PHONON MODES AND VIBRATIONAL ENTROPY OF MIXING IN FE-CR

Results from neutron inelastic-scattering experiments on Fe, Cr, and t hree bcc Fe-Cr alloys were analyzed with a Born-von Karmin model to ob tain phonon density-of-states (DOS) curves. We compared the phonon DOS of the bce Fe-Cr alloys to the composite phonon DOS from appropriate fractions of the phonon DOS of the pure metals Fe and Cr. In the high- temperature limit, we obtained the vibrational entropy of mixing of Fe and Cr to be 0.141, 0.201, and 0.214 k(B)/atom for alloys of Fe70Cr30 , Fe53Cr47, and Fe30Cr70, respectively, with the disordered solid solu tion having the larger vibrational entropy. Some expected effects of v ibrational entropy on the chemical unmixing transformation in Fe-Cr ar e discussed.