Nonlinear effects in light-ion stopping powers within real-time time-dependent density functional theory

TL;DR

This paper uses real-time TDDFT calculations to reveal that nonlinear effects significantly influence light-ion stopping powers in warm dense matter, challenging traditional linear-response assumptions and guiding future model improvements.

Contribution

The study demonstrates the importance of nonlinear effects in ion stopping powers using TDDFT, providing insights beyond linear models and informing future model development.

Findings

Nonlinear effects modify stopping powers by about 10% near the Bragg peak.

Partial neutralization models capture some qualitative aspects but lack quantitative accuracy.

Effective charge can exceed the bare ion charge, indicating complex nonlinear contributions.

Abstract

Electronic stopping power models describing fuel heating processes in inertial fusion energy concepts typically assume linear-response behavior through quadratic scaling with the projectile charge. We report the results of real-time time-dependent density functional theory (TDDFT) calculations indicating that even for low-Z ions, nonlinear processes modify stopping powers in warm dense matter by about 10% near and below the Bragg peak. By describing partial neutralization of slow ions, analytic effective charge models capture some qualitative aspects of the TDDFT results but do not always offer quantitative accuracy. Cases where the effective charge inferred from TDDFT exceeds the bare ion charge suggest that more complex nonlinear effects also contribute. These findings will inform future improvements to more efficient stopping power models.