High-pressure structural behaviour of Cu0.5Fe0.5Cr2S4: An experimental and theoretical study

Highlights: •First high-pressure study of the thiospinel Cu½Fe½Cr2S4. •First determination of the bulk modulus and its pressure derivative. •Phase transition, reducing symmetry to lower than cubic, at 14.5 GPa. •Jahn–Teller activity of Cu(2+) and high-spin to low-spin transition of Fe(2+). -- Abstract: The structural behaviour of Cu0.5Fe0.5Cr2S4 has been studied experimentally and theoretically at pressures up to 44 GPa. The experiments are supported by density functional calculations using the full-potential linear muffin-tin orbital method for investigating ground state properties and high-pressure behaviour. We report here the first experimental and theoretical determinations of the bulk modulus: B0 = 106(2) GPa and B0′ = 4.0 (experimental), and B0 = 96 GPa and B0′ = 3.9 (calculated). Moreover, a pressure-induced structural and electronic phase transformation occurs at 14.5 GPa accompanied by a volume collapse of about 6%. Tentatively, the high-pressure phase is assigned the defect NiAs structure of Cr3S4 type with space group I2/m (12). The mechanism of the phase transition is explained by a Jahn–Teller type distortion, associated with geometrical frustration and magnetic spin changes