The interpretation of polycrystalline coherent inelastic neutron scattering from aluminium.
The interpretation of polycrystalline coherent inelastic neutron scattering from aluminium.
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DOI：
10.1107/s0021889813023728
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发表时间：
2013-12-01
影响因子：
6.1
通讯作者：
Taylor JW
中科院分区：
文献类型：
--
作者：
Roach DL;Ross DK;Gale JD;Taylor JW
这里提出的是一种方法，通过该方法可以测量多晶样品的Q依赖色散动力学（并用于生成晶格动力学模型）。该方法类似于单晶样品色散曲线的测量。本文提出了一种解释和分析多晶体中子相干非弹性散射的新方法。本文模拟了任意晶体系统的晶格模型的单声子相干非弹性散射。单声子分量的特征在于尖锐的特征，例如，由允许单声子散射的（Q，ω）区域的边界确定。这些特征可以用在测量的总相干非弹性截面中明显的相同特征来识别，其中的其他分量（多声子或多次散射）没有显示出尖锐的特征。然后可以放宽模型的参数以改善模型与实验之间的拟合。这种方法在没有单晶的情况下特别有用。为了测试这种方法，使用MARI光谱仪（ISIS）测量了多晶铝的聚CINS，因为晶格动力学模型和测量的色散曲线都可用于这种材料。所使用的模型包括一个简单的Lennard-Jones模型，该模型适合于该材料的弹性常数加上一些嵌入原子法力场。所获得的协议表明，该方法证明应该是有效的，在其他材料的单晶色散曲线是不可用的开发模型。
Presented here is a method by which Q-dependent dispersive dynamics may be measured (and used to generate a lattice dynamical model) for polycrystalline samples. This method is analogous to the measurement of dispersion curves for single-crystal samples. A new approach to the interpretation and analysis of coherent inelastic neutron scattering from polycrystals (poly-CINS) is presented. This article describes a simulation of the one-phonon coherent inelastic scattering from a lattice model of an arbitrary crystal system. The one-phonon component is characterized by sharp features, determined, for example, by boundaries of the (Q, ω) regions where one-phonon scattering is allowed. These features may be identified with the same features apparent in the measured total coherent inelastic cross section, the other components of which (multiphonon or multiple scattering) show no sharp features. The parameters of the model can then be relaxed to improve the fit between model and experiment. This method is of particular interest where no single crystals are available. To test the approach, the poly-CINS has been measured for polycrystalline aluminium using the MARI spectrometer (ISIS), because both lattice dynamical models and measured dispersion curves are available for this material. The models used include a simple Lennard-Jones model fitted to the elastic constants of this material plus a number of embedded atom method force fields. The agreement obtained suggests that the method demonstrated should be effective in developing models for other materials where single-crystal dispersion curves are not available.