The monoclinic lattice distortion of η′-Cu6Sn5

Crystal structure of incommensurate ηʺ-Cu1.235Sn intermetallic

“…Upon starting to do full-pattern based refinements on the basis of the PXRD data, it first succeeded to get convincing fits to the fundamental reflections using the average structure. Thereby, it turned out that, against original expectation from the evaluation of PXRD patterns of the η′ phase [16,17], visible reflection splitting occurred for some of the fundamental reflections (see Figure 4c). In terms of the monoclinic lattice parameters of the average structure, it turned out that the lattice angle β av deviated 1 In Ref.…”

“…In recent experimental works involving the present authors [16][17][18], some new insight has been obtained on differently ordered Cu 1+δ Sn phases making up of Cu 6 Sn 5 IMC:…”

“…In order to keep maximum agreement with the descriptions of the superstructures in [10], as also used in Ref. [16], the modulation vector is modified here. Both descriptions, of course, imply the same atomic structures.…”

“…In Ref. [16], it was shown how the symmetry breaking distortions of a superstructure can be expressed in terms of a symmetric strain tensor following the idea of the Aizu strain [31]. Such a strain tensor fulfills the symmetry restrictions of the crystal class of the analyzed crystal structure.…”

“…i. A method has been devised quantifying the characteristic monoclinic distortion present in the η′ superstructure in terms of a strain tensor calculated from the lattice parameters of the η′ phase [16].…”