The interplay between experiment and theory in charge-density analysis

The comparison of theory and experiment in charge-density analysis remains a cornerstone of the field. Various levels of comparison are discussed, including static and dynamic electron densities, topological properties, d-orbital occupancies, electrostatic moments and intermolecular interactions, as well as the structure-factor restraint introduced in quantum-mechanical energy minimization by Jayatilaka and co-workers.

On the role of data quality in experimental charge-density studies

Electron distributions from multipolar refinement of two sets of high-resolution X-ray diffraction data of different quality, measured at T = 19 K from two different spherical crystals of the same compound, are analysed and compared.

The charge density of urea from synchrotron diffraction data

The charge density of urea is studied with a multipole model using very high precision synchrotron-radiation diffraction data.

Synchrotron charge-density studies in materials chemistry: 16 K X-ray charge density of a new magnetic metal-organic framework material, [Mn₂(C₈H₄O₄)₂(C₃H₇NO)₂]

A new magnetic metal-organic framework material, [Mn₂(C₈O₄H₄)₂(C₃H₇ON)₂], has been synthesized. The magnetic susceptibility and heat capacity has been measured from 2 to 400 K, and the electron density has been determined from 16 (1) K single-crystal synchrotron X-ray diffraction data.

High-resolution synchrotron data collection for charge-density work at 100 and 20 K

The bright synchrotron radiation at a short wavelength of ∼0.5 Å combined with low temperatures and modern CCD area detection provides outstanding experimental conditions for charge-density determinations. Synchrotron-based studies on several compounds are summarized, for example atomic properties of a highly substituted C₆₀ fullerene with about 100 atoms are reported.

Electron densities in relation to magnetism: γ-ray diffraction from transition-metal monoxides and difluorides

High-quality γ-ray structure factors are used to explore the electronic charge distribution in prototypic antiferromagnets.

Extinction-free electron diffraction refinement of bonding in SrTiO₃

A charge-density study of SrTiO₃ by extinction-free electron diffraction.

Shadowing and absorption corrections of high-pressure powder diffraction data: toward accurate electron-density determinations

The shadowing of the primary and reflection beams in high-pressure powder diffraction experiments using a diamond-anvil cell is analysed and a method for correcting reflection intensities is described. These corrections considerably improve the accuracy of the data, essential for electron-density determinations.

On functions and qu­antities derived from the experimental electron density

Electronic and exchange energy densities, a local temperature and local entropy as well as a local Fermi momentum and one-electron potential calculated from the experimentally derived electron density and its derivatives using approximate functionals of the density functional theory are considered. Their application to studies of the electron structure of compounds with different types of chemical bonds is given.

The quantum topological electrostatic potential as a probe for functional group transferability

The electrostatic potential can be used as an appropriate and convenient indicator of how transferable an atom or functional group is between two molecules. Quantum-chemical topology is used to define the electron density of a molecular fragment and the electrostatic potential it generates.

Topological properties of the electron density of solids and molecules. Recent developments in Oviedo

Some of the latest advances in the analysis of electron density are reviewed, including topological indices that provide a useful characterization of the global properties of the density, specific results on some prototypical metal and low heteropolarity systems and calculation of the local curvature of the interatomic surface.

The local form of the source function as a fingerprint of strong and weak intra- and intermolecular interactions

The local form of the source function for the electron density at a given point is introduced and analysed for the second-row diatomic hydrides and a number of prototypical hydrogen-bonded systems. Differences in the local source contributions to the density at bond critical points due to chemical bonding (deformation density) and crystallization (interaction density) are also explored and are found to be more informative and experimentally detectable than are the corresponding changes for the bond-critical-point properties of intermolecular interactions.

The metal–insulator phase transition in mixed potassium–rubidium electro-sodalites

The collapse under pressure of the antiferromagnetic ground state of the potassium–rubidium electro-sodalite is studied. The linearized augmented plane wave with local orbitals basis set is described and the special considerations needed for setting it up for systems such as the electro-sodalites are discussed.

Electron-density studies of molecular magnetic materials

Electron-density studies of molecular magnetic materials are reviewed.

Studies of electric field induced structural and electron-density modifications by X-ray diffraction

The results obtained by diffraction from crystals under electric fields are reviewed and are illustrated by examples for a number of different compounds.

`In-situ' charge-density studies of photoinduced phenomena: possibilities for the future?

The experimental considerations required to obtain photoinduced crystal structures is described and related to the experimental and theoretical requirements of charge-density studies. The viability of combining these two experimental methodologies to realize a photoinduced charge-density study is explored.

The experimental electron density in polymorphs A and B of the anti-ulcer drug famotidine

A multipole description of the electron-density distribution in the two polymorphs of famotidine is given. The electrostatic potential shown on the molecular surfaces provides additional information on molecular reactivity.

Topological analyses and bond characterization of 1,3,5,7-tetra-tert-butyl-s-indacene: a weak C_sp³—H⋯H—C_sp²-type di­hydrogen interaction

A 12 π-electron delocalized system and C_sp³—H⋯H—C_sp² weak dihydrogen interactions of tetra-tert-butyl-s-indacene are confirmed through topological analyses of the total electron density.

An experimental (120 K) and theoretical electron-density study of KMnO₄ and KClO₄

The experimental electron density ρ(r) of the two isomorphic salts KMnO₄ and KClO₄ was determined by a multipole analysis of accurate X-ray diffraction data at 120 K. The quantum theory of atoms in molecules was applied and the bonds were characterized using the topological parameters at the bond critical points.

Variable-temperature X-ray crystallographic studies: a complementary tool for charge-density investigation of soft (organometallic) bonds

The behaviour of bridged metal–metal bonds at varying temperatures is studied.

Electronic structure of the nickel(II) complex of the Schiff base of (S)-N-(2-benzoylphenyl)-1-benzylprolinamide and glycine

Charge-density studies of an Ni^II complex of the Schiff base of (S)-N-(2-benzoylphenyl)-1-benzylprolinamide and glycine prove an interaction between the Ni²⁺(d_z²) orbital and benzyl π-electron density.