1.
J Chem Phys
; 136(10): 104507, 2012 Mar 14.
Article
in English
| MEDLINE
| ID: mdl-22423848
ABSTRACT
n-Heptane/urea is an aperiodic inclusion compound in which the ratio of host and guest repeats along the channel axis is very close to unity and is found to have a constant value (0.981) from 280 K to 90 K. Below 280 K, two phase transitions are observed. The first (T(c1) = 145 K) is a ferroelastic phase transition that generates superstructure reflections for the host while leaving the guest with 1D order. The second (T(c2) = 130 K) is a "phase ordering" transition to a four-dimensional structure (P2(1)11(0ßγ)) with pronounced host-guest intermodulation and a temperature dependent phase shift between guests in adjacent channels.