Formation of PbCl₂-type AHF (A = Ca, Sr, Ba) with partial anion order at high pressure

Abstract

The high-pressure structures of alkaline earth metal hydride-fluorides AHF (A = Ca, Sr, Ba) were investigated up to 8 GPa. While AHF adopts the fluorite-type structure (Fm-3m) at ambient pressure...

Trihalide Mixing by Size-Flexible H– Ions in Layered Ba2H3 (Cl, Br, I)

“…20 The anion order−disorder transition in a series of LnHO (Ln = La−Er) is also interpreted by the H − size softness. 21 This hydride characteristic plays an important role in the structure of nonoxide hydrides, such as the structural phase transition in AHF (A = Ca, Sr, Ba) 22 and the cubic stability of M 3 HCh (M = Li and Na; Ch = S, Se, and Te). 23 Given these structural features and excellent ionic conduction, Ba 2−δ H 3−2δ X is an ideal platform to study the "indirect" effect of the chemical disorder of halide ions on hydride conductivity.…”

“…The anion order–disorder transition in a series of LnHO (Ln = La–Er) is also interpreted by the H – size softness . This hydride characteristic plays an important role in the structure of nonoxide hydrides, such as the structural phase transition in AHF (A = Ca, Sr, Ba) and the cubic stability of M 3 HCh (M = Li and Na; Ch = S, Se, and Te) …”

Pressure-Induced Anion Order–Disorder Transition in Layered Perovskite Sr2LiHOCl2

“…69,70 Among the three-anion-disordered compounds, Sr 2 LiHOBr 2 has the largest bottleneck for H − ion diffusion (Figure S6 and Table S3), which gives better H − ion conductivity. In addition, since the Ba-for-Sr and Br-for-Cl replacements corresponds to the application of a negative chemical pressure, 67,68…”

“…The same trend was seen in A 2 CuO 2 X 2 ( A = Ba, Sr; X = Cl, Br). , Among the three-anion-disordered compounds, Sr 2 LiHOBr 2 has the largest bottleneck for H – ion diffusion (Figure S6 and Table S3), which gives better H – ion conductivity. In addition, since the Ba-for-Sr and Br-for-Cl replacements corresponds to the application of a negative chemical pressure, , it is interesting to compare the effect of the chemical pressure on the order–disorder transition. Unfortunately, however, no comparison could be made because the 2-GPa synthesis formed only impurity phases (e.g., SrHBr and Sr 4 OBr 6 and hypothetical Ba 2 LiH 3 Cl 2 ) and there is no trace of the target phases.…”