Proceedings of the Royal Society of London Series A Containing Papers of a Mathematical and Physical Character · 1933 · 48 citations · 0 references
Natural SciencesChemistryCrystal StructureOrganic ChemistryPhysical ChemistryCrystal ChemistryCrystalline MaterialsCrystallographyMolecular SymmetryX-ray CrystallographyX-ray DiffractionCrystalline StructureDensityMolecular VolumeOrganic CrystalsUnit Cell DeterminationUnit Cell GeometryUnit Cell ParametersX-ray Diffraction Analysis
Abstract Crystal Data. Naphthalene.—C10H8. Melting point 80° C. Density 1·152 (calc. 1·172). Monoclinic prismatic, a = 8·29, b = 5·97, c = 8·68 A., β = 122·7°. Space group C2λ5 (P21/a). Two molecules per unit cell. Molecular symmetry, centre. Molecular volume, 362 A3. Total number of electrons per unit cell = F(000) = 136. Experimental—Measurements of Intensities. When a small single crystal is placed completely in an X-ray beam, the integrated reflection is proportional to the mass of the crystal, if the latter is sufficiently small. Although fairly large crystals of naphthalene can easily be obtained, the aim in this work has been to carry out the measurements on specimens small enough for this proportionality to hold good. With soft, organic crystals of the hydrocarbon type, the size required for reliable results is found to be of order of 0·1 milligrams.