The second layer of Ag on Pt ͑111͒ is experimentally observed to form a striped dislocation pattern with Ag stripes alternating between fcc and hcp stacking. We address the origins of the stripes with a combination of density-functional theory and Monte Carlo simulations. We find that this dislocation pattern is driven by electronic and anisotropic substrate-mediated interactions associated with the Shockley surface state on Ag ͑111͒. Our simulations reveal the quantum mechanical underpinnings of strain-relief patterns, previously described phenomenologically by the classical Frenkel-Kontorova model that is widely used to describe such systems.

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