  We present a numerical investigation of the size scaling of static friction
in incommensurate two dimensional contacts performed for different lateral
loading configurations. Results of model simulations show that both the
absolute value of the force $F_s$ and the scaling exponent $\gamma$ strongly
depend on the loading configuration adopted to drive the slider along the
substrate. Under edge-loading a sharp increase of static friction is observed
above a critical size corresponding to the appearance of a localized
commensurate dislocation. Noticeably, the existence of sublinear scaling, which
is a fingerprint of superlubricity, does not conflict with the possibility to
observe shear-induced localized commensurate regions at the contact interface.
Atomistic simulations of gold islands sliding over graphite corroborate these
findings suggesting that similar elasticity effects should be at play in real
frictional contacts.
