Phase Transition of CuS1-xSex (0 < x < 1) Studied by Powder X-Ray Diffractometry

Determination of the Local Crystal-Chemical Features of Complex Chalcogenides by Copper, Antimony, and Arsenic NQR

“…Upon cooling this interaction can stimulate the phase transition. Such scenario is supported by the dependence of the T PT value on the Se amount in mixed samples CuS 1-x Se x (0≤x≤1) (Nozaki et al, 1995). Actually, since the Cu(1)-Cu(2) bonds in CuS are longer than that in CuS 1-x Se x , this phase transition in CuS occurs at lower T. Thus, NQR spectra signify that -CuSe material is related crystal-chemically to CuS and have a somewhat similar layered structure, but either of Cu(1)Se 3 and Cu(2)Se 4 complexes in this compound are strongly distorted and this aspect leads again to layered A 1 -B-A 2 structure, as in CuS, but with different and uncertain structures of layers A 1 , A 2 , and B (Fig.…”

“…Their comparative analysis can also introduce new information concerning their electronic structure as well as highlight some reasons for low-temperature phase transitions in these materials (Section II.1). In general, the copper selenide CuSe undergoes two phase transitions upon cooling: from -CuSe into -CuSe modification near 398 K and to -CuSe at 323 K (Nozaki et al, 1995;Milman, 2002). It was proposed that -CuSe has the same structure as CuS (Berry, 1954) and thetransformation of CuSe is similar to that in CuS at T PT =55 K (Nozaki et al, 1995).…”

“…In general, the copper selenide CuSe undergoes two phase transitions upon cooling: from -CuSe into -CuSe modification near 398 K and to -CuSe at 323 K (Nozaki et al, 1995;Milman, 2002). It was proposed that -CuSe has the same structure as CuS (Berry, 1954) and thetransformation of CuSe is similar to that in CuS at T PT =55 K (Nozaki et al, 1995). Notably, Raman spectroscopy and powder X-ray diffratometry shows that in the system of CuS 1-x Se x (0≤x≤1) compounds T PT increases from 55 K for x=0 up to 398 K for x=1 (Nozaki et al, 1995).…”

“…It was proposed that -CuSe has the same structure as CuS (Berry, 1954) and thetransformation of CuSe is similar to that in CuS at T PT =55 K (Nozaki et al, 1995). Notably, Raman spectroscopy and powder X-ray diffratometry shows that in the system of CuS 1-x Se x (0≤x≤1) compounds T PT increases from 55 K for x=0 up to 398 K for x=1 (Nozaki et al, 1995). However, it was found that -CuSe is characterized by 13 lines in the spectrum with NQR frequencies in the range of 13-2 MHz at 4.2 K. First, this aspect points strongly to the presence of strong deformations of the -CuSe crystal and gives evidence that CuS andCuSe are not isostructural as it was supposed earlier (Berry, 1954).…”

“…However, such a substitution mechanism implies basically the p r e s e r v a t i o n o f l a y e r e d s t r u c t u r a l m o t i v e i n C u S 1-x Se x (as in CuS). The preferential occupation of Se at the S(2) sites (Nozaki et al, 1995) leads to the approaching of some Se(2) atoms to Cu(1) sites and to the formation of distorted tetrahedrons Cu(1)Se(1) 3 Se(2) 1 inCuSe instead of triangular units Cu(1)S(1) 3 in CuS (Fig. 1).…”