Exploring energy landscapes of charge multipoles using constrained density functional theory

• DOI: 10.48550/arxiv.2305.13988
• Publication Date: 2023-01-01
• Authors: Luca Schaufelberger; Maximilian E. Merkel; Aria Mansouri Teh...; Nicola A. Spaldin; Claude Ederer
• Keywords: Maxima and minima; Charge density; Energy landscape

We present a method to constrain local charge multipoles within density-functional theory. Such quantify the anisotropy of distribution around atomic sites and can indicate potential hidden orders. Our allows selective control specific multipoles, facilitating quantitative exploration energetic landscape outside minima. Thus, it enables clear distinction between electronically structurally driven instabilities. demonstrate effectiveness this by applying quadrupoles in prototypical orbitally ordered material KCuF$_3$. intersite multipole-multipole interactions as well energy-lowering related formation an isolated quadrupole. also map out energy function size quadrupole moment its minimum, enabling quantification multipole fluctuations their equilibrium value. Finally, we study solid solution KCu$_{1-x}$Zn$_x$F$_3$ characterize behavior across tetragonal-to-cubic transition. provides powerful tool for studying symmetry breaking materials with coupled electronic structural instabilities potentially