Orientational Disorder in Adamantane and Adamantanecarboxylic Acid

Abstract

The molecular crystals adamantane, C H , and adamantanecarboxylic acid, C H COOH, undergo order-disorder phase transitions at 208 and 250 K, respectively. Reverse Monte Carlo refinement of total neutron scattering data collected from deuterated samples immediately above these phase transitions shows that the high-temperature phases are well described by models in which the adamantyl groups are disordered over two sites. No correlation between the orientations of neighbouring molecules is observed. These results demonstrate that the intermolecular potential energy of these materials depends strongly on the orientation of the reference molecule but only very weakly on the orientations of its neighbours.

Polymorphism of 1,3-X-adamantanes (X = Br, OH, CH3) and the crystal plastic phase formation ability

“…, are close to the volume change at the ordered to orientationally disordered transition for some adamantane derivatives. [24][25]59] From the experimental pressure-temperature phase diagrams of 13DMA and 13DOHA, it becomes clear that increasing pressure gives rise to an increase of the temperature domain of the plastic phase I (see Figure 1), as is usually observed for the studied plastic crystal materials so far. [62,64,69] This means that the ratio between the II to I and I to Liquid temperatures, T II-I /T I-L , continuously decreases when increasing pressure.…”

“…As a consequence, the hydrogen atom linked to the oxygen lies on two symmetrical positions with an equal fractional occupancy of 50%. Three kinds of hydrogen bond configuration in adamantanes have been reported: dimer as for 1adamantanecarboxylic acid [59], tetramer as for 1-adamantanol [60] and hexamer as for 1-adamantane-methanol [23]. For 13DOHA, as for the 1-adamantane-methanol [23], the hydrogen bonds involve the O-H dipoles of six neighbouring molecules in a threedimensional hydrogen bonding hexagonal network (see Figure 3, bottom panel) which is perpendicular to the c axis.…”

Polymorphism and solid–solid phase transitions of hydrogen bonded 2-adamantanol and 2-methyl-2-adamantanol compounds

“…[2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] The pristine adamantane compound (C 10 H 16 ) is one of the most studied examples of organic molecular crystals which undergoes a first-order orderdisorder phase transition, from an ordered low-temperature phase (P4 ¯21 c, Z = 2) 21 to an orientationally disordered (OD) phase (Fm3 ¯m, Z = 4), which displays a translational facecentered cubic lattice with the center of masses of the molecules sitting at the lattice nodes but orientationally disordered. 22,23 Adamantane derivatives, with simple single 3692 | CrystEngComm, 2022, 24, 3692-3700 This journal is © The Royal Society of Chemistry 2022 a Grup de Caracteritzacio de Materials, Departament de Fisica and Barcelona Research Center in Multiscale Science and Engineering, Universitat Politecnica de Catalunya, EEBE, Campus Diagonal-Besos, Av. Eduard Maristany 10-14, 08019 Barcelona, Catalonia, Spain.…”

Neutron scattering study of the orientational disorder in potassium cyanide

“…In the past this typically meant analysis of configurations generated by the molecular dynamics simulation method, but from an experimental approach this is now possible using neutron total scattering data together with the Reverse Monte Carlo (RMC) method [17][18][19]. One recent example of this technique for studying orientational disorder was an investigation of crystalline adamantane [20], but in this case the molecules were found to be confined to be in either of two preferred orientations rather than with a continuous distribution. If the orientational probability distribution function is expanded in terms of orthonormal functions,…”