Phonon–phason coupling in a Mg–Ga–Al–Zn icosahedral quasicrystal

Abstract

Precise X-ray diffraction measurements have revealed that phonon (conventional) strain is introduced at the phase transition from an icosahedral quasicrystal to its orthorhombic crystal approximant in a Mg–Ga–Al–Zn alloy. From the magnitude of the measured phonon strain, the phonon–phason coupling constant has been evaluated. This constant is approximately −0.03μ (μ: shear modulus) and it is in good agreement with the result of a theoretical calculation reported previously (W.-J. Zhu and C.L. Henley, Europhys. Lett. 46 748 (1999)). This is the first study that experimentally evaluates the phonon–phason coupling constant in any existing quasicrystalline phase.

Acknowledgements

We thank Professor C. L. Henley of Cornell University and Professor S. Takeuchi of the Science University of Tokyo for their valuable comments and discussion. This work was financially supported by Core Research in Environmental Science and Technology (CREST), Japan Science and Technology Corporation.