• journal_title：The Canadian Mineralogist
• Contributor：Benedetta Periotto ; Tonci Balić-žunić ; Fabrizio Nestola
• Publisher：Mineralogical Association of Canada
• Date：2012-
• Format：text/html
• Language：en
• Identifier：10.3749/canmin.50.2.201
• journal_abbrev：Can Mineral
• issn：0008-4476
• volume：50
• issue：2
• firstpage：201
• section：Articles

A single crystal of natural berthierite, FeSb₂S₄, was investigated at high pressure by means of X-ray diffraction using a diamond-anvil cell equipped with diamond backing plates. No phase transitions were indicated up to 8 GPa. The third-order Birch–Murnaghan equation of state, calculated using high-accuracy volume–pressure data up to 8.05 GPa, gave the following coefficients: V₀ = 608.78(7) ų, K_T0 = 37.2(2) GPa and K′ = 7.0(1). The evolution of the structure as a function of pressure has been determined at seven different pressures up to 7.41 GPa. As in other structures with stereochemically active lone-electron pairs (LEP), the Sb³⁺ LEP, influencing long Sb–S bonds in berthierite, accommodate most of the compression. The Fe octahedron, which is the stiffest coordination polyhedron in berthierite, increases its distortion until approximately 5 GPa, but shows pronounced stiffening at higher pressures. This deformation at high pressures can be related to an increase in the Jahn–Teller effect on the Fe²⁺ coordination. The influence of Fe on compressional behavior makes a distinct difference between the compression of berthierite and that of stibnite, Sb₂S₃. The bridging Fe coordination between the structural rods in berthierite makes it stiffer. This, together with the direct structural relation to the analogous PbBi₂S₄, galenobismutite, makes the compressional characteristics of berthierite more akin to those of galenobismutite, despite quantitative differences in the stereochemical expression of the LEP of Sb³⁺ and Bi³⁺.