Structural models of the reconstructed W{001} surface

A LEED intensity analysis of 5 beams from the low-temperature W{001}c(2×2) structure indicates that the surface reconstruction involves shifts of the surface atoms along 〈110〉 directions within the plane of the surface, as suggested by Debe and King. At temperatures 100-140K the shifts are in the range 0.15-0.3 Å, with the first interlayer spacing 1.48-1.58 Å (bulk value 1.58 Å). Similar analysis of the room-temperature W{001}c(2×2)-H phase indicates: (i) none of the models proposed, which ascribe the c(2×2) structure directly to ordered hydrogen adsorption, can explain the experimental data; (ii) the W{001}c(2×2)-H structure is probably impurity stabilized by H at room temperature in the same W lattice as the low-temperature reconstructed phase. © 1978.