Neutron diffraction investigation of water on MgO(001) surfaces, from monolayer to bulk condensation

The structure of D 2O molecules adsorbed on MgO(001) surfaces has been studied by neutron diffraction within the 200–273 K temperature range and at coverages ( θ) of 0.93, 1.5, 4 and 20 monolayers (ML). At low coverage ( θ≤1.5 ML) and whatever the temperature, the two-dimensional (2D) analysis of the monolayer structure is compatible with the previously observed p(3×2) commensurate phase, but presenting a short coherence length of 35±5 Å. At higher coverages, we show that this 2D ordered phase coexists with the bulk phase. These results confirm the outstanding stability of the water monolayer adsorbed on MgO(001) found by recent molecular dynamics calculations.