Institut de Physique de Rennes, UMR UR1-CNRS 6251, Université de Rennes 1, 35042 Rennes, France.
J Chem Phys. 2011 Nov 28;135(20):204505. doi: 10.1063/1.3663711.
High-resolution studies of the host-guest inclusion compound n-hexadecane/urea are reported at atmospheric pressure, using both cold neutrons and x-ray diffraction. This intergrowth crystal presents a misfit parameter, defined by the ratio c(h)/c(g) (c(host)/c(guest)), which is temperature independent and irrational (γ = 0.486 ± 0.002) from 300 to 30 K. Three different structural phases are reported for this aperiodic crystal over this temperature range. The crystallographic superspaces are of rank 4 in phases I and II, whereas phase III is associated with an increase in rank to 5, with a supplementary misfit parameter (δ = 0.058 ± 0.002) that is constant throughout this phase. The superspace group of phase I is hexagonal P6(1)22(00γ) down to T(c1) = 149.5 ± 0.5 K; phase II, which persists down to T(c2) = 127.8 ± 0.5 K is orthorhombic P2(1)2(1)2(1)(00γ), and phase III is orthorhombic P2(1)2(1)2(1)(00γ)(00δ).
报道了在常压下使用冷中子和 X 射线衍射对主体客体包合物正十六烷/尿素的高分辨率研究。这种共生晶体具有一个不匹配参数，由 c(h)/c(g)（c(主体)/c(客体)）的比值定义，该参数在 300 到 30 K 之间是温度独立且无理的（γ=0.486±0.002）。在这个温度范围内，该非周期性晶体报告了三种不同的结构相。在相 I 和 II 中，晶体学超空间的秩为 4，而在相 III 中，秩增加到 5，并有一个附加的不匹配参数（δ=0.058±0.002），在整个相 III 中保持不变。相 I 的超空间群为六角形 P6(1)22(00γ)，直至 T(c1)=149.5±0.5 K；相 II 一直持续到 T(c2)=127.8±0.5 K，为正交 P2(1)2(1)2(1)(00γ)，相 III 为正交 P2(1)2(1)2(1)(00γ)(00δ)。
