Lattice Constants of Ultrapure Phenanthrene

Abstract
Ultrahigh-purity phenanthrene has been prepared by multiple zone-refining. To determine if a resistivity anomaly observed at 68°C is associated with a polymorphic transformation, x-ray diffraction scans were made at 26° and 84°C. There is no evidence for a polymorphic transformation over this temperature range, although anisotropic behavior was noted for the thermal expansion coefficients. Precision lattice constants were determined for the monoclinic cell of phenanthrene at 26°C; these are a0=8.4744 Å, b0=6.1720 Å, c0=9.4805 Å, β=98° 01′.