X-ray diffraction measurements and Raman spectroscopy at room temperature documented the equation of state and the frequency shifts for Eg, T2g and A1g vibrational modes of polycrystalline material under pressure (table 2). The data exhibited smooth pressure dependences, yielding a zero-pressure isothermal bulk modulus of 164±2GPa, in good accord with independent ultrasonic measurements, and revealed no evidence of structural or electronic phase transitions up to at least 25GPa.

High-Pressure Raman and X-Ray Diffraction Studies on LaB6. Godwal, B.K., Petruska, E.A., Speziale, S., Yan, J., Clark, S.M., Kruger, M.B., Jeanloz, R.: Physical Review B, 2009, 80[17], 172104

Table 2

Properties of Raman Modes of LaB6

ω: frequency (P=0), ∂ω/ωP: pressure dependence, γ: Grüneisen parameter