Effects of spin structures on phonons in BaFe2As2

The dependences of phonons on the spin structures of BaFe2As2 were studied using first-principles supercell approach. We considered the nonmagnetic, checkerboard, stripe, and spin-density-wave structures as well as a spin structure labeled as STR17. We find that STR17 is lower in energy than the stripe. It is seen the similar to 20 meV missing peak at the generalized phonon density-of-states and the measured specific heat are well reproduced when the magnetic effects are accounted. We see phonon energy gaps for all the four magnetic structures but not for the nonmagnetic structure. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3464166]