hide
Free keywords:
-
Abstract:
The layered compounds CuCr[P2Se6] (m.p. 730-degrees-C, incongruent),
AgCr[P2Se6] (m.p. 720-degrees-C, incongruent), AgAl[P2Se6] (m.p.
588-degrees-C, congruent), CuIn[P2Se6] (m.p. 642-degrees-C,
incongruent), AgIn[P2Se6] (m.p. 673-degrees-C, congruent),
alpha-AgGa[P2Se6] (m.p. 450-degrees-C, congruent) and beta-AgGa[P2Se6]
(metastable) were prepared from the elements in evacuated silica tubes
(molar ratios M(I):M(III):P:Se = 1:1:2:6) by heating up to 750-degrees-C
(10 h) followed by quenching/annealing or by cooling from the melt
(Bridgman technique).
The crystal structures of CuIn[P2Se6], AgIn[P2Se6] (trigonal, P31cBAR; a
= 639.2(0), 648.3(1); c = 1333.8(1), 1333.0(4) pm; Z = 2) and
beta-AgGa[P2Se6] (trigonal, P31cBAR; a = 637.5(6), c = 1332.0(1) pm; Z =
2) are related to the CdI2 structure type whereas the crystal structures
of CuCr[P2Se6], AgCr[P2Se6] and AgAl[P2Se6] (monoclinic, C2/m; a =
619.3(3), 630.5(8), 634.8(5); b = 1072.4(2), 1091.7(3), 1098.9(3); c =
690.9(9), 699.1(1), 702.8(4) pm; beta = 107.2(7), 107.7(1),
107.2(1)-degrees; Z = 2) are related to the CdCl2 structure type.
Alpha-AgGa[P2Se6] (orthorhombic, Pbca; a = 1216.9(5), b = 2248.4(6), c =
747.3(2) pm; Z = 4) shows close relationships to the crystal structure
of Ag4[P2Se6].
