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A Neutron Scattering Study of Phonons in Per‐Deuterated S‐Triazine
Author(s) -
Dove M. T.,
Heilmann I. U.,
Kjems J. K.,
Kurittu J.,
Pawley G. S.
Publication year - 1983
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/pssb.2221200119
Subject(s) - inelastic neutron scattering , phonon , soft modes , deuterium , condensed matter physics , neutron scattering , materials science , inelastic scattering , phase transition , neutron , single crystal , scattering , molecular physics , atomic physics , optics , nuclear magnetic resonance , physics , nuclear physics , optoelectronics , dielectric , ferroelectricity
The lattice dynamics of a fully‐deuterated single crystal of s‐triazine is investigated using the technique of coherent inelastic neutron scattering. Detailed measurements of the temperature dependence of the dispersion of the soft acoustic mode associated with the ferroelastic phase transition are reported and compared with the qualitative behaviour of other acoustic modes. The results are in agreement with an analysis of the acoustic dynamical matrix for this material which predicts that in the high‐temperature phase the combination of elastic constants C 2 eff = 1/2( C 11 − C 12 ) C 44 − C 2 14 should become unstable on cooling towards the transition temperature. This effective elastic constant is found to have a temperature dependence of the form C eff = C 0 ( T − T 0 ) with C 0 = 3.404 × 10 6 Nm −2 K −1 and T 0 = 172.4 K. Measurements of some optic mode frequencies are also reported.