Prediction and characterisation of radiation damage in fluorapatite
Prediction and characterisation of radiation damage in fluorapatite
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DOI：
10.1039/c4ta01707b
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发表时间：
2015-01-01
影响因子：
11.9
通讯作者：
Grimes, Robin W.
中科院分区：
文献类型：
--
作者：
Jay, Eleanor E.;Fossati, Paul C. M.;Grimes, Robin W.
分子动力学模拟，结合一组经典的对势，已被用来检查模拟辐射损伤级联在氟磷灰石结构。随后评估了损伤区域的恢复能力，以及损伤对确定晶体结构的重要结构单元（即磷酸盐四面体和钙元棱镜）的影响。通过确定碰撞级联过程中磷配位环境的变化来考虑损伤。这表明PO4单元基本上保留了下来，即使在辐射损伤的峰值，也只观察到很少数量的低于或超过配位的磷酸盐单元。通过比较，材料的受损区域显示出磷酸盐多面体拓扑结构的显著变化，其聚合形成长达7个单位的链。值得注意的是，氟磷灰石结构特征的氟通道和由结构的钙元棱镜定义的氟通道在整个过程中几乎保持完整。这意味着受损区域可以被表征为与原始未受损磷灰石结构的规则特征交错的无定形磷酸盐链。
Molecular dynamics simulations, used in conjunction with a set of classical pair potentials, have been employed to examine simulated radiation damage cascades in the fluorapatite structure. Regions of damage have subsequently been assessed for their ability to recover and the effect that damage has on the important structural units defining the crystal structure, namely phosphate tetrahedra and calcium meta-prisms. Damage was considered by identifying how the phosphorous coordination environment changed during a collision cascade. This showed that PO4 units are substantially retained, with only a very small number of under or over coordinated phosphate units being observed, even at peak radiation damage. By comparison the damaged region of the material showed a marked change in the topology of the phosphate polyhedra, which polymerised to form chains up to seven units in length. Significantly, the fluorine channels characteristic of the fluorapatite structure and defined by the structure's calcium meta-prisms stayed almost entirely intact throughout. This meant that the damaged region could be characterised as amorphous phosphate chains interlaced with regular features of the original undamaged apatite structure.