The effect of crystal bending on direct phasing of electron diffraction data from cytosine

Limiting conditions for the crystal structure analysis of organics using electron diffraction intensity data from elastically bent microcrystals are shown for a representative aromatic structure, cytosine, C₄H₅N₃O. In a projection down the longest unit-cell axis, the normalized structure-factor magnitudes are greatly changed by slight bends, making the diffraction data useless for crystal structure analysis. This alteration of intensity is less severe for a projection down the shortest cell axis and allows a correct structure analysis for bends comparable to those measured experimentally. The correct crystal orientation, moreover, is only achieved by epitaxial growth and not solution growth.