Phonon spectrum and related thermodynamic properties of bcc-Fe with an edge dislocation

Abstract

The phonon spectrum and related thermodynamic properties of perfect bcc-Fe crystal and bcc-Fe with a [1 0 0] edge dislocation are calculated with the recursion method by using F-S N-body potential. For perfect bcc-Fe crystal, our calculated results of phonon spectrum, vibrational entropy, heat capacity and vibrational energy are in excellent agreement with the experiment and related calculation results. The configuration of [1 0 0] edge dislocation obtained by molecular dynamics relaxation shows that a string of interstices is formed along the dislocation line, thus the local vibrational densities of states (LDOS) of atoms in the dislocation core are quite different from the bulk phonon spectrum, and there exist some sharp peaks in certain frequencies. However, for the atoms away from the dislocation core, their LDOS's gradually approach the bulk spectrum. Meanwhile, the local vibrational energies of the dislocation core atoms are also evidently changed except for the atoms on the slip plane. These results indicate that the bondings between the atoms in dislocation core are greatly changed. Furthermore, it is also proved that the average vibrational entropy of bcc-Fe with a [1 0 0] edge dislocation is higher than that of perfect crystal.