Premonitory effects in Cu3Au near the order-disorder transformation

P. Bardhan, Haydn Chen, J. B. Cohen

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Just above the order—disorder critical temperature (Tc) in Cu3Au several unusual effects have been reported: (1) The ratio of diffuse intensity at the 003 position to that at the 001 decreases markedly. (2) There is a sudden increase in the total diffuse X-ray scattering due to mean-square displacements. (3) Phonon groups broaden. (4) Optical modes appear. Additional details of these effects are described here. Also it is shown that: (5) there are no significant changes in the phonon dispersion curves; and (6) there is a marked increase in (quasi-static) anharmonic interactions (which were observed in the X-ray diffraction pattern). All of these unusual effects are interpreted as arising from long-lived fluctuations above Tc, like the low temperature ordered phase. The results suggest these fluctuations contain a high density of thick antiphase boundary.

Original languageEnglish
Pages (from-to)1653-1666
Number of pages14
JournalPhilosophical Magazine
Issue number6
StatePublished - 1 Jan 1977


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