Computer Simulation Studies Of Radiation Damage Stability (Fission-Track Annealing) and He Diffusion In Apatite Materials

天然和合成磷酸钙（磷灰石）中辐射损伤和气体扩散的稳定性对环境、地球科学和工程问题（包括核废料储存）至关重要。解读地球上地壳岩石的热历史是理解地球动力学过程、长期景观演变和评估沉积盆地油气成熟度的基本要求。热历史重建的关键方法是利用磷灰石，测量核辐射损伤（裂变径迹FT）和放射性氦（U-Th）/He计时法的积累和稳定性。样品数据的解释需要精确了解径迹和氦在高温下的稳定性，目前这是从不同时间-温度条件下的部分径迹缩短（退火）或氦损失的经验测量得出的。磷酸钙（磷灰石）晶格中不同的取代会产生FT稳定性和气体扩散的差异，本项目将采用一种平行的方法，开发和使用一系列互补的计算方法来研究磷酸钙材料中的辐射损伤和气体扩散，其中的关键问题是：开发磷酸钙晶格中取代的杂质阳离子和阴离子相互作用的模型;纯晶格和有缺陷晶格中He扩散的模拟模拟不同磷灰石结构中核裂变径迹的产生和退火过程。该项目的成果将是在原子尺度上对成分对核裂变径迹的形成和稳定性以及扩散的影响有更深入和详细的了解。氦在磷灰石，一种方法，可随后应用于研究日益复杂的材料中的损伤和扩散。

The stability of radiation damage and the diffusion of gas in natural and synthetic calcium phosphate (apatite) is of major importance to environmental, geoscience and engineering problems, including nuclear waste storage. Deciphering the thermal histories of Earth's upper crustal rocks is an essential requirement for understanding geodynamic processes, long-term landscape evolution and in assessing hydrocarbon maturity in sedimentary basins. Key methods in thermal history reconstruction utilise apatite, measuring the accumulation and stability of nuclear radiation damage (fission-tracks FT) and of radiogenic helium - (U-Th)/He chronometry. Interpretation of sample data requires precise knowledge of the stability of the tracks and helium at elevated temperatures which at present is derived from empirical measurement of the fractional track shortening (annealing) or helium loss under different time - temperature conditions. Varying substitutions in the calcium phosphate (apatite) lattice produce differences in the FT stability and gas diffusion.This project will employ a parallel approach developing and employing a range of complementary computational methods to investigate radiation damage and gas diffusion in calcium phosphate materials, where the key issues are:The development of models for the interaction of impurity cations and anions, substituted in the calcium phosphate lattice;Modelling of He diffusion in the pure and defective lattice;Simulation of the processes of generation and annealing of nuclear fission tracks in different apatite structures.The outcome of the project wi4 be an improved and detailed understanding on the atomic scale of the influence of composition on the formation and stability of nuclear fission tracks and the diffusion of helium in apatite, an approach which can be applied subsequently to study damage and diffusion in increasingly complex materials.