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首页> 外文期刊>Journal of Physics. Condensed Matter >Multi-scale simulation of structural heterogeneity of swift-heavy ion tracks in complex oxides
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Multi-scale simulation of structural heterogeneity of swift-heavy ion tracks in complex oxides

机译：复杂氧化物中快速重离子轨道结构异质性的多尺度模拟

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摘要

Tracks formed by swift-heavy ion irradiation, 2.2 GeV Au, of isometric Gd_2Ti_2O_7 pyrochlore and orthorhombic Gd _2TiO_5 were modeled using the thermal-spike model combined with a molecular-dynamics simulation. The thermal-spike model was used to calculate the energy dissipation over time and space. Using the time, space, and energy profile generated from the thermal-spike model, the molecular-dynamics simulations were performed to model the atomic-scale evolution of the tracks. The advantage of the combination of these two methods, which uses the output from the continuum model as an input for the atomistic model, is that it provides a means of simulating the coupling of the electronic and atomic subsystems and provides simultaneously atomic-scale detail of the track structure and morphology. The simulated internal structure of the track consists of an amorphous core and a shell of disordered, but still periodic, domains. For Gd_2Ti_2O_7, the shell region has a disordered pyrochlore with a defect fluorite structure and is relatively thick and heterogeneous with different degrees of disordering. For Gd_2TiO _5, the disordered region is relatively small as compared with Gd _2Ti_2O_7. In the simulation, 'facets', which are surfaces with definite crystallographic orientations, are apparent around the amorphous core and more evident in Gd_2TiO_5 along [010] than [001], suggesting an orientational dependence of the radiation response. These results show that track formation is controlled by the coupling of several complex processes, involving different degrees of amorphization, disordering, and dynamic annealing. Each of the processes depends on the mass and energy of the energetic ion, the properties of the material, and its crystallographic orientation with respect to the incident ion beam.
机译：利用热尖峰模型结合分子动力学模拟，对等离子Gd_2Ti_2O_7烧绿石和正交晶的Gd_2TiO_5进行了快速重离子辐照（2.2 GeV Au）形成的轨迹。使用热峰值模型来计算随时间和空间的能量耗散。使用从热尖峰模型生成的时间，空间和能量分布，进行了分子动力学模拟，以模拟轨道的原子尺度演化。这两种方法相结合的优点是，使用连续体模型的输出作为原子模型的输入，它提供了一种模拟电子子系统和原子子系统耦合的方法，同时提供了轨道结构和形态。轨道的模拟内部结构由非晶核和无序但仍然是周期性畴的壳组成。对于Gd_2Ti_2O_7，壳区具有无序的烧绿石，萤石结构缺陷，并且相对较厚且不均匀，具有不同的无序度。对于Gd_2TiO _5而言，与Gd _2Ti_2O_7相比，无序区相对较小。在模拟中，“晶面”是具有确定的晶体学取向的表面，在非晶核周围很明显，并且在[010]上比[001]在Gd_2TiO_5中更明显，这表明了辐射响应的取向依赖性。这些结果表明，磁道的形成受几个复杂过程的耦合控制，这些过程涉及不同程度的非晶化，无序和动态退火。每个过程都取决于高能离子的质量和能量，材料的特性及其相对于入射离子束的晶体学取向。

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