Structural characterization of diatomic fluids by diffraction studies

Abstract

The study of spatial features in diatomic liquids and gases is reviewed with a specific emphasis on experimental measurements using neutron and x-ray diffraction. The formalism for defining the pair-correlation function is described and related to the liquid structure factor which can be extracted from the diffraction measurements. Different molecular systems can be classified in terms of the intermolecular potential which depends on various factors related to geometrical conformation, electron density distribution and anisotropy. The increased complexity over monoatomic systems gives rise to new phenomena associated with orientational correlation of molecular axes.The techniques of neutron and x-ray diffraction are critically reviewed and a full list of published work (plus some unpublished results) is presented. The experimental measurements are analysed and compared with the results of computer simulations using model potentials. It is noted that several systems (e.g. N2. 0,, F2, C O ) have a relatively simple behaviour but others (e.g. Cl,, Br,, 12) are only just on the point of being properly understood, while the hydrogen-bonded liquids (e.g. HF, HCl) still pose many problems that currently remain unresolved. The review ends with a brief consideration of likely developments in the foreseeable future. This review was received in July 1990.*The basic concepts which subsequently lead to the production of thin review can be traced back to a meeting on diatomic liquids held in Rome in October 1983.

Multiscale Studies on Ionic Liquids

“…σ in Table ) oscillating between regions of enhanced and depleted density . The diatomic (H 2 , N 2 , O 2 , halogen) and triatomic (sc-CO 2 ) liquids, though being VDW model, are nonspherical, and electron densities are inhomogeneous. Classic molecular liquids, such as water, − methanol, methylamine, and ammonia, possess more well-defined structure via a well-defined H-bonding network, such as the water tetrahedral H-bonding network, and other solvents via a nontetrahedral H-bonding network .…”

Effect of available volumes on radial distribution functions

“…dial distribution functions rdfs , are a common tool used in molecular dynamics studies to describe the distribution of solvent molecules around a solute. They have the advantage of being directly related to observable experimental quantities 1 -neutron and X-ray scattering intensitiesalthough the full set of atom᎐atom rdfs is often difficult to extract from experiments on molecular systems. A great deal of information has been obtained from the position, intensity, and width of the various peaks exhibited by rdfs.…”

On the Microscopic Structure of Liquid Hydrogens

“…Instead, no reliable information was available on liquid hydrogens till recently [16]. In fact, in order to correct the neutron diffraction data for inelasticity effects, researchers have mostly used the so-called Placzek correction procedure [17].…”