# MgB\_2 under pressure: phonon calculations, Raman spectroscopy, and optical reflectance Source: [MgB\_2 under pressure: phonon calculations, Raman spectroscopy, and optical reflectance]() Collection index: [llms.txt]() Data updated: 2025-10-24T10:40:58.543Z Authors: K. Kunc, I. Loa, K. Syassen, R. K. Kremer, K. Ahn Published: 2001-05-21T14:43:45.000Z ## Abstract The effect of pressure on optical phonon frequencies of MgB$\_2$ has been calculated using the frozen-phonon approach based on a pseudopotential method. Gr\\"uneisen parameters of the harmonic mode frequencies are reported for the high-frequency zone-center $E\_{2g}$ and $B\_{1g}$ and the zone-boundary $E\_{2u}$ and $B\_{2u}$ modes at $A$. Anharmonic effects of phonon frequencies and the implications of the calculated phonon frequency shifts for the pressure dependence of the superconducting transition temperature of MgB$\_2$ are discussed. Also reported are Raman and optical reflectance spectra of MgB$\_2$ measured at high pressures. The experimental observations in combination with calculated results indicate that broad spectral features we observed in the Raman spectra at frequencies between 500 and 900 cm$^{-1}$ cannot be attributed to first-order scattering by zone-center modes, but originate in part from a chemical species other than MgB$\_2$ at the sample surface and in part from a maximum in the MgB$\_2$ phonon density of states. Low-temperature Raman spectra taken at ambient pressure showed increased scattering intensity in the region below 300 cm$^{-1}$. ## Recorded benchmark results A research result applies to its stated dataset, split, metric and evaluation configuration. Compare like-for-like settings, preserve the metric's unit and direction, and distinguish paper-reported results from independent reproduction. The best result recorded here is not a claim of exhaustive, current global coverage. ## Original sources and implementation [Original paper]() [PDF]()