Pressure-induced change in the long-period stacking sequence of the close-packed layers in Mg₃In

Samples of the alloy Mg₃In were annealed at 200-250°C in the Bridgman-anvil-type press under pressures between 20 and 100 kbar. After being quenched to ambient pressure and temperature, the crystal structure was studied by X-ray diffraction. The number of close-packed layers in one repeating unit of the alloy structure is twelve with the stacking sequence (3)₃ when annealed under the atmospheric pressure, but at 20, 35 and 55 kbar it increases to eighteen with the sequence (31)₃, and at 75 and 100 kbar a 24-layered structure with the sequence (311)₃ has been found to form. The pressure-induced change in the layer-stacking sequence in Mg₃In is similar to the change with the decrease in the electron-atom ratio previously observed for the ternary alloys Mg₃(In_1-x,Cd_x).