The contrast of Gjønnes–Moodie (GM) lines which appear in convergent‐beam electron diffraction patterns for non‐symmorphic space‐group crystals is explained using Bloch waves. In the two‐dimensional space groups p2mg and pg the Bloch waves for electron diffraction are described. In both space groups along the Δ line, Bloch waves are arranged as two different types, and it is shown that the two types of Bloch waves do not contribute to the intensity of forbidden reflections. Along the position where the forbidden reflection satisfies the Bragg condition, degeneracies of two Bloch waves are found and it is shown that the degenerated pair of Bloch waves do not contribute to the intensity. These Bloch‐wave results provide a new perspective in the understanding of the contrast mechanism of GM lines previously described using scattering polynomials. They also advance the understanding of Bloch‐wave behaviour in high‐energy electron diffraction.

中文翻译：

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非对称空间群晶体的聚束电子衍射中Gjønnes–Moodie线的波波解释

使用布洛赫波解释了非对称空间群晶体会聚束电子衍射图中出现的Gjønnes-Moodie（GM）线的对比度。在二维空间组中p 2 mg和pg描述了用于电子衍射的布洛赫波。在沿着Δ线的两个空间组中，布洛赫波被布置为两种不同类型，并且显示出两种布洛赫波对禁止反射的强度没有贡献。沿着禁止反射满足布拉格条件的位置，发现了两个布洛赫波的简并性，这表明简并的布洛赫波对对强度没有贡献。这些Blochwave结果为理解先前使用散射多项式描述的GM线的对比度机制提供了新的视角。他们还提高了对高能电子衍射中布洛赫波行为的理解。