Multiple cascade radiation damage simulations of pyrochlore
Multiple cascade radiation damage simulations of pyrochlore
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DOI：
10.1080/08927022.2020.1805449
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发表时间：
2020-10
影响因子：
2.1
通讯作者：
Adam Archer;H. R. Foxhall;Neil L. Allan;Jonathan Shearer;Dsd Gunn;John H. Harding;I. Todorov;Karl P. Travis;J. Purton
中科院分区：
文献类型：
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作者：
Adam Archer;H. R. Foxhall;Neil L. Allan;Jonathan Shearer;Dsd Gunn;John H. Harding;I. Todorov;Karl P. Travis;J. Purton
本文报道了高温超导体Gd_2Ti_2O_7和Gd_2Zr_2O_7以及固溶体Gd_2（Zr_xTi_1-x）_2O_7（x = 0.25，0.50，0.75）中多重辐射损伤级联的分子动力学模拟。使用360，448个原子的模拟单元，对于每个化合物，在10 ns的总时间内模拟2200个衰变事件，每个反冲铀原子（初级撞击原子）被分配5 keV的初始动能。生成的结构进行了分析，使用Steinhardt局部序参数。有一个大的增加量的Ti烧绿石与过渡到一个无定形结构，类似于熔体，同时保持当地环境的Ti。计算出的非晶化剂量为20 eV atom−1，与实验结果相比，级联和损伤累积的重叠驱动了非晶化抑制愈合机制。锆酸盐的行为是不同的-每次反冲事件产生的大量阴离子无序之后是愈合和恢复到母烧绿石。在固溶体中，非晶化的开始延迟到以后的时间增加Zr浓度和整体溶胀减少。我们的模拟强调了离子迁移率的重要性，与较弱的Zr-O键，愈合。
ABSTRACT We report molecular dynamics simulations of multiple radiation damage cascades in the pyrochlores Gd2Ti2O7 and Gd2Zr2O7 and the solid solution Gd2(Zr x Ti1–x )2O7 (x = 0.25, 0.50, 0.75). Using a simulation cell of 360,448 atoms, for each compound 2200 decay events are simulated over a total time of 10 ns, with each recoiling uranium atom (primary-knock-on atom) assigned initial kinetic energy of 5 keV. The structures generated are analysed using Steinhardt local order parameters. There is a large increase in volume for the Ti pyrochlore associated with a transition to an amorphous structure which resembles the melt while preserving the local environment of the Ti. The calculated dose for amorphisation is 20 eV atom−1 which compares well with experiment overlap of cascade and damage accumulation drives the amorphisation suppressessing the healing mechanisms. The behaviour of the zirconate is different – the substantial anion disorder produced by each recoil event is followed by healing and reversion to the parent pyrochlore. In the solid solution the onset of amorphisation is delayed to later times on increasing the Zr concentration and overall swelling reduced. Our simulations highlight the importance of ion mobility, associated with the weaker Zr–O bonds, in healing.