Journal
JOURNAL OF PHYSICAL CHEMISTRY C
Volume 118, Issue 40, Pages 23189-23201Publisher
AMER CHEMICAL SOC
DOI: 10.1021/jp507826j
Keywords
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Funding
- Spanish Consolider Ingenio 2010 Program [CSD2007-00045]
- Brazilian Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) [201050/2012-9]
- Spanish MICINN [MAT2010-21270-004-01/03/04, MAT2013-46649-C4-2/3/4-P]
- Spanish MINECO [CTQ2012-36253-C03-02]
- Vicerrectorado de Investigacion de la Universitat Politecnica de Valencia [UPV2011-0914 PAID-05-11, UPV2011-0966 PAID-06-11]
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We report a joint experimental and theoretical study of the structural and vibrational properties of synthetic sphaerobismoite (beta-Bi2O3) at high pressures in which room-temperature angle-dispersive X-ray diffraction (XRD) and Raman scattering measurements have been complemented with ab initio total energy and lattice dynamics calculations. Striking changes in Raman spectra were observed around 2 GPa, whereas X-ray diffraction measurements evidence no change in the tetragonal symmetry of the compound up to 20 GPa; however, a significant change exists in the compressibility when increasing pressure above 2 GPa. These features have been understood by means of theoretical calculations, which show that beta-Bi2O3 undergoes a pressure-induced isostructural phase transition near 2 GPa. In the new isostructural beta' phase, the Bi3+ and O2- environments become more regular than those in the original beta phase because of the strong decrease in the activity of the lone electron pair of Bi above 2 GPa. Raman measurements and theoretical calculations provide evidence of the second-order nature of the pressure-induced isostructural transition. Above 20 GPa, XRD measurements suggest a partial amorphization of the sample despite Raman measurements still show weak peaks, probably related to a new unknown phase which remains up to 27 GPa. On pressure release, XRD patterns and Raman spectra below 2 GPa correspond to elemental Bi-I, thus evidencing a pressure-induced decomposition of the sample during downstroke.
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