A single crystal X-ray and HRTEM study of new series of compounds DyCux (x=4.5, 4 and 3.5)

A series of monoclinic compounds DyCux (x = 4.5,4 and 3.5) is described. It is constructed from structural blocks AB(5) (cubic AuBe5 structure type) and AB(2) (cubic MgCu2 structure type) by stacking nAB(5) + AB(2) and giving the compositions A(2)B(7), AB(4), A(4)B(17), A(5)B(22), A(6)B(27),... , AB(5). The resulting monoclinic superstructures can be derived from the cubic AuBe5 type by introducing planar defects parallel to {hhh} that lead to a nearly orthogonal approximate to (n + 2) x (n + 2) x (n + 2 - 0.5) supereells. The present series is analogous to the monoclinic-hexagonal-trigonal-orthorhombic series A(n+1)B(5n+2) obtained by the stacking (n-1)AB(5) + A(2)B(7) where AB(5) is of the hexagonal CaCu5 structure type and A(2)B(7) is of the monoclinic Zr2Ni7 structure type. (C) 2003 Elsevier Science (USA). All rights reserved.