Structural phase transition in deuterated benzil C{sub 14}D{sub 10}O{sub 2}: Neutron inelastic scattering

Journal Article · Sat Apr 01 00:00:00 EST 2006 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PHYSREVB.73.1· OSTI ID:20788042

Goossens, D J; Welberry, T R; Hagen, M E; Fernandez-Baca, J A ^[1]

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1. Research School of Chemistry, Australian National University, Canberra 0200 (Australia)

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 {gamma}-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 {gamma}-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 {gamma}-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 {gamma}-point optic mode. This behavior is inconsistent with the view that the {gamma}-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.

• OSTI ID: 20788042
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Vol. 73, Issue 13; Other Information: DOI: 10.1103/PhysRevB.73.134116; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BRAGG CURVE
BRILLOUIN ZONES
CARBON OXIDES
DEUTERIUM COMPOUNDS
DISPERSION RELATIONS
ENERGY SPECTRA
INELASTIC SCATTERING
INSTABILITY
MONOCLINIC LATTICES
NEUTRON DIFFRACTION
NEUTRONS
ORGANIC COMPOUNDS
PHASE TRANSFORMATIONS
PHONONS
SOLIDS
TRIGONAL LATTICES