npj: 重离子范围—时间依赖性密度泛函的预测

2019 年 4 月 23 日 知社学术圈

海归学者发起的公益学术平台

分享信息，整合资源

交流学术，偶尔风月

精确预测固体中高能离子范围分布的能力，对深入理解辐射效应具有重要意义，同时关乎诸多应用材料的改性，包括半导体加工、能源生产、医药，以及核技术的发展。虽然物质中离子阻挡已成为数十年来重要的科学研究焦点，但许多关键科学问题仍未得到解决。离子在穿过固体时速度减慢并沉积能量的过程在微观上是核阻挡和电子阻挡导致能量损失的过程，对其准确的预测就需要找到更为精确的模型来描述局部电子结构。钨（W）是目前聚变反应堆设计中面向等离子体元件的主要候选材料，所以了解W中辐射损伤的机制对于未来聚变发电厂的安全运行至关重要。

来自芬兰赫尔辛基大学物理系的Andrea E. Sand教授等，利用钨<100>通道的钨离子阻挡能来预测W的沟道范围，而离子阻挡能可用含时的密度泛函理论（TDDFT）计算获得，所预测出的结果与实验结果非常一致。他们使用TDDFT的模拟值和实验值均明显低于常用的SRIM模型和Firsov模型预测给出的随机轨迹的平均截止功率。对于芯电子较多的体系，电子停止功率的预测值饱和提供了强有力的证据，说明能量耗散通道已经被考虑在内。此外，与SRIM值相比，TDDFT计算的收敛性对于正确预测碰撞级联相关的轰击体能量范围具有更可靠的指示作用，特别是在本研究所作的确定晶向上的轰击体能量范围预测。这项工作验证了TDDFT计算方法在确定钨靶中重W轰击体的电子阻挡方面的适用性，以及局部环境对阻挡能大小的显著影响。

该文近期发表于npj Computational Materials 5: 43 (2019)，英文标题与摘要如下，点击左下角“阅读原文”可以自由获取论文PDF。

Heavy ion ranges from first-principles electron dynamics

Andrea E. Sand, Rafi Ullah & Alfredo A. Correa

The effects of incident energetic particles, and the modification of materials under irradiation, are governed by the mechanisms of energy losses of ions in matter. The complex processes affecting projectiles spanning many orders of magnitude in energy depend on both ion and electron interactions. Developing multi-scale modeling methods that correctly capture the relevant processes is crucial for predicting radiation effects in diverse conditions. In this work, we obtain channeling ion ranges for tungsten, a prototypical heavy ion, by explicitly simulating ion trajectories with a method that takes into account both the nuclear and the electronic stopping power. The electronic stopping power of self-ion irradiated tungsten is obtained from first-principles time-dependent density functional theory (TDDFT). Although the TDDFT calculations predict a lower stopping power than SRIM by a factor of three, our result shows very good agreement in a direct comparison with ion range experiments. These results demonstrate the validity of the TDDFT method for determining electronic energy losses of heavy projectiles, and in turn its viability for the study of radiation damage.