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Ab initio calculations of the rate of carrier trapping and release at dopant sites in NaI: TI beyond the harmonic approximation

机译：AB Initio计算Nai掺杂位点的载体捕获和释放速率的计算：Ti超出谐波近似

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摘要

We present ab initio calculations of electron capture and release coefficients as a function of temperature for Tl dopants in the widely used scintillator NaI, which is a soft ionic crystal. The modeled capture and release events occur by transitions mediated by multiple phonon absorption and emission between states with significantly different local geometries around the trapping site. We demonstrate that such transitions are not well-described by the normal harmonic approximation to the nuclear dynamics. We go beyond the harmonic approximation by numerically solving the vibrational Schroedinger equation for the motion along/of a single effective phonon coordinate. The localized trapped state is not correctly described by semilocal density functionals, so we employ a global hybrid functional tuned to reproduce the band gap and lattice constant of the host material. Our calculations, which combine plane-wave and embedded cluster electronic structure methods are in reasonable agreement with available experimental data for detrapping and predict an unusual temperature dependence for trapping rates.
机译：我们提出了电子捕获和释放系数的AB初始计算，作为掺杂剂在广泛使用的闪烁体Nai中的温度的函数，这是一种软离子晶体。所建模的捕获和释放事件通过在捕获部位周围具有明显不同的局部几何形状的状态之间的多个声子吸收和排放的过渡发生。我们证明，这种过渡不是通过对核动力学的正常谐波近似的良好描述。通过数值求解沿着单个有效的声子坐标的运动的振动斯克罗登格方程来超越谐波近似。通过半透明密度功能不正确描述局部捕获状态，因此我们采用全局混合功能调谐，以再现主体材料的带隙和晶格常数。我们将平面波和嵌入式集群电子结构方法组合的计算是合理的与可用的实验数据一致，用于贬低和预测对诱捕速率的不寻常的温度依赖性。

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  • 来源
    《Physical review》 |2020年第2期|024304.1-024304.11|共11页
  • 作者

    Micah P. Prange; Niranjan Govind; Sebastien N. Kerisit;

  • 作者单位

    Physical Sciences Division Physical and Computational Sciences Directorate Pacific Northwest National Laboratory Richland Washington 99354 USA;

    Environmental Molecular Sciences Division Earth and Biological Sciences Directorate Pacific Northwest National Laboratory Richland Washington 99354 USA;

    Physical Sciences Division Physical and Computational Sciences Directorate Pacific Northwest National Laboratory Richland Washington 99354 USA;

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