Forward-electron-scattering study of the surface structure and phase transition on W(001)

Forward-electron-scattering measurements are used to investigate the surface structure and temperature-driven phase transition at the W(001) surface over the 100--770 K temperature range. Structural parameters obtained for the c(2×{}2) low-temperature phase, T280 K, are compatible with the Debe-King zig-zag chain model, but the temperature dependence of local surface structure deduced from forward-scattering measurements eliminates the possibility of a displacive transition to the (1×{}1) high-temperature phase as suggested by the interpretation of recent helium-atom-scattering experiments.