Cation vacancy order in the K0.8+xFe1.6-ySe2 system: five-fold cell expansion accommodates 20% tetrahedral vacancies

Abstract

Ordering of the tetrahedral site vacancies in two crystals of refined compositions K0.93(1)Fe1.52(1)Se2 and K0.862(3)Fe1.563(4)Se2 produces a fivefold expansion of the parent ThCr2Si2 unit cell in the ab plane which can accommodate 20% vacancies on a single site within the square FeSe layer. The iron charge state is maintained close to +2 by coupling of the level of alkali metal and iron vacancies, producing a potential doping mechanism which can operate at both average and local structure levels.

5 pages 3 figures accepted for publication in Chemical Science Chem. Sci., DOI:10.1039/C1SC00070E

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Cited by in corpus (3)

• Intrinsic phase separation in superconducting K0.8Fe1.6Se2 (Tc= 31.8 K) single crystals
• Ternary iron selenide K${}_{0.8}$Fe${}_{1.6}$Se${}_2$ is an antiferromagnetic semiconductor
• Pressure cycle of superconducting Cs0.8Fe2Se2: a transport study