Phonon-phason coupling in icosahedral quasicrystals

From relaxation simulations of decoration-based quasicrystal structure models using microscopically based interatomic pair potentials, we have calculated the (usually neglected) phonon-phason coupling constant. Its sign is opposite for the two alloys studied, i-AlMn and i-(Al,Cu)Li; a dimensionless measure of its magnitude relative to the phonon and phason elastic constants is of order 1/10, suggesting its effects are small but detectable. We also give a criterion for when phonon-phason effects are noticeable in diffuse tails of Bragg peaks.Comment: 7 pages, LaTeX, uses Europhys Lett macros (included

Critical thickness for InAs quantum dot formation on (3 1 1)B InP substrates

We report on the critical thickness for InAs quantum dot (QD) formation on (3 1 1)B InP substrates. Firstly, critical thicknesses for InAs QD formation on InP surfaces have been measured by reflection high-energy electron diffraction. Large change of th

Phason softening in the AlPdMn icosahedral phase

The diffuse scattering located close to Bragg reflections has been studied as a function of the temperature on a single grain of the AlPdMn icosahedral phase. Between $600^\circ$C and $800^\circ$C there is a reversible and continuous transition. When the temperature increases, the diffuse scattering diminishes whereas high-$Q_\bot$ reflections have their intensity increased. All results are well interpreted within the elasticity theory of quasi-crystals: the changes in diffuse scattering shape and intensity when lowering the temperature are due to a softening of the K1 phason elastic constant. The time decay of these long-wavelength phason fluctuations is larger than 5 ns