thermally-induced hardness degradation; whereas at the ultimate temperature (750 °C), the wear loss is refrained due to the formation of nanocrystalline oxides (W_nO_3n−2, TiO₂, and γTiO_x), as synergistically revealed by microscopy and CALPHAD, which not only enhance the mechanical properties of the pristine nitride film, but also act as solid lubricants, reducing the interfacial adhesion. Thus, our work delineates the role of the in situ formed nanocrystalline oxides in the wear mechanism transition of TiNbWN thin films, which could shed light on the high-temperature wear behavior of refractory HEN/MEN films.