High Density Sliding at Ta/Al and Al/Al Interfaces

We present 3D-NEMD results for the velocity dependence of the frictional force at smooth and roughened interfaces for Ta and Al single crystals. For Ta/Al we consider Ta (100)/Al (100) and Ta (110)/Al (111) interfaces sliding along [001] and $[1\mathop 1\limits^- 0]_{fcc} /[001]_{bcc} $ respectively. These are compared with Al (111)/Al (100) interfaces at the same loads, corresponding to a pressure of 15 GPa. Both interfacial pairs show similar behavior in the velocity dependence of the frictional force: a low velocity regime with an increasing frictional force, followed by a strain induced transformation regime at velocities above approximately 1/10 the transverse sound speed, followed by a fluidized interface at high velocities. For both interfacial pairs, the high velocity dependence of the frictional force exhibits power law behavior, v$^{-\beta }$, with $\beta $ = 3/4. We discuss the structural changes that influence dissipation in these regimes.