arrangementelectron

Arrangementelectron is a hypothetical framework in theoretical chemistry and condensed matter physics that describes the dynamic rearrangement of electron density in response to external perturbations. The term blends “arrangement” and “electron” and is used to emphasize nonlocal, time-dependent reorganization of electrons beyond static orbital occupation.

In this framework, electron rearrangement is treated as a process that maps external stimuli to a trajectory of electron density and occupancy across a system. Predictive tools draw on quantum-chemical methods such as time-dependent density functional theory (TDDFT), multireference configuration interaction, and coupled-cluster theory, often combined with population analyses to identify regions of charge buildup and depletion.

A central construct is the arrangement descriptor, an abstract representation that encodes how electrons populate different fragments or spatial regions. This descriptor aims to capture both local rearrangements within molecular fragments and larger-scale charge-transfer processes, providing a way to quantify and compare electronic responses across systems.

Applications discussed in literature include excited-state dynamics, photocatalysis, and materials with strong electron-phonon coupling, where understanding electron movement is essential for predicting reactivity and transport properties. The concept also serves an educational role, helping researchers visualize how electrons reorganize under perturbations.

However, arrangementelectron is not an established standard and remains informal in most discussions. It faces criticism for potential redundancy with existing descriptors of electron density and orbital populations, and for lacking a unique, universally accepted formalism.

See also: electron density, orbital occupancy, TDDFT, charge transfer, electron correlation, rearrangement energy.