On deformability of atoms---comparative study between atoms and atomic nuclei

TL;DR

This paper investigates whether atoms exhibit deformation similar to atomic nuclei by analyzing electron density distributions using various many-body computational methods, revealing that only open-shell atoms show valence-driven deformation.

Contribution

The study compares atomic and nuclear deformation, demonstrating that atomic electron densities deform mainly due to valence orbitals, unlike nuclei which deform collectively.

Findings

Open-shell atoms have deformed electron densities due to valence orbitals.

Core electron densities remain spherical in open-shell atoms.

Atomic nuclei can deform collectively, unlike atoms.

Abstract

Atomic nuclei can be spontaneously deformed into non-spherical shapes as many-nucleon systems. We discuss to what extent a similar deformation takes place in many-electron systems. To this end, we employ several many-body methods, such as the unrestricted Hartree-Fock method, post-Hartree-Fock methods, and the density functional theory, to compute the electron density distribution in atoms. We show that the electron density distribution of open-shell atoms is deformed due solely to the single-particle valence orbitals, while the core part remains spherical. This is in contrast to atomic nuclei, which can be deformed collectively. We qualitatively discuss the origin for this apparent difference between atoms and nuclei by estimating the energy change due to deformation. We find that nature of the interaction plays an essential role for the collective deformation.