Intrinsically localized vibrations and the mechanical properties of α-uranium

• Published in: Journal of alloys and compounds 2007-10, Vol.444, p.129-132
• Main Authors: Manley, M.E., Yethiraj, M., Sinn, H., Volz, H.M., Alatas, A., Lashley, J.C., Hults, W.L., Lander, G.H., Thoma, D.J., Smith, J.L.
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Deformation and plasticity (including yield, ductility, and superplasticity); Exact sciences and technology; Lattice dynamics; Localized modes; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Phonons and vibrations in crystal lattices; Physics
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2006.09.137

Recent experiments have indicated that the high-temperature properties of α-uranium may be strongly influenced by the formation of randomly distributed intrinsically localized vibrational modes, just a few atoms across in size. One observation was a loss of mechanical ductility that coincided with the formation of the intrinsically localized mode (ILM). Here, we consider this observation in more detail. In particular, we use the anisotropic thermal expansion behaviour to estimate the strains associated with each ILM and consider the implications for the forces between ILMs and the defects responsible for mechanical deformation. In the process we also suggest that an unusual transition from positive to negative thermal expansion along the [0 1 0] direction may be caused by the formation of ILMs.