Rotational motion of PF3 molecules adsorbed on Ru(001) is hindered by
other molecules adsorbed on near-neighbor sites. In the limit of very
strong hindrance of relation, a neighboring molecule pair is considere
d to rotate like gears engaged with each other. The distribution of az
imuthal orientation is obtained with the gear network model. The tempe
rature and coverage-dependence of the angular distribution agrees qual
itatively with the results of ESDIAD measurements. (C) 1997 Elsevier S
cience B.V.