AnSn Coordination Polyhedra (An = Th, U, Np, Pu, Am, Cm, or Cf) in Crystal Structures

Voronoi-Dirichlet polyhedra (VPD) were used to perform a crystal-chemical analysis of 216 sulfides containing in their crystal structures 296 coordination polyhedra AnS(n) (An = Th, U, Np, Pu, Am, Cm or Cf). It was found that, in sulfides, there occur An(II), An(III), An(IV), U(V), and U(VI) atoms that bind 6 to 10 sulfur atoms existing as S2- or S- ions. The most important parameters of the VD polyhedra were characterized, dependence was revealed of how the multiplicity of the S--S- bond depends on its length. It was shown that, in contrast to the procedure based on an analysis of the lengths of the An-S bonds, makes it possible to reliably determine the valence state of An atoms in the sulfide structures.