Can we talk about ionic bonds in molecules? Yes, just as we do for covalent bonds.

A claim that ionic bonds exist only in ionic solids is critically analyzed by focusing on the controversial LiH molecule, classified as covalent by non-orthogonal valence bond supporters, polar-covalent by molecular orbital advocates, and ionic by real-space proponents. Using orbital invariant techniques we show that LiH can be regarded ionic in the same manner that dihydrogen is considered covalent.

Role of the Radical Character in Singlet Fission: An Ab Initio and Quantum Chemical Topology Analysis.

The radical character of molecules exhibiting singlet fission is related to the energy level matching relationships that facilitate this process. Using a linear H model molecule, we employ quantum chemical topology descriptors based on full configuration interaction calculations to rationalize singlet fission. In this context, the influence of the closed-shell to diradical and diradical to tetraradical character on the singlet fission energy matching conditions is analyzed.

A Dynamical Density Field That Shows the Localizability of Electrons: The Exchange-Correlation Ehrenfest Force.

A gradual but steady tide in theoretical chemistry is favoring the exploration of atomic and molecular interactions through the dynamical forces perceived and exerted by the particles of a system. By integrating the quantum mechanical force operator over all the spin and all but one of the spatial coordinates of the electrons, the Ehrenfest force density field reveals these forces directly and is separable into a classical term, related to the electric field, and a quantum mechanical correction, which we introduce and analyze for various atoms and molecules in this work. This exchange-correlation Ehrenfest force density field, (), excludes the dominant nuclear components that shape the full Ehrenfest field, revealing information about electron sharing, pairing, and delocalization.