Pseudomorphic-to-close-packed transition. II. Application to Ni on Mo(110)

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Abstract
The aim of this investigation is (a) to confirm by numerical quantification of analytical expressions in paper I, involving embedded-atom methods (EAM’s), that a pseudomorphic, rather than a close-packed, Ni monolayer (ML) on Mo{110}, is stable, and (b) to establish the physics of the pseudomorphic-to-close-packed transition. Of the two close-packed configurations identified by a rigid-model approach, the one with incomplete misfit dislocations is shown, using transformed-stiffness constants (intralayer interaction) and EAM-calculated Fourier coefficients (interlayer interaction), to be the stable one with an average energy per Ni atom of 0.297 eV after final relaxation. An EAM calculation, presumably accounting for anharmonicity at 26% of pseudomorphic strain and for substrate proximity, yields the lower value 0.258 eV for the average energy per Ni atom in the pseudomorphic monolayer, and thus confirms the relative stability of the pseudomorphic monolayer. The pseudomorphic-to-close-packed transition–apparently from a lower energy pseudomorphic to a higher energy close-packed configuration–has been explained on kinetic grounds: the rapid formation of the close-packed configuration by penetration of excess atoms under nonequilibrium conditions of growth. Under equilibrium conditions, individual excess atoms reach the ML periphery by surface migration to effect continued pseudomorphic growth.