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@@ -45,21 +45,35 @@ It should be noted, however, that the observability in Raman experiment depends
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因此,拉曼张量的大小可以在进一步的第一性原理计算之前给出,结果总结在表中。
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我们的结果表明,756 附近的峰应该比其它峰具有更强的拉曼强度。
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A method to estimate the magnitudes of the Raman tensors based on symmetry analysis was proposed.
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A method to rapidly estimate the magnitudes of the Raman tensors was proposed (see appendix for details).
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This approach is founded on the symmetry analysis and incorporates the assumption
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that the majority contribution of each atom to the Raman tensor is determined by its nearest neighbors
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(denoted as $a_i$),
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while contributions from more distant atoms are considered small (denoted as $epsilon_i$, $eta_i$, and $zeta_i$).
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Additionally, we neglect the absolute differences in amplitudes of the same type of atoms in a phonon mode,
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focusing only on their vibrational directions.
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Consequently, the Raman tensors of the calculated phonon modes can be estimated
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before additional first-principles computations (see appendix for details),
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and the results are summarized in @table-nopol.
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The parameters $a_i$ exhibit significantly larger absolute values compared to $epsilon_i$, $eta_i$, and $zeta_i$,
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indicating the E#sub[2] mode at 756.25 cm#super[-1] in simulation (mode 8)
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possess a much higher Raman intensity than the others.
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that the primary contribution from each atom to the Raman tensor arises from its nearest neighbors (denoted as $a_i$),
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while contributions from more distant atoms are much smaller (denoted as $epsilon_i$, $eta_i$, and $zeta_i$).
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Furthermore, we neglect the absolute amplitude differences among atoms of the same type within a phonon mode,
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considering only their vibrational directions.
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This enables a preliminary estimation of the Raman tensor magnitudes prior to detailed first-principles calculations,
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with the results summarized in @table-nopol.
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Our analysis indicates that the E#sub[2] mode at 756.25 cm#super[-1] in simulation (mode 8)
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should possess a much higher Raman intensity than the others.
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我们使用第一性原理计算得到了拉曼张量的大小,并与我们的结果进行了比较。
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#include "table-nopol.typ"
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我们使用第一性原理计算得到了频率和拉曼张量的大小,并与我们的结果进行了比较。
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声子频率和拉曼张量的大小被使用第一性原理计算,并与实验结果和理论预测进行了比较(@table-nopol)。
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计算的声子频率与实验数据有很好的吻合,误差在 2-5% 之间,这个误差可能是由于 PBE 泛函对原子间力的低估(cite)。
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计算的拉曼张量也与实验和理论结果基本一致,这包括
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强度最高的模式 E#sub[2] 在 776 cm#super[-1] 的实验(模式 8),
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其次是四个强度较低但在实验中清晰可见的模式,
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包括 E#sub[2] 模式在 195.5 cm#super[-1](模式 1)和 203.3 cm#super[-1](模式 2),
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E#sub[1] 模式在 269.7 cm#super[-1](模式 3),
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和 A#sub[1] 模式在 609.5 cm#super[-1](模式 6)。
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在 746 cm#super[-1](模式 7)计算的 E#sub[1] 模式
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和 756.25 cm#super[-1](模式 9)计算的 E#sub[2] 模式
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被预测具有更弱的拉曼强度,并且位于最强模式(模式 8)附近,使得它们在实验光谱中难以区分。
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此外,在 812.87 cm#super[-1](模式 10)计算的 A#sub[1] 模式
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在基面极化配置(xx 和 yy,仅为 0.01)中具有非常弱的拉曼强度,
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但当偏振沿 z 轴时(1.78)则显示出可观的强度。
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The Raman tensors and frequencies of the negligible-polar phonons were calculated using first-principles methods,
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and the results are compared with both experimental data and theoretical predictions (@table-nopol).
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@@ -97,8 +111,6 @@ Besides, there are small peeks at xxx,
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// 在论文中我们这样来称呼:phonon 对应某一个特征向量,而 modes 对应于一个子空间。
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// 也就是说,简并的里面有两个或者无数个 phonon,但只有一个 mode
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#include "table-nopol.typ"
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#include "figure-raman.typ"
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// TODO: 解释为什么 E1 可以看到
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