ENTROPIC STEP DOUBLING ON W(430)

We present high resolution low energy electron diffraction results for the W(430) surface Unlike every other system studied to date, single atomic height steps on this surface become thermodynamically unfavorab le at elevated temperatures, Above 940 K a new phase consisting of bou nd single and double height steps forms. The transition to double heig ht steps is predicted on the basis of a simple model provided that kin ks on the double height steps have a lower formation energy than kinks on single height steps. The ne cv phase is stabilized by a step edge interaction between single-double pairs.