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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >NMR Shielding in Metals Using the Augmented Plane Wave Method
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NMR Shielding in Metals Using the Augmented Plane Wave Method

机译：使用增强平面波方法的金属NMR屏蔽

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摘要

We present calculations of solid state NMR magnetic shielding in metals, which includes both the orbital and the complete spin response of the system in a consistent way. The latter contains an induced spin-polarization of the core states and needs an all-electron self-consistent treatment. In particular, for transition metals, the spin hyperfine field originates not only from the polarization of the valence s-electrons, but the induced magnetic moment of the d-electrons polarizes the core s-states in opposite direction. The method is based on DFT and the augmented plane wave approach as implemented in the WIEN2k code. A comparison between calculated and measured NMR shifts indicates that first-principle calculations can obtain converged results and are more reliable than initially concluded based on previous publications. Nevertheless large k-meshes (up to 2 000 000 k-points in the full Brillouinzone) and some Fermi-broadening are necessary. Our results show that, in general, both spin and orbital components of the NMR shielding must be evaluated in order to reproduce experimental shifts, because the orbital part cancels the shift of the usually highly ionic reference compound only for simple sp-elements but not for transition metals. This development paves the way for routine NMR calculations of metallic systems.
机译：我们介绍了金属中固态NMR磁屏蔽的计算，以一致的方式包括了系统的轨道响应和完整的自旋响应。后者包含核态的自旋极化，需要全电子自洽处理。特别地，对于过渡金属，自旋超精细场不仅起源于价电子的极化，而且诱导的电子的磁矩使铁芯的s态朝相反的方向极化。该方法基于DFT和WIEN2k代码中实现的增强平面波方法。 NMR位移的计算值与实测值的比较表明，第一性原理计算可以得出收敛的结果，并且比基于先前出版物的初步结论更可靠。尽管如此，仍需要较大的k网格（在整个布里渊区中高达2000000 k点）和一些费米扩展。我们的结果表明，总的来说，必须对NMR屏蔽的自旋分量和轨道分量进行评估，以重现实验位移，因为轨道部分仅对简单的sp元素抵消了通常为高离子参比化合物的位移，而对于简单的sp元素则没有。过渡金属。这一进展为金属系统的常规NMR计算铺平了道路。

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