NANOTRIBOLOGY (THEORY)
People
P.I. M. Clelia Righi (mariaclelia.righi@nano.cnr.it)
Mauro Ferrario
Seiji Kajita (Toyota Central R&D Lab)
Giacomo Levita
Sophie Loehlé (Total)
Paolo Restuccia
Motivation & objectives.
Research line 1). Understanding fundamental mechanisms of friction and dissipation in nanotribology.
Research line 2). Investigating problems of tribochemistry in systems relevant for practical applications.
Systems.
Research line 1). One of the main difficulties in understanding friction at the microscopic level is the complexity and variety of phenomena that simultaneously take place at the buried sliding interface. For this reason, clean, well defined interfaces represent ideal situations, where simulations can combine with experiments to unravel fundamental aspects of friction. We have recently studied layered materials such as graphene and MoS2 (Fig. 1) and - rare gas adsorbed on metals, with reference to quartz crystal microbalance (QCM) experiments (Figs. 2, 3).
Research line 2). Tribochemical reactions are complex processes occurring at the buried interface in the presence of mechanical stresses, molecular confinement, frictional heating. They are difficult to monitor in real-time by experiments, so simulations can play a very important role here.
We study i) the tribochemistry of solid lubricants interacting with water and ii) prototypical additive molecules at iron interfaces.
Methods.
Research line 1). We use classical molecular dynamics relying on realistic potentials. In particular, the adopted potentials are tested against ab initio calculations in reproducing the shape and corrugation of the interfacial potential energy surface.
Research line 2). Tribochemical reactions are simulated by ab initio molecular dynamics (Car Parrinello or Born Oppenheimer).
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Fig. 1: Potential energy surfaces for the sliding motion of a MoS2 bilayer at zero load (left column) and at 10 GPa load (right column). Unit cells (black lines) and minimum energy paths (red/yellow lines) are reported for completeness. The color scale refers to the energy range of the PES corrugation (in meV) and is reported on the right.
G. Levita, A. Cavaleiro, E. Molinari, T. Polcar, and M. C. Righi, J. Phys. Chem. C 118, 13809 (2014).
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Fig. 2: Equilibrium structure of Kr islands on the Cu(111) surface. The grayscale indicates the particle distance from the minima of the substrate potential.
M. Reguzzoni and M.C. Righi, Phys. Rev. B 86, 245434 (2012).
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Fig. 3: The formation of a new commensurate domain prior to the global slip. The three images are taken at different times during the slip. Red particles are in the original minimum and become blue when they slip into the next minimum. Particles in white are part of the domain wall and are located outside the potential minima.
M. Reguzzoni, M. Ferrario, S. Zapperi and M. C. Righi, PNAS 107, 1113 (2010).
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Fig. 4: Snapshot acquired during an ab initio molecular dynamics simulation of water confined between two diamond surfaces under tribological conditions.
G. Zilibotti, S. Corni, and M.C. Righi, Phys Rev Lett 111, 146101 (2013).
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Publications
Thermolubricity of Xe monolayers on graphene
M. Pierno, L. Bignardi, M.C. Righi, L. Bruschi, S. Gottardi, M. Stohr, P. Silvestrelli, P. Rudolf, and G. Mistura
Nanoscale 8062, 6 (2014)
Sliding properties of MoS2 layers: load and interlayer orientation effects
G. Levita, A. Cavaleiro, E. Molinari, T. Polcar, and M.C. Righi
J. Phys. Chem. C 118, 13809 (2014)
Load-induced confinement activates diamond lubrication by water
G. Zilibotti, S. Corni, and M.C. Righi
Phys. Rev. Lett. 111, 146101 (2013)
Potential energy surface for graphene on graphene: Ab initio derivation, analytical description, and microscopic interpretation
M. Reguzzoni, A. Fasolino, E. Molinari, and M.C. Righi
Phys. Rev. B 86, 245434 (2012)
Friction by shear deformations in multilayer graphene
M. Reguzzoni, A. Fasolino, E. Molinari, and M.C. Righi
J. Phys. Chem. C 116, 21104 (2012)
Static friction by domain coalesce at critical size
M. Reguzzoni and M.C. Righi
Phys. Rev. B (RC) 85, 201412 (2012)
Friction of Diamond in Presence of Water Vapor and Hydrogen Gas. Coupling Gas Phase Lubrication and First Principles Studies
M.I. De Barros-Bouchet, G. Zilibotti, C. Matta, M.C. Righi, L. Vandenbulcke, B. Vacher, and J. M. Martin
J. Phys. Chem. C 116, 6966 (2012)
Onset of frictional slip by domain nucleation in adsorbed monolayers
M. Reguzzoni, M. Ferrario, S. Zapperi, and M.C. Righi
PNAS 107, 1113 (2010)
Ab initio study on the surface chemistry and nanotribological properties of passivated diamond surfaces
G. Zilibotti, M.C. Righi, and M. Ferrario
Phys. Rev. B 79, 075420 (2009)
Pressure induced friction collapse of rare gas boundary layers sliding over metal surfaces
M.C. Righi and M. Ferrario
Phys. Rev. Lett. 99, 176101 (2007)