Phason elastic constants of the icosahedral Al-Pd-Mn phase derived from diffuse scattering measurements

The diffuse scattering in the diffraction pattern of the icosahedral Al-Pd- Mn quasicrystalline phase has been measured on an absolute scale by X-ray a nd neutron scattering on single-grain samples. Most of the diffuse scatteri ng can be interpreted in the framework of the elasticity theory of icosahed ral quasicrystals considering only phason fluctuations. At room temperature the absolute values of the K-1/k(B)T and K-2/k(B)T phason elastic constant s are of the order of 0.06 and 0.031 atom(-1). The amount of diffuse scatte ring intensity is insensitive to the sample annealing treatment.