A New Type of Crystal: Dislocation-Helix Array of Cholic Acid

Wang, XD (Wang, Xudong)^{[ 1 ]} ; Lu, Y (Lu, Yon)^{[ 2 ]}

CRYSTAL RESEARCH AND TECHNOLOGY, 2019, 文献号: 1900059

DOI: 10.1002/crat.201900059

摘要

All crystals reported to date have been 3D lattice arrays of atoms, ions, or molecules. Here, however, it is reported that a prismatic crystal of cholic acid (CA) is a dislocation-helix array composed of 1D dislocation helices with a pitch of 13.4 mu m. In the cross-section of the array, there are two vectors, with lengths of 51.1 and 31.5 angstrom, which correspond to the inter-dislocation-helix distances. In the array, the dislocation helices, whose interhelix distances are the vectors, diffract the incident X-ray beam and produce diffracted beams that fall on the 2D detector to form diffraction spots, which compose a 2D lattice in all the single-crystal X-ray diffraction patterns of the prismatic crystal of CA. More interestingly, along the helices in the array, the CA molecules, whose intermolecular distance is the pitch of the helix, diffract visible light; and, in a laser confocal scanning microscopy image of the crystal, one right-handed double-stranded diffraction helix (which is caused by visible-light diffraction) is visible around the center line of the prismatic crystal. From what is known, this is the first report of visible-light diffraction by a crystal.