High pressure polymorphism of LiBH4 and of NaBH4. Issue 41 (21st July 2021)

• Record Type: Journal Article
• Authors: Marizy, Adrien; Geneste, Grégory; Garbarino, Gaston; Loubeyre, Paul
• Is Part Of: RSC advances. Volume 11:Issue 41(2021)
• Page Start: 25274
• Page End: 25283
• Publication Date: 2021-07-21
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/d1ra00816a
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : Diamond anvil cell experiments are used along with density functional theory calculations to extend the phase diagram of LiBH4 & NaBH4 and explore new NaBH4 (H2 ) x compounds at Mbar pressures. Abstract : The pressure-induced structural changes in LiBH4 and in NaBH4 have been investigated experimentally up to 290 GPa by coupling Raman spectroscopy, infrared absorption spectroscopy and synchrotron X-ray diffraction. This data set is also analysed in the light of Density Functional Theory calculations performed up to 600 GPa. The [BH4 ] − unit appears to be remarkably resistant under pressure. NaBH4 remains stable in the known Pnma γ-phase up to 200 GPa and calculations predict a transition to a metallic polymeric C 2/ c phase at about 480 GPa. LiBH4 is confirmed to exhibit a richer polymorphism. A new Pnma orthorhombic phase VI is found to be stable above 60 GPa and there are hints of a possible phase VII above 160 GPa. DFT calculations predict that two other high pressure LiBH4 phases should appear at about 290 and 428 GPa. A very slight solubility of H2 inside phases II, III and V of LiBH4 is observed. A NaBH4 (H2 )0.5 complex is predicted to be stable above 150 GPa.