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Uranium is the only element known so far to exhibit a charge-density wave (CDW) instability (alpha phase; orthorhombic Cmcm space group, Z=2, To=43 K).The structure below the transition is complex, consisting of small displacements of the atoms along all three of the orthorhombic axis. The main displacement is associated with a doubling of the a axis, and it has been known for many years that the transition may be regarded as one in which a soft phonon condenses at this point half way across the Brillouin zone. The theory of Yamada (1993) suggests that the only important component of the phonon wavevector is that along [100]. We report here high-resolution neutron scattering experiments at low temperature which show that the principal softening occurs at the exact CDW points in the Brillouin zone. This result is in dizagreement with the suggestions of Yamada but in better agreement with a new theoretical approach by Fast et al. (1998).

Additional information

Authors: MARMEGGI J C, CNRS Grenoble (FR);CURAT R, Institut Laue Langevin Grenoble (FR);BOUVET A, Institut Laue Langevin Grenoble (FR);LANDER G H, ITU Karlsruhe, Karlsruhe (DE)
Bibliographic Reference: Paper presented: International Conference on Phonons, Lancaster (GB), July 27th, 1998
Availability: Available from DG XIII as Paper EN 41931 ORA
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