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Lattice Dynamics of Fe 0.65 Ni 0.35 Classical Invar
Author(s) -
Maliszewski E.,
Bednarski S.
Publication year - 1999
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/(sici)1521-3951(199902)211:2<621::aid-pssb621>3.0.co;2-5
Subject(s) - invar , phonon , softening , condensed matter physics , inelastic neutron scattering , transverse plane , lattice (music) , inelastic scattering , physics , lattice constant , materials science , scattering , thermodynamics , thermal expansion , quantum mechanics , diffraction , structural engineering , acoustics , engineering
The lattice dynamics of the invar Fe 0.65 Ni 0.35 single crystal was investigated at room temperature. The phonon dispersion relations along the [100], [110], and [111] directions are measured by inelastic neutron scattering. The Born‐von Karman analysis, using the seven‐neighbour model, is carried out and the force constants and elastic constants are calculated. The phonon frequency shifts Δω( q ) and the self‐energy Σ j ( q , ω j ( q )) functions are determined for Fe 0.65 Ni 0.35 from the experimental phonon frequencies for the alloy and Ni crystals. The dips observed on these functions made it possible to disclose the same phonon softening on longitudinal L [100] branch as is on transverse T 1 [110] branch. The softening of the longitudinal branches disclosed by these functions has been observed for the first time in these investigations. The rich and coherent structure of these functions seems to contain a lot of essential information on interatomic coupling and will enable testing of various models proposed to explain the invar effect.