Identification of the high-pressure phases of alpha-SnWO4 combining x-ray diffraction and crystal structure prediction

TL;DR

This study investigates the high-pressure phases of alpha-SnWO4 using X-ray diffraction and crystal structure prediction, revealing two phase transitions and proposing detailed structures for the high-pressure phases.

Contribution

The paper combines experimental X-ray diffraction with computational predictions to identify and characterize two high-pressure phases of alpha-SnWO4, providing new structural insights.

Findings

Identified two structural phase transitions at 12.9 GPa and 17.5 GPa.

Proposed crystal structures for the high-pressure phases.

Reported equations of state and elastic properties for all phases.

Abstract

We have characterized the high-pressure behavior of alpha-SnWO4. The compound has been studied up to 30 GPa using a diamond-anvil cell and synchrotron powder X-ray diffraction. We report evidence of two structural phase transitions in the pressure range covered in our study, and we propose a crystal structure for the two high-pressure phases. The first one, observed around 12.9 GPa, has been obtained combining indexation using DICVOL and density-functional theory calculations. The second high-pressure phase, observed around 17.5 GPa, has been determined by using the CALYPSO code, the prediction of which was supported by a Le Bail fit to the experimental X-ray diffraction patterns. The proposed structural sequence involves two successive collapses of the unit-cell volume and an increase in the coordination number of Sn and W atoms. The room-temperature equations of state, the principal axes of compression and their compressibility, the elastic constants, and the elastic moduli are reported for {\alpha}-SnWO4 and for the two high-pressure phases.