Diamond and cubic boron nitride under high pressure: Raman scattering, equation of state and high pressure scale

Abstract

The development of the diamond-anvil cell has stimulated Raman-scattering investigation of vibrational modes in covalent crystals. The linear pressure coefficient reported for diamond by Hanfland et at' (2.90 ± 0.05 cm-¹/GPa) agrees to within mutual experimental error with the result of Boppard et aL² (2.87±0.01 cm-¹/GPa). As to cubic boron nitride, the only work by Sanjurjo ef aL3 reports 3.45 ± 0.07 cm-¹/GPa for LO- and 3.39 ± 0.08 cm-¹/GPa for TO- modes. Since no compressibility data are availablel¹⁻³, the mode Griineisen parameter γ = ‐ δ In γ/δ is defined as y = K/Y·dv/aP and depends on the bulk modulus K and the calibration of the ruby scale. The above papers report y= 0.96 and y=0.95±O.O3fordiamondand γ_Lo=1.21,γTo=1.51 forBN.