Structure of the tenfold $d$-Al-Ni-Co quasicrystal surface

The structure of the tenfold surface of decagonal Al-Ni-Co was studied using low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). The surface region is a relaxed truncated bulk structure, having the same composition as the bulk. The outermost layer spacing is contracted by 10% relative to the bulk interlayer spacing, while the next layer spacing is expanded by 5%. A small degree of intralayer rumpling was observed within each layer. There is a one-to-one correspondence between protrusions observed in the STM images and a subset of atoms in the model structure, indicating that in-plane reconstruction is minimal.