Intermolecular interactions in solid benzene

Abstract

The lattice dynamics and molecular vibrations of benzene and deuterated benzene crystals are calculated from force constants derived from density-functional theory ͑DFT͒ calculations and compared with measured inelastic neutron-scattering spectra. A very small change ͑0.5%͒ in lattice parameter is required to obtain real lattice-mode frequencies across the Brillouin zone. There is a strong coupling between wagging and breathing modes away from the zone center. This coupling and sensitivity to cell size arises from two basic interactions. Firstly, comparatively strong interactions that hold the benzene molecules together in layers. These include an intermolecular interaction in which H atoms of one molecule link to the center of the aromatic ring of a neighboring molecule. The layers are held to each other by weaker interactions, which also have components that hold molecules together within a layer. Small changes in the lattice parameters change this second type of interaction and account for the changes to the lattice dynamics. The calculations also reveal a small auxetic effect in that elongation of the crystal along the b axis leads to an increase in internal pressure in the ac plane, that is, elongation in the b direction induces expansion in the a and c directions.

Reassignment of the Vibrational Spectrum of Benzimidazole

“…This is consistent with the fact that no intense overtones are found in this region of the INS spectrum of benzene. 13 Furthermore, the benzimidazole band at 852 cm -1 remains in the benzimidazole-d 2 INS, at 850 cm -1 , in contradistinction to the IR data. The impact of deuteration on this band, which appears so clear-cut from the IR, is less so from the INS data.…”

Colloidal stability of carboxylated iron oxide nanomagnets for biomedical use

“…All the three vibrations require more energy to excite in the adsorbed state, showing that the aromatic ring is firmly connected with the MNP surface, probably lying flat on it. There are two additional bands at frequencies of 1575 and 1497 cm -1 , characteristic of the so called aromatic ring breathing [26] that do not change their position upon adsorption, but become resolvable in the spectra only after decreasing the intensity of the asymmetric stretching vibration of -COO -at 1539 cm -1 . The stretching and contraction of the ring is not influenced by the adsorption, which also supports the probability of lying GA molecules on the surface.…”

Solid–liquid interfacial free energies of benzene

“…From the illustrations of the unit cell of benzene provided in Refs. [23,25] and its parameters (7.034, 7.460, 9.666 Å ) at 270.15 K [24], which is closer to our temperatures, one may evaluate the shortest distance between two molecules belonging to the same unit cell, which is 5.1266 Å , and consider it as the shortest length of broken bonds d sðminÞ . With this shortest value of d s substituted in Eq.…”

“…[23,24] the parameters of the unit cell are provided for 4.2 and 270.15 K, respectively; furthermore in Ref. [23] an illustration of the unit cell showing the relative disposition and orientation of the molecules is depicted, which has been used very recently [25]. Moreover, MD simulation [18] has proven that under constant atmospheric pressure the structure of solid benzene is stable up to 290 K-well above the melting temperature (278.5 K).…”