Multiscale dynamics

We developed a multiscale approach based on linked ab initio and Green’s function molecular dynamics, which is above the state-of-the-art techniques used in computational tribology as it allows for a realistic description of both interfacial chemistry and energy dissipation through phonons propagation in the semi-infinite bulks in contact. A pictorial representation of this hybrid scheme and its application to a prototypical tribochemistry system (water confined within diamond slabs) is offered in panel a of the figure below. The innermost part of the interface is described by quantum mechanics (QM), to account for the chemical interactions between the two surfaces in contact and the enhanced reactivity of confined molecules. The outermost part of the interface, composed by two macroscopic solids, is described by Green’s function (GF) MD, able to realistically reproduce the vibrational and elastic properties. In panel b, the workflow of the multiscale software is presented: i) The model for the bulk crystal is constructed; ii) the force matrix used to calculate the Green’s function is obtained by static first principles calculations; iii) The QM and GF systems are finally coupled via an add-remove scheme.