I will present recent results in the context of the two main research lines carries out by our group i) understanding and controlling tribochemistry processes to advance lubricant additives ii) high-throughput, first-principles calculations of solid interfaces.

i) The functionality of lubricant additives that function in boundary lubrication conditions often relies on the formation of “tribofilms”, the structure and composition of which can largely differ from that of the precursor molecules. Moreover, the process of in situ tribofilm formation, governed by tribochemical reactions, remains often obscure. Ab initio molecular dynamics, eventually linked to Green’s functions [1], constitutes a powerful tool to monitor in real time what happens at the sliding buried interface. I will present an example of application concerning the in situ formation of slippery selenide layers from nanopowders. The results demonstrate an unconventional and smart way to synthesize transition metal dichalcogenide layers in operando and exploit their friction- and wear-reducing impact [2].

ii) We developed a modular workflow, TribChem,[1] connected to publicly available databases, and performed the high-throughput ab initio screening of the adhesion energy of around a hundred metallic heterostructures, ranging from transition to noble metals [2]. The dataset allowed us to identify general trends confirming a correlation of interfacial adhesion and electronic charge already observed for homogeneous interfaces [3]. By using a machine learning approach, we obtained a simple analytical expression for predicting the adhesion energy from the surface energy other intrinsic properties of the two heterostructure constituents alone, which can prove useful for avoiding expensive supercell calculations.

Acknowledgments

These results are part of the ”Advancing Solid Interface and Lubricants by First Principles Material Design (SLIDE)” project that has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant agreement No. 865633).

References

[1] S. Kajita, A. Pacini, G. Losi, N. Kikkawa, and M.C. Righi, Accurate multiscale simulation of frictional interfaces by Quantum Mechanics/Green’s Function molecular dynamics, Journal of Chemical Theory and Computation (2023) doi.org/10.1021/acs.jctc.3c00295.
[2] P. G. Grützmacher, M. Cutini, E. Marquis, M. Rodríguez Ripoll, H. Riedl, P. Kutrowatz, S. Bug, Chia-Jui Hsu, J. Bernardi, C. Gachot, A. Erdemir, and M. C. Righi, Se Nano-Powder Conversion into Lubricious 2D Selenide Layers by Tribochemical Reactions, Advanced Materials, 2302076 (2023).
[3] G. Losi, O. Chehaimi, and M. C. Righi, Tribchem, a high through-put package for solid interfaces, Journal of Chemical Theory and Computation (2023) doi.org/10.1021/acs.jctc.3c00459.
[4] P. Restuccia, G. Losi, O. Chehami, M. Marsili, and M.C. Righi, High throughput accu-rate prediction of interfacial adhesion energies in metal-on-metal contacts, ACS Applied Materials and Interfaces 15, 19624 (2023).
[5] M. Wolloch, G. Levita, P. Restuccia, and M.C. Righi, Interfacial Charge Density and Its Connection to Adhesion and Frictional Forces, Physical Review Letters 121, 026804 (2018).