Comment on "Theory of electron energy loss in a random system of spheres"

TL;DR

This paper critiques a recent theory on electron energy loss in random sphere systems, highlighting its neglect of magnetic effects, incorrect low-k limit, and improper screened potential, questioning its validity.

Contribution

It provides a critical analysis pointing out fundamental flaws in Barrera and Fuchs's theoretical approach to electron energy loss.

Findings

Neglects magnetic excitations and retardation effects.

Fails to produce correct Maxwell-Garnett limit at low wavevector.

Uses an incorrect screened potential at all wavevectors.

Abstract

In a recent paper, Barrera and Fuchs [Phys. Rev. B 52, 3256 (1995)] provide a theory of electron energy loss in a random system of spheres. In this comment, we point out that the approach of Barrera and Fuchs (A) completely ignores magnetic excitations and retardation, which is inconsistent with the data of energy loss of fast electrons, (B) does not yield the correct k-->0 limit, hence, does not recover correctly the Maxwell-Garnett formula, and (C) does not use the correct screened potential at any k.