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Crystal structure and lattice dynamics of AlB2 under pressure and implications for MgB2

I. Loa·K. Kunc·K. Syassen·P. Bouvier
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Abstract

The effect of high pressures to 40 GPa on the crystal structure and lattice dynamics of AlB2 was studied by synchrotron x-ray powder diffraction, Raman spectroscopy, and first-principles calculations. There are no indications for a pressure-induced structural phase transition. The Raman spectra of the metallic sample exhibit a well-defined peak near 980 cm^{-1} at 0 GPa which can be attributed to the Raman-active E_{2g} zone-center phonon. Al deficiency of ~11% in AlB2, as indicated by the x-ray data, changes qualitatively the electronic structure, and there are indications that it may have a sizable effect on the pressure dependence of the E_{2g} phonon frequency. Similar changes of the pressure dependence of phonon frequencies, caused by non-stoichiometry, are proposed as an explanation for the unusually large variation of the pressure dependence of T_c for different samples of MgB2.

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I. Loa, K. Kunc, K. Syassen, P. Bouvier. 2002-06-05. Crystal structure and lattice dynamics of AlB2 under pressure and implications for MgB2. https://doi.org/10.1103/physrevb.66.134101

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