Formation of PbCl2-type AHF (A = Ca, Sr, Ba) with partial anion order at high pressure. Issue 24 (25th May 2021)

• Record Type: Journal Article
• Authors: Tsuchiya, Yumi; Wei, Zefeng; Broux, Thibault; Tassel, Cédric; Ubukata, Hiroki; Kitagawa, Yuuki; Ueda, Jumpei; Tanabe, Setsuhisa; Kageyama, Hiroshi
• Is Part Of: Dalton transactions. Volume 50:Issue 24(2021)
• Page Start: 8385
• Page End: 8391
• Publication Date: 2021-05-25
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/d1dt01054a
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : PbCl2 -type AHF (A = Ca, Sr, Ba) with partial anion order is obtained by pressurization of fluorite-type AHF whose anions are fully disordered. Abstract : The high-pressure structures of alkaline earth metal hydride-fluorides (AHFs) (A = Ca, Sr, Ba) were investigated up to 8 GPa. While AHF adopts the fluorite-type structure ( Fm 3̄ m ) at ambient pressure without anion ordering, the PbCl2 -type (cotunnite-type) structure ( Pnma ) is formed by pressurization, with a declining trend of critical pressure as the ionic radius of the A 2+ cation increases. In contrast to PbCl2 -type LaHO and LaOF whose anions are fully ordered, the H − /F − anions in the high-pressure polymorph of SrHF and BaHF are partially ordered, with a preferential occupation of H − at the square-pyramidal site ( vs. tetrahedral site). First-principles calculations partially support the preferential anion occupation and suggest occupation switching at higher pressure. These results provide a strategy for controlling the anion ordering and local structure in mixed-anion compounds.