Temperature dependence of the step free energy - art. no. 073402

We have derived an expression for the step free energy that includes the us ual thermally induced step meandering term and a vibrational entropy term r elated to the step edge atoms, The latter term results from the reduced loc al coordination of the step atoms with respect to the terrace atoms and was introduced recently by Frenken and Stoltze as well as by Bonzel and Emundt s. Additionally, we have added third and fourth terms that deal with the vi brational entropy contribution of the thermally generated step and kink ato ms. At elevated temperatures the two latter vibrational entropy terms are o f the same order of magnitude. Incorporation of these vibrational entropy t erms results in a faster decrease of the step free energy with increasing t emperature than anticipated previously. This enhanced temperature dependenc e of the stop free energy results in a lower thermal roughening temperature of the facet.