High-pressure polymorphism in pyridine.

ABSTRACT: Single crystals of the high-pressure phases II and III of pyridine have been obtained by in situ crystallization at 1.09 and 1.69 GPa, revealing the crystal structure of phase III for the first time using X-ray diffraction. Phase II crystallizes in P2₁2₁2₁ with Z' = 1 and phase III in P4₁2₁2 with Z' = ½. Neutron powder diffraction experiments using pyridine-d₅ establish approximate equations of state of both phases. The space group and unit-cell dimensions of phase III are similar to the structures of other simple compounds with C _2v molecular symmetry, and the phase becomes stable at high pressure because it is topologically close-packed, resulting in a lower molar volume

SUBMITTER: Giordano N 

PROVIDER: S-EPMC6949594 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature