The transition between the a(1 × 3) and c(4 × 4) surface reconstructions of InSb(001) has been carefully monitored by reflection high energy electron diffraction as a function of temperature and Sb2 flux, without incident In flux. Arrhenius-like behaviour is observed across the whole range of Sb2 fluxes and temperatures, allowing accurate internal calibration of substrate temperature. This behaviour is in contrast to aggregated data obtained under dynamic molecular beam epitaxy conditions, which show two regimes rather than a single Arrhenius-like phase boundary. The results are explained qualitatively by the atomistic kinetics in static versus dynamic conditions.