== Phonons in Perfect 4H-SiC

我们将声子被分为两类讨论：
  极性可以忽略的声子模式（即极性为零或非常弱的声子），在拉曼散射过程中它们的电极性造成的效应可以忽略；
  强极性声子模式，在拉曼光谱中电极性效应是可观测的，不可以被忽略。

These phonons were categorized into two groups and discussed separately, according to their electrical polarities:
  phonons with negligible polarities (i.e., zero or very weak electrical polarity),
    where atoms of the same species vibrated in opposite directions,
    resulting in effective cancellation of electrical polarization during the Raman process
    (gray lines in @figure-discont);
  and phonons with strong polarities
    where atoms of the same species vibrated in phase,
    resulting in strong electrical polarization and observable effects in Raman spectra
    (colored lines in @figure-discont).

#include "figure-discont.typ"
#include "non-polar/default.typ"
#include "polar/default.typ"
