Electron-Ion Structure Factors and the General Accuracy of Linear Response

TL;DR

This paper demonstrates that electron-ion structure factors in fluid metals can be effectively described using linear response theory combined with hard-sphere models, revealing two main classes based on valence and explaining the success of linear response in metals.

Contribution

It introduces a classification of electron-ion structure factors in metals based on valence and explains the general applicability of linear response theory in these systems.

Findings

Electron-ion structure factors fall into two classes based on valence.

Linear response theory successfully describes most metallic systems.

Metallic hydrogen is an exception to the linear response applicability.

Abstract

We show that electron-ion structure factors in fluid metallic systems can be well understood from an application of linear response in the electron system, combined with hard-sphere like correlation for the ionic component. In particular, we predict that electron-ion structure factors fall into two general classes, one for high ($Z>3$) and one for low ($Z\leq2$) valence metals, and make suggestions for experiments to test these ideas. In addition, we show how the general success of electronic linear response for most metallic systems stems in part from an intrinsic interference between atomic and electronic length scales which weakens the nonlinear response. The main exception to this is metallic hydrogen.