Trajectory sampling and finite-size effects in first-principles stopping power calculations

Alina Kononov, Thomas W. Hentschel, Stephanie B. Hansen & Andrew D. Baczewski 

npj Computational Materials 9: 205 (2023); Published online: 30 October 2023

编辑概述：电子阻止本领计算：定量轨迹评估与优化

高性能计算已彻底改变了材料科学，使预测、设计和对材料性能的理解成为可能，并补充和加速实验工作。对激光和粒子辐照等刺激的动态非线性响应进行模拟是对计算要求最高的材料模拟类型之一，需要对包含数百个原子和数千个电子的扩展系统进行实时演化模拟。在极端条件下，高温会导致材料中部分占据的电子轨道数量增加一个数量级，这要么需要额外的近似，要么进一步将计算资源需求增加到数百万CPU小时或更多。在这种情况下，有意识的设计模拟方法对于在保持可接受的计算成本的同时最大化计算效果是至关重要的。针对此，一种创新的预采样方法于近期被提出，该方法采用精心选择的几个短轨迹的平均结果。在本文中，来自美国Sandia国家实验室的Alina Kononov等人，针对这种采样提出了一种补充的方法，使用一个定量度量来指导先验选择一个单一的、具有代表性的弹道轨迹，用于电子阻止本领的第一性原理计算。作者以铝中的质子停止为例，证明了这种方法即使在晶体材料中也具有实用价值：研究发现，实现计算与经验数据的一致需要一个高质量的轨迹，尽管人们普遍假设随机选择就足够了。本文所提出的方法有助于系统控制和分析第一性原理电子阻止本领计算中的两个重要的近似：弹道轨迹和选择有限超胞。这些策略不仅将提高TDDFT电子阻止本领计算的准确性和效率，而且随着量子计算机可行性的提高，也将证明它们对更高级别的理论和量子模拟算法的价值。

Editorial Summary: Electronic stopping power calculations: Quantitative metric for evaluating and optimizing trajectories

High-performance computing has revolutionized materials science, enabling prediction, design, and unprecedented understanding of materials properties to complement and accelerate experimental efforts. Modeling dynamic, nonlinear responses to stimuli such as laser and particle irradiation falls among the most computationally demanding types of materials simulations, requiring real-time evolution of extended systems containing hundreds of atoms and thousands of quantum-mechanical electrons. For materials in extreme conditions, high temperatures result in orders-of-magnitude increases in the number of partially occupied electronic orbitals, either requiring additional approximations or further escalating computational resource requirements to millions of CPU hours or more per calculation. In this context, deliberate design of simulations is crucial for maximizing insight while maintaining feasible computational costs. Recently, an innovative pre-sampling approach that averages results from several short trajectories carefully selected was proposed. In this work, Alina Kononov et al. from the Sandia National Laboratories, USA, presented a complementary method that uses a quantitative metric to guide a priori selection of a single, representative projectile trajectory for first-principles calculations of electronic stopping power. Using proton stopping in aluminum as an exemplar, the authors demonstrated the utility of such an approach even in a crystalline material, as the authors found that achieving agreement with empirical data requires a high-quality trajectory despite widespread presumptions that a random choice suffices. The combination of approaches in this work facilitates systematic control and analysis of two important approximations in first-principles stopping power calculations: the choice of projectile trajectory and finite supercells. These strategies will not only enhance the accuracy and efficiency of TDDFT stopping power calculations, but also prove valuable for higher levels of theory and quantum simulation algorithms on quantum computers as their viabilities improve.