Periodic Reporting for period 2 - SLIDE (Advancing Solid Interfaces and Lubricants by First Principles Material Design)
Période du rapport: 2022-05-01 au 2023-10-31
Friction and wear have massive energy environmental costs. By improving the tribology technologies, a huge amount of energy could be saved, with consistent reduction of fuel consumptions and carbon dioxide emissions. These technologies are nowadays fully based on materials, thus great efforts should be made to understand the physics and chemistry that rule the frictional behavior of surfaces in contact. This is not an easy task as friction is governed by atomistic processes that occur at the sliding buried interface, which is very difficult to monitor in real time by experiments. Simulations can play a crucial role here, in particular those based on a quantum mechanical approach, which is essential for an accurate description of the conditions of enhanced reactivity imposed by the mechanical stresses applied.
The goal of SLIDE is to port the material design paradigm based on First Principles Material Discovery to the field of Tribology by the development and applications of i) a protocol for harnessing tribochemical reactions to reduce interface friction. SLIDE will focus, in particular, in the development of environmental- friendly alternatives to commercial additives used in engine oils; ii) a workflow for high throughput screening of solid interfaces. A public database for the intrinsic adhesion and shear strength of a wide number of materials pairs will be created. Such database will constitute a source of realistic parameters for continuum models, paving the way for serial multiscale approaches to tribology, from the electronic- to the macro scale.
The goal of SLIDE is to port the material design paradigm based on First Principles Material Discovery to the field of Tribology by the development and applications of i) a protocol for harnessing tribochemical reactions to reduce interface friction. SLIDE will focus, in particular, in the development of environmental- friendly alternatives to commercial additives used in engine oils; ii) a workflow for high throughput screening of solid interfaces. A public database for the intrinsic adhesion and shear strength of a wide number of materials pairs will be created. Such database will constitute a source of realistic parameters for continuum models, paving the way for serial multiscale approaches to tribology, from the electronic- to the macro scale.
The progress made in the period covered by the report in achieving the two objectives outlined above are summarized in the following.
We developed a Python-based program, Xsorb, to automatically identify the accurate adsorption energy and geometry of complex molecules on crystalline (reconstructed) surfaces. Xsorb has been released in a public GitLab repository https://gitlab.com/triboteam/xsorbed/(s’ouvre dans une nouvelle fenêtre)
The adsorption and dissociation of MoDTC, ZDDP, aromatic molecules, and hydrocarbons/polymers were calculated and the effects of surface oxidation on the tribochemistry of MoDTC and ZDDP were studied by combined DFT calculations and experiments. The interaction of molecules present in the environment, such as H2O, O2, and H2, with diamond, phosphorene, and MXenes was also considered.
The effects of uniaxial compression on dissociation were investigated for MoDTC, ZDDP, and hydrocarbon molecules. Fully ab initio molecular dynamics (AIMD) simulations of sliding interfaces uncovered the mechanisms of the tribologically-induced formation of lubricious MoS2 layers from MoDTC molecules, graphene from aromatic molecules, and 2D selenide layers from Se nanopowder. The effects of surface oxidation on the tribological behavior of carbon-based films, MoS2, and Mxenes, were also studied.
A multiscale code that links AIMD with Green’s function MD was presented in a publication, which includes an example of application to diamond films with different passivation.
ii) We released TribChem, a software for high throughput calculations, which includes modules (sub WFs) for surface matching, calculation of the interfacial adhesion, and shear strength. The source code and user manual have been deposited in a public repository https://gitlab.com/triboteam/tribchem(s’ouvre dans une nouvelle fenêtre).
TribChem was applied to populate a database for the interfacial adhesion of metallic heterostructures, which was then analyzed through machine learning. The interlayer adhesion of MXenes with different terminations was calculated, as well as the adhesion of different layered materials on (oxidized) metallic substrates. Heterointerfaces relevant to the triboelectric effect were also considered. A database for chemisorption on metallic surfaces was generated and the effects of adatom intercalation on the adhesion of homogeneous interfaces were identified.
We developed a Python-based program, Xsorb, to automatically identify the accurate adsorption energy and geometry of complex molecules on crystalline (reconstructed) surfaces. Xsorb has been released in a public GitLab repository https://gitlab.com/triboteam/xsorbed/(s’ouvre dans une nouvelle fenêtre)
The adsorption and dissociation of MoDTC, ZDDP, aromatic molecules, and hydrocarbons/polymers were calculated and the effects of surface oxidation on the tribochemistry of MoDTC and ZDDP were studied by combined DFT calculations and experiments. The interaction of molecules present in the environment, such as H2O, O2, and H2, with diamond, phosphorene, and MXenes was also considered.
The effects of uniaxial compression on dissociation were investigated for MoDTC, ZDDP, and hydrocarbon molecules. Fully ab initio molecular dynamics (AIMD) simulations of sliding interfaces uncovered the mechanisms of the tribologically-induced formation of lubricious MoS2 layers from MoDTC molecules, graphene from aromatic molecules, and 2D selenide layers from Se nanopowder. The effects of surface oxidation on the tribological behavior of carbon-based films, MoS2, and Mxenes, were also studied.
A multiscale code that links AIMD with Green’s function MD was presented in a publication, which includes an example of application to diamond films with different passivation.
ii) We released TribChem, a software for high throughput calculations, which includes modules (sub WFs) for surface matching, calculation of the interfacial adhesion, and shear strength. The source code and user manual have been deposited in a public repository https://gitlab.com/triboteam/tribchem(s’ouvre dans une nouvelle fenêtre).
TribChem was applied to populate a database for the interfacial adhesion of metallic heterostructures, which was then analyzed through machine learning. The interlayer adhesion of MXenes with different terminations was calculated, as well as the adhesion of different layered materials on (oxidized) metallic substrates. Heterointerfaces relevant to the triboelectric effect were also considered. A database for chemisorption on metallic surfaces was generated and the effects of adatom intercalation on the adhesion of homogeneous interfaces were identified.
The studies on tribochemical processes are particularly relevant as they allowed us to describe in real time novel phenomena difficult to be observed by experiments. Most of the tribochemistry studies are based on empirical force-fields (FFs), the accuracy of which is often questionable. We have proven AIMD to be a very powerful tool to accurately describe tribochemical phenomena, such as the tribologically-induced formation of lubricious MoS2 layers from MoDTC molecular additives, which has been longley debated in the tribology community. Our simulations are relevant not only for applications, but also for fundamental understanding the mechanical activation of structural phase transitions. The results obtained on the tribologically-induced formation of graphene from aromatic molecules are also very promising for the design of novel lubricant materials not harmful for the environment. We also demonstrated an unconventional and smart way to synthesize bidimensional materials by sprinkling selenium nanopowders onto a tribological contact. The in operando synthesis of lubricious layers by stress-assisted chemical reactions is accompanied by a drop of the friction coefficient, which was measured by experiments.
ii) For the first time to our knowledge, we apply first principles high throughput calculations to tribology. The advanced software we produced, TibChem, is able to screen hundreds of solid interfaces in an automatized way and store the results in a database. The software can be used by non-experts and thanks to its modular structure can be extended to study several interfacial properties.
The database we produced on the adhesion of metals is being extended to covalent/metallic interfaces and constitutes a source of realistic parameters for continuum mechanics models. Moreover, with the aid of machine learning algorithms, general trends have been identified among the data and predictive models for interfacial adhesion have been developed.
ii) For the first time to our knowledge, we apply first principles high throughput calculations to tribology. The advanced software we produced, TibChem, is able to screen hundreds of solid interfaces in an automatized way and store the results in a database. The software can be used by non-experts and thanks to its modular structure can be extended to study several interfacial properties.
The database we produced on the adhesion of metals is being extended to covalent/metallic interfaces and constitutes a source of realistic parameters for continuum mechanics models. Moreover, with the aid of machine learning algorithms, general trends have been identified among the data and predictive models for interfacial adhesion have been developed.