Item

Abstract

The effect of high pressures, up 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 similar to11% 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 nonstoichiometry, are proposed as
an explanation for the unusually large variation of the
pressure dependence of T-c for different samples of MgB2.