Monoclinic arrangement definition

Crystalline kris-ta-bn [ME cristallin, ft. MF L MF, fr. L crystallines, fr. Gk krys-tallinos, fr. krystallos] (15c) adj. A substance (usually solid but can be liquid) in which the atoms or molecules are arranged in a definite pattern that is repeated regularly in three dimensions. Crystals tend to develop forms bounded by definitely oriented plane surfaces that are harmonious with their internal structure. They may belong to any of six crystal systems cubic, hexagonal, tetragonal, orthorhombic, monoclinic, or triclinic. 

The use of the rotation function to study the arrangement of subunits in spherical viruses has led to some interesting discussion. A preliminary analysis of the X-ray data on the satellite tobacco necrosis virus crystals indicated that these might have octahedral rather than icosahedral symmetry. However, all solutions to the rotation function originally considered involved a particle two-fold axis parallel to the monoclinic two-fold axis. It has been demonstrated that if this restriction is relaxed, octahedral symmetry is generated in the Patterson by the packing of two virus particles of icosahedral symmetry, This special icosahedral solution appears to be definitely preferable to the octahedral solution. 

McMurchy examined six varieties of chlorite by the X-ray powder technique. He confirmed Pauling s basic structure and derived a total of 16 possible theoretical stacking arrangements based on a monoclinic unit cell with jS 97°. His proposed structures were equally divided between two-layer structures of space group C2jc and one-layer structures of space group C2/w. He narrowed the possibilities down to one two-layer and one one-layer structure by comparison of observed and calculated intensities. He was unable to decide between these structures because of the absence of the definitive A 3 reflections on his powder films, but he favored the two-layer polytype. 

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