|About this Abstract
||2017 TMS Annual Meeting & Exhibition
||Computational Thermodynamics and Kinetics
||Effects of Magnetism on the Vibrational Entropy of Iron and Cementite
||Brent Fultz, Lisa Mauger, Jane Herriman, Olle Hellman, Matthew Lucas, Sally Tracy
|On-Site Speaker (Planned)
Phonon spectra of bcc iron and cementite (Fe<SUB>3</SUB>C) were independently measured from low temperatures through their Curie temperatures to assess the effects of magnetism on vibrational entropy. The phonon spectra of both iron and cementite underwent rapid changes near the Curie temperatures (1044 K and 460 K). The change in magnetic order altered the vibrational entropy of bcc iron by approximately 0.3 k<SUB>B</SUB>/atom, but the effect in cementite was an order-of-magnitude smaller. Phonon dispersions and densities of states were calculated by dft methods, and were also obtained by fitting the experimental data to a Born - von Karman model with interatomic forces used as fitting parameters. In bcc iron, the largest magnetic effects were on the low transverse acoustic branch, probably owing to changes in second-nearest-neighbor interatomic forces. In cementite, the dynamics of one of the Fe sites (FeII) was more sensitive to magnetism than the other.
||Planned: Supplemental Proceedings volume