Orthorhombic sphere packings. I. Invariant and univariant lattice complexes

Molecular crystals with a sole bearing contact: structural classes and statistical data

All the structural classes (SCs) of molecular crystals, which are possible to be formed by a sole intermolecular bearing contact, are derived from 1,1- and 2,1-transitive nets. There are 160 (167 including enantiomorphic pairs) monosystemic SCs (in which the molecules occupy one crystallographic orbit) and 244 (248) bisystemic SCs (in which the molecules occupy two crystallographic orbits), i.e. 404 (411) SCs in all. These are the only SCs which can correspond to a homodesmic crystal structure, either organic, or inorganic, in which the structural units are bonded in a single way. Statistical investigation of the Cambridge Structural Database (CSD) shows that ∼1% of monosystemic molecular crystals can be formed by a sole intermolecular bearing contact.

Isotopy classification of three-dimensional embedded nets

The article by Power et al. [Acta Cryst. (2020), A76 , 275–301 ] on the isotopy classification of crystal nets is discussed.

Monoclinic sphere packings. I. Invariant, univariant and bivariant lattice complexes

All homogeneous sphere packings were derived that refer to the two invariant, the four univariant and the three bivariant lattice complexes belonging to the monoclinic crystal system. In total, sphere packings of 29 types have been found. Only for five types is the maximal inherent symmetry of their sphere packings monoclinic whereas the inherent symmetry is orthorhombic for nine types, tetragonal for five types, hexagonal for six types and cubic for four types.