On the orientational correlations in the supercooled chloride lithium aqueous solution using the hybrid reverse Monte Carlo simulation

2021 ◽  
pp. 2250021
Author(s):  
Zahira Kachour ◽  
Mohammed Habchi ◽  
Sidi Mohammed Mesli ◽  
Mohammed Ziane ◽  
Mohammed Kotbi
Keyword(s):  
Aqueous Solution ◽  
Monte Carlo ◽  
Water Molecule ◽  
Correlation Functions ◽  
Pair Correlation ◽  
Water Molecules ◽  
Reverse Monte Carlo ◽  
Hydration Shells ◽  
Orientational Correlation ◽  
Orientational Correlation Functions

Employing the Hybrid Reverse Monte Carlo (HRMC) simulation, we compute, using the obtained three-dimensional configurations, the orientational correlations of water molecules in the supercooled 9.26 molal LiCl aqueous solution. This study aims to add relevant structural properties to those obtained in our latest studies and further support our findings. The Li/Cl pair ions hydration shells and the water molecules distribution studied using the Radial Pair Distribution Functions (RPDF), ([Formula: see text]) and ([Formula: see text]) are further described using the Orientational Pair Correlation Functions (OPCF), [Formula: see text] which describes the probability of a water molecule oriented by the Euler angles [Formula: see text], being located at the position [Formula: see text], with respect to another water molecule oriented [Formula: see text] placed at the origin. The high dimensionality of the orientational correlation functions has not presented a calculation disability, as known with several simulations, in the face of the efficiency of the HRMC and the water–water orientational correlation functions showed the dominant impact of ions on the water molecular dipole orientations within the hydration shells and in the hydrogen bonded molecules network.

A Molecular Dynamics Study of Aqueous Solutions

1976 ◽  
Vol 31 (5) ◽  
pp. 463-475 ◽  
Author(s):  
K. Heinzinger ◽  
P. C. Vogel
Keyword(s):  
Molecular Dynamics ◽  
Aqueous Solutions ◽  
Correlation Functions ◽  
Elevated Temperatures ◽  
Pure Water ◽  
Pair Correlation ◽  
Lone Pair ◽  
Water Molecules ◽  
Pair Correlation Functions ◽  
Hydration Shells

Abstract Results of a molecular dynamics study of aqueous solutions of LiJ, LiCl, NaCl, CsCl and CsF are reported. The basic periodic box contained 200 water molecules, 8 cations and 8 anions, equivalent to 2.2 molal solutions. Static properties of the first hydration shells of the ions are discussed in detail on the basis of radial pair correlation functions, average potential energies of the water molecules and pair interaction energy distributions. The calculations lead to the conclusion that in the first hydration shells a lone pair orbital of the water molecule is directed towards the cation while a hydrogen atom points towards the anion. In the five alkali halide solutions investigated ion pairing occurs only with CsF. The hydration numbers, when defined as the volume integrals of the ion-water radial pair correlation functions up to the first minimum, increase with increasing ion size and depend on the size of the counterion. The water-water interactions in the solutions show not only features of pure water at elevated temperatures but also of pure water under compresion. The agreement between calculated and measured self diffusion coefficients is still insufficient.

scholarly journals Computational Evidence Suggests That 1-chloroethanol May Be an Intermediate in the Thermal Decomposition of 2-chloroethanol into Acetaldehyde and HCl

2019 ◽  
Author(s):  
Zoi Salta ◽  
Agnie M. Kosmas ◽  
Oscar Ventura ◽  
Vincenzo Barone
Keyword(s):  
Aqueous Solution ◽  
Water Molecule ◽  
Gas Phase ◽  
Density Functional ◽  
Water Molecules ◽  
Functional Theory ◽  
Direct Transformation ◽  
The Density Functional Theory ◽  
Successive Step ◽  
The One

<p>The dehalogenation of 2-chloroethanol (2ClEtOH) in gas phase with and without participation of catalytic water molecules has been investigated using methods rooted into the density functional theory. The well-known HCl elimination leading to vinyl alcohol (VA) was compared to the alternative elimination route towards oxirane and shown to be kinetically and thermodynamically more favorable. However, the isomerization of VA to acetaldehyde in the gas phase, in the absence of water, was shown to be kinetically and thermodynamically less favorable than the recombination of VA and HCl to form the isomeric 1-chloroethanol (1ClEtOH) species. This species is more stable than 2ClEtOH by about 6 kcal mol<sup>-1</sup>, and the reaction barrier is 22 kcal mol<sup>-1</sup> vs 55 kcal mol<sup>-1</sup> for the direct transformation of VA to acetaldehyde. In a successive step, 1ClEtOH can decompose directly to acetaldehyde and HCl with a lower barrier (29 kcal mol<sup>-1</sup>) than that of VA to the same products (55 kcal mol<sup>-1</sup>). The calculations were repeated using a single ancillary water molecule (W) in the complexes 2ClEtOH_W and 1ClEtOH_W. The latter adduct is now more stable than 2ClEtOH_W by about 8 kcal mol<sup>-1</sup>, implying that the water molecule increased the already higher stability of 1ClEtOH in the gas phase. However, this catalytic water molecule lowers dramatically the barrier for the interconversion of VA to acetaldehyde (from 55 to 6 kcal mol<sup>-1</sup>). This barrier is now smaller than the one for the conversion to 1ClEtOH (which also decreases, but not so much, from 22 to 12 kcal mol<sup>-1</sup>). Thus, it is concluded that while 1ClEtOH may be a plausible intermediate in the gas phase dehalogenation of 2ClEtOH, it is unlikely that it plays a major role in water complexes (or, by inference, aqueous solution). It is also shown that neither in the gas phase nor in the cluster with one water molecule, the oxirane path is competitive with the VA alcohol path.</p>

Correlation Functions in the Isotropic Phase of Nematics

1984 ◽  
Vol 39 (6) ◽  
pp. 537-541
Author(s):  
E. Govers ◽  
G. Vertogen
Keyword(s):  
Free Energy ◽  
Energy Density ◽  
Correlation Functions ◽  
Free Energy Density ◽  
Isotropic Phase ◽  
Orientational Correlation ◽  
Orientational Correlation Functions

The orientational correlation functions in the isotropic phase of nematics are calculated starting from the expression of De Gennes for the free energy density of this phase.

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