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Electronic structure describes the quantum states and spatial distribution of a system's electrons, including their energies, occupancies and correlations. It determines much of the chemical bonds, optical response and reactivity of atoms, molecules and solids.

An electron configuration is one compact approximate description, but it is not the full many-electron state. In molecular calculations, molecular orbitals and electron density reveal where charge is distributed; a many-electron wave function also encodes correlations. In a crystal, energy bands express how allowed electronic energies depend on wavevector. Approximations such as Hartree-Fock theory and density functional theory address different representations of the same underlying quantum problem.

John E. McGrady studies how electronic structure controls the chemical bonds and magnetism of inorganic metal clusters. In an endohedral metal cluster, a metal atom sits inside a cage; calculating the interaction between that atom and the cage can distinguish a nearly independent enclosed metal from a structure with strongly shared electron density. His group uses density functional theory and multiconfigurational methods to examine these possibilities.^[ref]

Homepage: mcgrady.chem.ox.ac.uk/

A metal-halide perovskite is a crystalline material in which a halide-based framework adopts the perovskite structure or a related arrangement. In the common $AB{X}_3$ description, $B$ is a metal cation, $X$ a halide and $A$ a larger charge-balancing cation, which can be inorganic or molecular.

Connectivity and distortion of the metal–halide framework influence electronic structure and optical absorption. This makes the family important in solar cells and light-emitting devices. The structural name alone does not specify one composition, stability or band gap; substitutions, dimensionality and defects can change those properties.

A metal nitrosyl complex contains a coordinated nitric-oxide group, conventionally written M–NO. The metal–nitrogen–oxygen arrangement may be approximately linear or bent, and changes in geometry correlate with different bonding and reactivity.

Assigning every nitrosyl a single fixed formal charge can obscure the delocalized electronic structure. A useful counting approach groups the metal and nitrosyl together and counts the relevant electrons of that fragment. Geometry, spectroscopy and electron count then constrain one another. The original 1974 treatment explicitly relates these structural alternatives to chemical reactions.^[ref]