This picture shows the potential energy surface between layers of molybdenum disulfide (MoS2) obtained from quantum chemical calculations. MoS2 is a layered material with a low friction coefficient and is widely used as a solid lubricant. We use the information obtained from this potential energy surface to relate the frictional behaviour of MoS2 to its atomic-level surface properties. The blue spots in this picture represent low-energy structures and the yellow, orange, and red regions correspond to high-energy structures.