High-pressure synthesis, crystal structure, and properties of GdS₂ with thermodynamic investigations in the phase diagram Gd-S

Gadolinium disulfide was prepared by high-pressure synthesis at 8 GPa and 1173 K. It crystallizes in the monoclinic space group P12₁/a1 (No. 14) with lattice parameters a = 7.879(1) Aa; b = 3.936(1) Aa, c = 7.926(1) Aa and β = 90.08(1) . The crystal structure is a twofold superstructure of the aristotype ZrSSi and consists of puckered cationic [GdS]⁺ double slabs that are sandwiched by planar sulfur sheets containing S₂^2- dumbbells. The thermal decomposition of GdS₂ proceeds via the sulfur-deficient polysulfides GdS_1.9, GdS_1.85 and GdS_1.77 and eventually results in the sesquisulfide Gd₂S₃. GdS₂ is a paramagnetic semiconductor which orders antiferromagnetically at T_N = 7.7(1) K. A metamagnetic transition is observed in the magnetically ordered state. (Abstract Copyright [2010], Wiley Periodicals, Inc.)