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Title: The Structural Phase Transition in Deuterated Benzil, C 14D 10O 2

Abstract

Neutron inelastic scattering has been used to examine the structural phase transition in deuterated benzil C{sub 14}D{sub 10}O{sub 2}. The transition in benzil, in which the unit cell goes from a trigonal P3{sub 1}21 unit cell above T{sub c} to a cell doubled P2{sub 1} unit cell below T{sub c}, leads to the emergence of a Bragg peak at the M-point of the high temperature Brillouin zone. It has previously been suggested that the softening of a transverse optic phonon at the {lambda}-point leads to the triggering of an instability at the M-point causing the transition to occur. This suggestion has been investigated by measuring the phonon spectrum at the M-point for a range of temperatures above T{sub c} and the phonon dispersion relation along the {lambda}-M direction just above T{sub c}. It is found that the transverse acoustic phonon at the M-point is of lower energy than the {lambda}-point optic mode and has a softening with temperature as T approaches T{sub c} from above that is much faster than that of the {lambda}-point optic mode. This behavior is inconsistent with the view that the {lambda}-point mode is responsible for triggering the phase transition. Rather the structural phase transition inmore » benzil appears to be driven by a conventional soft TA mode at the M-point.« less

Authors:
 [1];  [1];  [2];  [2]
  1. Australian National University, Canberra, Australia
  2. ORNL
Publication Date:
Research Org.:
High Flux Isotope Reactor; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
978163
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review B; Journal Volume: 73; Journal Issue: 13
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ACOUSTICS; BRAGG CURVE; BRILLOUIN ZONES; DISPERSION RELATIONS; INELASTIC SCATTERING; INSTABILITY; NEUTRONS; OPTICS; PHONONS

Citation Formats

Goosens, D. J., Welberry, T. R., Hagen, Mark E, and Fernandez-Baca, Jaime A. The Structural Phase Transition in Deuterated Benzil, C14D10O2. United States: N. p., 2006. Web. doi:10.1103/PhysRevB.73.134116.
Goosens, D. J., Welberry, T. R., Hagen, Mark E, & Fernandez-Baca, Jaime A. The Structural Phase Transition in Deuterated Benzil, C14D10O2. United States. doi:10.1103/PhysRevB.73.134116.
Goosens, D. J., Welberry, T. R., Hagen, Mark E, and Fernandez-Baca, Jaime A. Sun . "The Structural Phase Transition in Deuterated Benzil, C14D10O2". United States. doi:10.1103/PhysRevB.73.134116.
@article{osti_978163,
title = {The Structural Phase Transition in Deuterated Benzil, C14D10O2},
author = {Goosens, D. J. and Welberry, T. R. and Hagen, Mark E and Fernandez-Baca, Jaime A},
abstractNote = {Neutron inelastic scattering has been used to examine the structural phase transition in deuterated benzil C{sub 14}D{sub 10}O{sub 2}. The transition in benzil, in which the unit cell goes from a trigonal P3{sub 1}21 unit cell above T{sub c} to a cell doubled P2{sub 1} unit cell below T{sub c}, leads to the emergence of a Bragg peak at the M-point of the high temperature Brillouin zone. It has previously been suggested that the softening of a transverse optic phonon at the {lambda}-point leads to the triggering of an instability at the M-point causing the transition to occur. This suggestion has been investigated by measuring the phonon spectrum at the M-point for a range of temperatures above T{sub c} and the phonon dispersion relation along the {lambda}-M direction just above T{sub c}. It is found that the transverse acoustic phonon at the M-point is of lower energy than the {lambda}-point optic mode and has a softening with temperature as T approaches T{sub c} from above that is much faster than that of the {lambda}-point optic mode. This behavior is inconsistent with the view that the {lambda}-point mode is responsible for triggering the phase transition. Rather the structural phase transition in benzil appears to be driven by a conventional soft TA mode at the M-point.},
doi = {10.1103/PhysRevB.73.134116},
journal = {Physical Review B},
number = 13,
volume = 73,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}