Friction through reversible jumps of surface atoms

Area of Science:

• Surface science
• Tribology
• Materials science

Background:

• Nanoscopic friction is crucial for understanding material wear and performance.
• Previous models often simplified the role of atomic motion in friction.
• Experimental friction force microscopy (FFM) shows complex temperature dependencies.

Purpose of the Study:

• To develop a microscopic model for nanoscopic friction.
• To investigate the role of thermally activated surface atom motion.
• To explain the nonmonotonic temperature dependence of friction observed in experiments.

Main Methods:

• Development of a microscopic model incorporating atomic jumps.
• Computational simulations of tip-sample interactions.
• Analysis of energy dissipation during atomic motion.

Main Results:

• Identified two competing processes governing stick-slip motion: jumps to the tip (inhibiting sliding) and jumps back to the sample (enabling sliding).
• Demonstrated that energy dissipated during reversible atomic jumps significantly contributes to friction.
• Showed a nonmonotonic dependence of friction on temperature, consistent with FFM experiments.

Conclusions:

• The proposed model provides a physical basis for microscopic instabilities in friction.
• Thermally activated surface atom motion is a key factor in nanoscopic friction.
• The model successfully explains experimental friction behaviors across various materials.