Abstract
${\mathrm{Ti}}_{50}{\mathrm{Pd}}_{50\ensuremath{-}x}{\mathrm{Cr}}_{x}$ is a high-temperature shape-memory alloy with a martensitic transformation temperature strongly dependent on the Cr composition. Prior to the transformation, a premartensitic phase is present with an incommensurate modulated cubic lattice with wave vector of ${q}_{0}=(0.22,0.22,0)$. The temperature dependence of the diffuse scattering in the cubic phase is measured as a function temperature for $x=6.5$, 8.5, and $10\phantom{\rule{0.3em}{0ex}}\mathrm{at.}\phantom{\rule{0.2em}{0ex}}%$. The lattice dynamics has been studied and reveals anomalous temperature and $q$ dependences of the $[110]\text{\ensuremath{-}}{\mathrm{TA}}_{2}$ transverse phonon branch. The phonon linewidth is broad over the entire Brillouin zone and increases with decreasing temperature, contrary to the behavior expected for anharmonicity. No anomaly is observed at ${q}_{0}$. The results are compared with first principles calculation of the phonon structure.
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