Effect of temperature on single asperity contact and separation in Au

We performed a series of molecular dynamics simulations of contact and separation of two Au surfaces at different temperatures. The pull-off force decreases monotonically with increasing temperature except for an abrupt rise that occurs between T1 ⩽ T ⩽ T2. This abrupt rise can be traced to a series of phase transformations in the sample during separation (face-centered cubic (fcc) → hexagonal close-packed → fcc) at elevated temperatures. The new fcc structure has a lower Schmid factor than the original fcc structure and consequently exhibits higher tensile strength.