Related Experiment Video
Updated: Sep 6, 2026

Construction and Systematical Symmetric Studies of a Series of Supramolecular Clusters with Binary or Ternary Ammonium Triphenylacetates
Published on: February 15, 2016
Are crystal structures getting better? A temporal and elemental analysis of the Cambridge Structural Database
1Faculty for Chemistry and Pharmacy, University of Regensburg, Universitätsstrasse 31, Regensburg, 93053, Germany.
Abstract:
In this article, the temporal progression of quality indicators in the Cambridge Structural Database is evaluated statistically as a simplistic and accessible measure for structural quality trends. R1 showed a strong decrease until 1980 followed by comparatively small changes, whereas wR2 increased significantly between 2000 and 2025. Residual electron-density extrema remained broadly stable, although the magnitude of the residual densities showed a small significant decrease. Exploratory normalization by unit-cell volume produced decreasing recent R1 and wR2 ratios, whereas F(000)-normalized R1 decreased and F(000)-normalized wR2 remained stable. Also, quality indicators are plotted on an elemental basis, and their trends are described.
More Related Videos
Related Concept Videos
Determination of Crystal Structures
Crystal Density
Structures of Solids
Crystal Field Theory - Tetrahedral and Square Planar Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
Ionic Crystal Structures
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...

