Phase transition on Mo(100) and W(100) surfaces

Low-energy-electron-diffraction studies of carefully cleaned and annealed surfaces of molybdenum (100) and tungsten (100) show that a phase transition can be induced by lowering the temperature below 300 K. The periodicity of the ''reconstructed'' surface is believed to be due to the formation of a displacement wave with a wavelength which is 2a (a is the lattice parameter) for W(100) and approx. 2.2a for Mo(100). The phase transition is reversible and seemingly second order. It appears possible that displacements of this type also occur in chemisorption on these surfaces