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Boron chalcogenides under extreme conditions

Abstract : This thesis deals with the study of the boron chalcogenides under extreme conditions. After a short review of boron and boron compounds under extreme conditions (Chapter I), the experimental part (Chapter II) provides a brief description of the high-pressure devices used in this PhD work. The employed analytical techniques are described as well as the main principles of the performed ab initio theoretical calculations. The following part is devoted to our experimental and theoretical studies of β-B2O3 and r-BS. Chapter III presents the results of in situ high pressure XRD and phonon measurements (Raman and IR) of β-B2O3 at room temperature. The experimental data were considered and completed with results of ab initio calculations. Based on the total obtained dataset the complete description of β-B2O3 structure change and phonon behavior under compression at room temperature are detailled. Chapter IV contains the results of in situ high pressure XRD and vibrational spectroscopy studies on r-BS at room temperature. In combination with results of theoretical calculations the structure and phonon nature of r-BS in a wide pressure range at ambient temperature are described. Also, the formation of a new metastable high-pressure phase of BS is described and its probable structure and EoS are discussed. The last part (Chapter V) concerns the primary in situ XRD HP-HT studies in B-Se system. Based on the results of XRD and Raman measurements of the recovered samples, a new compound was synthesized. This compound was found to be metastable at ambient conditions. Its probable chemical composition and structure are discussed.
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  • HAL Id : tel-01660119, version 1


Kirill Cherednichenko. Boron chalcogenides under extreme conditions. Chemical Physics [physics.chem-ph]. Université Pierre et Marie Curie - Paris VI, 2015. English. ⟨NNT : 2015PA066602⟩. ⟨tel-01660119⟩



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