Fragility and Boson peak formation in a supercooled liquid

e analyze results for the Boson peak from the neutron time of flight spectr oscopy data on Ge-As-Se, and Raman spectra data on m-TCP and OTP, using a r ecent mode coupling model that takes into account the coupling of density f luctuations with vibrational modes in presence of defects in the supercoole d state. From the experimental results for different materials we observe t hat for more fragile systems characterized by increasing fragility paramete r m, a slower relaxation of the defect-density correlation is needed to giv e rise to the observed peak in the spectra. (C) 2001 Published by Elsevier Science B.V.