DFT study of Ni-doped MoS₂ as a solid lubricant for space applications

MoS₂ is a layered material with interesting mechanical properties not unlike graphite. The weak Van der Waals forces between MoS₂ sheets allow the material to be used as a solid lubricant with application in the low temperature and pressure environment in space, where liquid lubricants fail. Some preliminary studies suggest that doping with transition metals can improve tribology performance by reducing friction and wear. We use density functional theory (DFT) calculations to determine the structure and properties of bulk Ni-doped MoS₂, considering formation energy of Ni in different sites as a function of growth conditions, and study the potential energy for sliding to connect to frictional forces measured in atomic-force microscopy (AFM). We calculate vibrations with density-functional perturbation theory (DFPT) for comparison to infrared and Raman spectra in experimental characterization. Our resulting DFT data will be used to parametrize classical force fields for larger-scale reactive molecular dynamics (MD) simulations that can directly address friction and wear.