High pressure phase transition in metallic LaB6: Raman and X-ray diffraction studies

Abstract

High pressure Raman and angle dispersive X-ray diffraction (ADXRD) measurements on the metallic hexaboride LaB 6 have been carried out upto the pressures of about 20 GPa. The subtle phase transition around 10 GPa indicated in Raman measurements is confirmed by ADXRD experiments to be a structural change from cubic to orthorhombic phase. Ab-initio electronic band structure calculations using full potential linear augmented plane wave method carried out as a function of pressure show that this transition is driven by the interception of Fermi level by electronic band minimum around the transition pressure.

Buffer-layer-enhanced growth of a single-domain LaB6 (1 0 0) epitaxial thin film on a MgO (1 0 0) substrate via pulsed laser deposition

“…The three expected main peaks were observed at 711 (T 2g ), 1158 (E g ), and 1289 (A 1g ) cm À 1 , which is in agreement with intramolecular vibrations of the B 6 molecule [34]. The observed peak positions were slightly larger than the previously reported value for single crystal bulk LaB 6 [35]; that is caused by internal stress and/or an expanding lattice parameter in the film system [34,35]. This phenomenon agreed well with the XRD results.…”

Evidence for a subtle structural symmetry breaking in EuB6

“…These modes correspond to internal displacement of B atoms in the B 6 octahedron [21]. Previous RS works [21][22][23][24][25][26][27][28][29] have reported these modes at ∼780 (T 2g ), ∼1150 (E g ), and ∼1260 (A 1g ) cm −1 . Besides these phonons, additional modes at ∼200 and ∼1400 cm −1 were also reported.…”

First-Principles Study of the Nonlinear Elasticity of Rare-Earth Hexaborides REB6 (RE = La, Ce)

“…Besides, high-pressure phase transitions in LaB 6 and CeB 6 have been investigated experimentally. By using Raman and X-ray diffraction measurements on LaB 6 , Teredesai et al [10] proposed that a phase transition from cubic to orthorhombic crystal structure occurs around 10 GPa, while Godwal et al [11] stated that there is no structural phase transitions up to at least 25 GPa. By using X-ray diffraction measurements on CeB 6 , Leger et al [12] revealed no structural phase transition at ambient temperature up to 20 GPa.…”