In which type of crystal structure are octahedral holes formed?

In crystal structures, octahedral holes are formed due to the arrangement of atoms in coordinated positions that allow for voids created by the packing of atoms. In a body-centered cubic structure, the octahedral holes are located at the center of the cube and at the edges, while in a face-centered cubic structure, they are found at the center of the cube and in the faces. Similarly, hexagonal close-packed structures also have octahedral holes that are formed between two triangular planes of atoms.

The presence of octahedral holes is fundamental in understanding how these different crystal lattices can host ions or smaller atoms, leading to various compounds and materials. The geometry and packing efficiency of these structures lead to an effective utilization of the available space, allowing for octahedral holes to be present.

Thus, since octahedral holes are inherent features of the body-centered cubic, face-centered cubic, and hexagonal close-packed structures, it is correct to state that octahedral holes can be found in all of these types of crystal structures.