Unusual pressure response of the E2g mode and elastic shear modulus C44 in hcp scandium

Scandium (Sc) was studied by Raman spectroscopy to pressures up to 20GPa. The E-2g mode frequency increases throughout the stability field of the hexagonal-close-packed (hcp) phase, which contrasts the softening of this mode observed in its heavier homologue Y and the related regular lanthanides. The unusually low mode Gruneisen parameter and the small increase of elastic modulus C-44 are discussed with respect to pressure-induced changes of the electronic structure.