Phonon dispersion of bcc iron to 10 GPa

The phonon dispersion of bcc iron under high pressure to 10 GPa was measure d at 300 K by inelastic neutron scattering. Its pressure dependence is surp risingly uniform. Contrary to the behavior found in other bcc elements, the re is a lack of any significant pretransitional behavior close to the marte nsitic bcc-hcp transition which could be related to the Burgers mechanism. This finding confirms predictions by spin-polarized total energy calculatio ns that explain the transition by the effect of pressure on the magnetism o f iron. The high pressure frequencies were used to develop a lattice dynami cal model from which thermodynamic quantities can be determined at any pres sure to 10 GPa.