Inorganic structure prediction with GRINSP

A new computer program is described, GRINSP ( geometrically restrained inorganic structure prediction), which allows the exploration of the possibilities of occurrence of 3-, 4-, 5- and 6-connected three-dimensional networks. Hypothetical ( as well as known structure) models for binary compounds are produced with exclusive connection of polyhedra by corners, such as [MX3] triangles in M2X3 formulation, [MX4] tetrahedra in MX2 ( zeolites or dense SiO2 polymorphs), [MX5] polyhedra in M2X5, and finally [MX6] octahedra in MX3 polymorphs. Moreover, hypothetical ternary compounds are built up by combinations of either two different polyhedra or two different radii for two different cations adopting the same coordination. The cost function is based on the agreement of the model interatomic distances with ideal distances provided by the user. The Monte Carlo algorithm first finds structure candidates selected after the verification of the expected geometry, and then optimizes the cell parameters and the atomic coordinates. A satellite software ( GRINS) uses the predicted models and produces the characteristics of isostructural compounds which would be obtained by cationic substitutions. A huge list of CIF files of hypothetical boron oxide polymorphs ( including nanotubes), zeolites, aluminium and 3d-element fluorides, fluoroaluminates, borosilicates, titanosilicates, gallophosphates etc., is freely available at the PCOD ( Predicted Crystallography Open Database).