Pseudo-weak-phase-object approximation in high-resolution electron microscopy. I. Theory
Pseudo-weak-phase-object approximation in high-resolution electron microscopy. I. Theory
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DOI：
10.1107/s0108767385000800
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发表时间：
1985-07
期刊：
影响因子：
--
通讯作者：
F. H. Li;D. Tang
中科院分区：
文献类型：
--
作者：
F. H. Li;D. Tang
本文根据Cowley和Moodie [Acta Cryst.（1957），10，609-619]的动态电子衍射理论，导出了用投影电势分布和样品厚度表示的多束象强度的新公式。根据这个公式，弱相物体近似不成立的晶体可以用赝弱相物体近似（PWPOA）处理，直到一定的临界厚度。在这里，真实的晶体被它的想象的同质异能素所取代，其中组成重原子的行为比真实的晶体中的原子轻，反之亦然。通过对氯化酞菁铜的PWPOA计算结果与多层法计算结果的比较，验证了PWPOA的有效性。
On the basis of the dynamical electron diffraction theory of Cowley & Moodie [Acta Cryst. (1957), 10, 609-619], a new formula has been derived for the multiple-beam image intensity expressed in terms of the projected potential distribution as well as the specimen thickness. According to this formula, crystals for which the weak-phase-object approximation does not hold can be treated by the pseudo-weak-phase-object approximation (PWPOA) up to a certain critical thickness. Here the real crystal is replaced by its imaginary isomorph, where the constituent heavy atoms behave as lighter atoms than those of the real crystal, and vice versa. The validity of the PWPOA is discussed and confirmed by the comparison of the images of chlorinated Cu phthalocyanine calculated with PWPOA and the multislice method.