pilot case 1 – Computational protocol for friction and tribochemistry

(Key person: M.C. Righi, CNR mcrighi@unimore.it)

Understanding and control of friction are key topics in manufacturing and in any application with parts in relative motion, with huge implications, e.g. in the automotive sector, where friction causes the loss of about 70% of the fuel overall energy output.

The technologies nowadays available to reduce friction are based on materials, such as solid and liquid lubricants and hard coatings. The functionality of these materials is deeply affected by chemical processes occurring at the sliding buried interface, which modify the chemical composition of the surfaces in contact with consequent modifications of their adhesion and resistance to sliding.

We release a computational protocol to calculate from first principles the adhesion and resistance to sliding of solid interfaces. These properties are ruled by the physical/chemical interactions between the surfaces in contact that can be accurately described by first principles calculations based on Density Functional Theory (DFT).

We implemented the computational protocol as an Aiida workflow (WF) that allows to obtain adhesion and shear strength in a high throughput way. The software we produced is thought for non-specialized users, with a simplified input file and most computational parameters set automatically to optimized values within the WF.

A schematic representation of the WF is offered above: It is constituted of four principal units U1-U4 (blue rectangles) devoted to the calculation of the bulk, surface, interface and tribological properties. Three functions F1-F3 (red circles) generate the atomic structures to be used in the U1-U3 units. The results produced by each unit are indicated with green circles, among them those stored in a database are indicated by filled circles. The provenance of each data stored in the database is preserved.