TY  - JOUR
AU  - Mittal, R.
AU  - Heid, R.
AU  - Bosak, A.
AU  - Forrest, T.R.
AU  - Chaplot, S.L.
AU  - Lamago, D.
AU  - Reznik, D.
AU  - Bohnen, K.P.
AU  - Su, Y.
AU  - Kumar, C. M. N.
AU  - Dhar, S.K.
AU  - Thamizhavel, A.
AU  - Rueegg, Ch.
AU  - Krisch, M.
AU  - McMorrow, D.F.
AU  - Brückel, T.
AU  - Pintschovius, L.
TI  - Pressure dependence of phonon modes across the tetragonal to collapsed tetragonal phase transition in CaFe2As2
JO  - Physical review / B
VL  - 81
IS  - 14
SN  - 1098-0121
CY  - College Park, Md.
PB  - APS
M1  - PreJuSER-9354
SP  - 144502
PY  - 2010
N1  - Record converted from VDB: 12.11.2012
AB  - The pressure dependence of a large number of phonon modes in CaFe2As2 with energies covering the full range of the phonon spectrum has been studied using inelastic x-ray and neutron scatterings. The pressure range was large enough to cover the first-order phase transition into the so-called collapsed phase where the c-axis contracts by about 6% whereas a and b axes expand by about 1.5%. Our main result is that pressure-induced phonon frequency shifts are well explained by the changes in relevant bond lengths throughout the pressure range, including those associated with the first-order phase transition. Specifically, the frequencies of phonons polarized in the ab plane as well as the Fe-As bond lengths change little across the phase transition. On the other hand, the transverse-acoustic phonons propagating along the c direction stiffen very significantly in response to the large contraction of the bonds along the c axis. Nonmagnetic density-functional calculations describe the frequencies in both the zero pressure and in the collapsed phase in a satisfactory way if based on the respective experimental crystal structures. This suggests that there is no need to invoke changes in magnetic moments on Fe atoms to explain the pressure-induced frequency shifts.
KW  - J (WoSType)
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000277210200098
DO  - DOI:10.1103/PhysRevB.81.144502
UR  - https://juser.fz-juelich.de/record/9354
ER  -