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We report on high-pressure angle-dispersive X-ray diffraction data up to 15 GPa and ab initio total-energy calculations up to 242 GPa for KBrO3. No phase transition was found below 15 Pa in contrast to previously reported data. Its experimental bulk modulus in the quasi-hydrostatic regime is B0 = 18.8 (9) GPa with a bulk modulus pressure derivative B0 = 8.2 (4). However, according to our ab initio calculations, KBrO3 significantly reduces its rhombohedral distortion via small cooperative movements of the atoms and the structure progressively approaches the cubic symmetry, where the KBr subarray would adopt a topology similar to that of the corresponding B2-type bromide. This rearrangement of atoms is directly related to the Buerger's mechanism of the B1–B2 phase transition for halides, confirming that cations (second neighbors) do not arrange in an arbitrary way. The O atoms forming the [BrO3] pyramidal units move smoothly with pressure to the center of the [K8] cube faces, where electron localization function calculations present their maxima in other B2-type compounds, eventually adopting the perovskite-type structure at P ≃ 152 GPa. Our data on KBrO3 has been compared with chemically substituted isostructural halates, providing new insights on the compressibility of this family of compounds.

Supporting information


Crystallographic Information File (CIF)
Contains datablocks global, I


Rietveld powder data file (CIF format)
Contains datablock I


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Tables of experimental data from powder XRD and theoretically calculated lattice parameters and atomic coordinates at different pressures

CCDC reference: 1427985

Computing details top

Program(s) used to refine structure: FULLPROF.

(I) top
Crystal data top
KBrO3Z = 3
Mr = 167Mo Kα radiation
Trigonal, R3mT = 295 K
Hall symbol: R 3 -2"white
a = 6.0104 (17) Åcylinder, 0.5 × 0.5 mm
c = 8.162 (4) ÅSpecimen preparation: Prepared at 295 K and 101.3 kPa
V = 255.35 (15) Å3
Data collection top
Xcalibur Oxford Difraction
Data collection mode: transmission
Radiation source: sealed X-ray tube2θmin = 3.975°, 2θmax = 34.645°, 2θstep = 0.024°
Specimen mounting: 0.5-mm glass capillary
Refinement top
Rp = 12.697Profile function: pseudo-Voigt
Rwp = 93.27910 parameters
Rexp = 35.1120 restraints
RBragg = 11.630Background function: 68 background points
1282 data points
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
K0.000000.000000.000000.039 (19)*
Br0.000000.000000.483 (9)0.023 (10)*
O0.476 (8)0.524 (8)0.068 (11)0.03 (3)*

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