Crystal-structure properties and the molecular nature of hydrostatically compressed realgar
- Author(s)
- Clivia Hejny, Raffaela Sagl, Daniel M. Többens, Ronald Miletich-Pawliczek, Manfred Wildner, Lutz Nasdala, Angela Ullrich, Tonci Balic-Zunic
- Abstract
The structure of realgar, As4S4, and its evolution with pressure have been investigated employing in situ X-ray diffraction, optical absorption and vibrational spectroscopy on single-crystal samples in diamond-anvil cells. Compression under true hydrostatic conditions up to 5.40 GPa reveals equation-of-state parameters of V 0 = 799.4(2.4) �3 and K 0 = 10.5(0.4) GPa with = 8.7. The remarkably high compressibility can be attributed to a denser packing of the As4S4 mols. with shortening of the intermol. bonds of up to 12 %, while the As4S4 mols. remain intact showing rigid-unit behavior. From ambient pressure to 4.5 GPa, Raman spectra exhibit a strong blue shift of the Raman bands of the lattice-phonon regime of 24 cm-1, whereas frequencies from intramol. As-S stretching modes show negligible or no shifts at all. On pressurisation, realgar shows a continuous and reversible color change from bright orange over deep red to black. Optical absorption spectroscopy shows a shift of the absorption edge from 2.30 to 1.81 eV up to 4.5 GPa, and DFT calcns. show a corresponding redn. in the band gap. Synchrotron-based measurements on polycryst. samples up to 45.5 GPa are indexed according to the monoclinic structure of realgar.
- Organisation(s)
- Department of Mineralogy and Crystallography
- External organisation(s)
- Leopold-Franzens-Universität Innsbruck, voestalpine AG, Helmholtz-Zentrum Berlin für Materialien und Energie, Karlsruher Institut für Technologie, University of Copenhagen
- Journal
- Physics and Chemistry of Minerals
- Volume
- 39
- Pages
- 399-412
- No. of pages
- 14
- ISSN
- 0342-1791
- DOI
- https://doi.org/10.1007/s00269-012-0495-y
- Publication date
- 2012
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 105113 Crystallography, 105116 Mineralogy
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/6ca987d0-0f9a-4897-a611-1b5b3c28b4fa