THE (1X2) MISSING-ROW PHASE OF AU(110) - ENERGETICS DETERMINED FROM AN EXTENDED EMBEDDED ATOM METHOD

The genesis of order in the missing-row phase of the Au(110) surface and the disordering of that phase have been investigated via examination of the underlying static energetics. We determined the total cohesive energy of various clusters of Au "adatoms" on an Au(110) surface and that of various extended defects on the surface using the embedded atom method with an extension to improve the accuracy of treatment in regions where charge density gradients are large. From the energetics of the clusters we have extracted lattice-gas "adatom-interaction" parameters and studied the resulting disordering phase transition using transfer-matrix scaling. We find Tc = 670 K, in reasonable agreement with experiment. (Experimental Tc's reported range from 650 to 770 K.) From our study of the energy of steps on the (1 × 1) surface and roughening excitations of the reconstructed surface two important results emerge: the energy of steps whose edges are parallel to the rows is very small suggesting the latter play an important role in initiating ordering; certain defects which roughen the (1 × 2) surface are also found to be low in energy, suggesting that the disordering transition includes intrinsic roughening. © 1990.