Incommensurate phase transition of αPbO at 208 K

Abstract The structure of the alpha phase of the lead monoxide at room temperature is well known and very simple. It consists of layers of alternate regular square pyramids PbO4 in a tetragonal lattice (P4/nmm; aT = bT = 3.9704 A; cT = 5.022 A; Z = 2). The apex of each pyramid is occupied by the electronic lone pair of the Pb2+ ions (Galy, Meunier, Andersson and Astrom, 1975).