Frustrated pretransitional phenomena in aperiodic composites


This paper reports on symmetry breaking in the aperiodic inclusion compound n-octadecane/urea and its isotopomer n-octadecane/urea-d(4). The high-symmetry phase is described by a hexagonal rank-4 superspace group. Pretransitional phenomena in this crystallographic superspace reveal competing short-range-ordering phenomena within the high-symmetry phase. Very high-resolution diffraction data show that critical scattering appears at inequivalent points within the four-dimensional Brillouin zone, although the first phase transition at T-c1 near 158 K implies the condensation at only one of those points. The resulting superspace group remains of dimension 4. Two other phase transitions are reported at T-c2 = 152.8(4) K and T-c3 = 109(4) K in n-octadecane/urea-d(4). The two low-symmetry phases that arise are described by rank-5 superspace groups.


Citation: Mariette, C., Frantsuzov, I., Wang, B., Guerin, L., Rabiller, P., Hollingsworth, M. D., & Toudic, B. (2016). Frustrated pretransitional phenomena in aperiodic composites. Physical Review B, 94(18), 9. doi:10.1103/PhysRevB.94.184105


Urea Inclusion-Compounds, X-Ray-Diffraction, Diffuse-Scattering, Phase-Transition, N-Paraffins, Compounds Oc(Nh2)2+Cnh2N+2