# An all-electron product-basis set: application to plasmon anisotropy in simple metals

## TL;DR

This paper introduces an efficient all-electron product-basis set for wave functions, enabling detailed analysis of plasmon anisotropy in simple metals, and demonstrates its accuracy and application in understanding dielectric responses.

## Contribution

It presents a novel basis set for wave function products, implemented in the LAPW method, facilitating accurate analysis of plasmon anisotropy in simple metals.

## Key findings

- The basis set accurately captures dielectric responses.
- Anisotropy in plasmon dispersion is linked to excitation spectra structures.
- Experimental observations of anisotropy are explained.

## Abstract

An efficient basis set for products of all-electron wave functions is proposed, which comprises plane waves defined over the entire unit cell and orbitals confined to small non-overlapping spheres. The size of the set and the basis functions are, in principle, independent of the computational parameters of the band structure method. The approach is implemented in the extended LAPW method, and its properties and accuracy are discussed. The method is applied to analyze the dielectric response of the simple metals Al, Na, Li, K, Rb, and Cs with a focus on the origin of the anisotropy of the plasmon dispersion in Al and Na. The anisotropy is traced to tiny structures of the one-particle excitation spectra of Al and Na, and relevant experimental observations are explained.