The function of interstices in cubic unit cells

Abstract The occurrence of interstices, their number and position in cubic crystal structures is investigated from three viewpoints: physical metallurgy, crystallography and quantum-mechanical computations. Interstices are anything but free space left over. They play an important role in the stability or alteration of crystal structures, because they are able to include electronic charge density. Together with structural and thermal vacancies they are a universal means of reacting to the influencing control of those physical factors that govern the formation of the concrete structure. The description of the positions of interstices in a crystal structure can be accomplished in the simplest case by viewing the unit cell, by computing the Wigner–Seitz cells of the atoms in the unit cell or by computing the electronic charge density distribution. However, the latter two are very expensive. The interaction of the Fermi surface ('necks', from Pippard's experiment) with the {111} planes of the first Brillouin zone of copper and the non-occurrence of a structure alteration in this case is interpreted as a direct consequence of the charge-containing ability of the interstices. Acknowledgements The author gratefully acknowledges many valuable remarks from Professor P. Paufler (Institute of Structure Physics, University of Technology, Dresden) concerning the crystallographic aspects. The author also thanks Dr. U. Nitzsche for support with the FPLO program package and Dr. M. Richter for many discussions concerning quantum-mechanical calculations (Leibniz-Institute of Solid State and Materials Research, Dresden). Thanks also to T. Hutsch for carrying out the computation of the charge density distributions. Notes Email: ruhnow@rcs.urz.tu-dresden.de Additional informationNotes on contributorsM. Ruhnow Footnote* Email: ruhnow@rcs.urz.tu-dresden.de