Atomic short-range order (SRO) relating to a phason is key to resolve phase stabilities in Al-Ni-Co decagonal quasicrystals. Complicated SRO was determined by anomalous X-ray scattering. At the same time, anisotropic distributions of diffuse scattering appeared around Bragg reflections. Moreover, the anomalous Debye-Waller factor was seen in an order-disorder phase transition at high temperature.
