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@ARTICLE{Mittal:9354,
      author       = {Mittal, R. and Heid, R. and Bosak, A. and Forrest, T.R. and
                      Chaplot, S.L. and Lamago, D. and Reznik, D. and Bohnen, K.P.
                      and Su, Y. and Kumar, C. M. N. and Dhar, S.K. and
                      Thamizhavel, A. and Rueegg, Ch. and Krisch, M. and McMorrow,
                      D.F. and Brückel, T. and Pintschovius, L.},
      title        = {{P}ressure dependence of phonon modes across the tetragonal
                      to collapsed tetragonal phase transition in {C}a{F}e2{A}s2},
      journal      = {Physical review / B},
      volume       = {81},
      number       = {14},
      issn         = {1098-0121},
      address      = {College Park, Md.},
      publisher    = {APS},
      reportid     = {PreJuSER-9354},
      pages        = {144502},
      year         = {2010},
      note         = {Record converted from VDB: 12.11.2012},
      abstract     = {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.},
      keywords     = {J (WoSType)},
      cin          = {IFF-4 / IFF-5 / Jülich Centre for Neutron Science JCNS
                      (JCNS) ; JCNS / JARA-FIT},
      ddc          = {530},
      cid          = {I:(DE-Juel1)VDB784 / I:(DE-Juel1)VDB785 /
                      I:(DE-Juel1)JCNS-20121112 / $I:(DE-82)080009_20140620$},
      pnm          = {BioSoft: Makromolekulare Systeme und biologische
                      Informationsverarbeitung / Großgeräte für die Forschung
                      mit Photonen, Neutronen und Ionen (PNI)},
      pid          = {G:(DE-Juel1)FUEK505 / G:(DE-Juel1)FUEK415},
      shelfmark    = {Physics, Condensed Matter},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000277210200098},
      doi          = {10.1103/PhysRevB.81.144502},
      url          = {https://juser.fz-juelich.de/record/9354},
}