A Molecular Dynamics Study of Aqueous Solutions II. Cesium Chloride in H2O

1975 ◽  
Vol 30 (6-7) ◽  
pp. 789-796 ◽  
Author(s):  
P. C. Vogel ◽  
K. Heinzinger
Keyword(s):  
Molecular Dynamics ◽  
Elevated Temperatures ◽  
Pure Water ◽  
Pair Correlation ◽  
Cesium Chloride ◽  
Pair Interaction ◽  
Chloride Ions ◽  
Water Molecules ◽  
Static Properties ◽  
Average Potential Energy

Abstract Results of a molecular dynamics study of an aqueous CsCl solution are reported. The system consisted of 216 particles, 200 water molecules, 8 cesium ions and 8 chloride ions and was run over 8000 time steps equivalent of 9 · 10-13 sec. On the basis of radial pair correlation functions, average potential energy of the water molecules and pair interaction energy distribution the static properties of the first hydration shells of the ions are discussed in detail. The self diffusion coefficient for the water molecules is calculated and compared with NMR measurement as well as with molecular dynamics calculations for pure water at elevated temperatures and pressures.

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.

A Molecular Dynamics Study of Aqueous Solutions I. First Results for LiCl in H2O

1974 ◽  
Vol 29 (8) ◽  
pp. 1164-1171 ◽  
Author(s):  
K. Heinzinger ◽  
P. C. Vogel
Keyword(s):  
Molecular Dynamics ◽  
Neutron Diffraction ◽  
Chloride Ions ◽  
Water Molecules ◽  
Kinetic Properties ◽  
Static Properties ◽  
Lithium Ions ◽  
X Ray ◽  
Hydration Shells ◽  
First Results

First results of a molecular dynamics study of an aqueous LiCl solution are reported. The system investigated consisted of 216 particles, 198 water molecules, 9 lithium ions, and 9 chloride ions. The calculations lead to fair agreement with the static properties of the first hydration shells of the ions as derived from X-ray and neutron diffraction studies, and with kinetic properties as derived from NMR measurements. A model for the motion of the water molecules in the first hydration sphere of Li+ is tentatively proposed.

scholarly journals Icephobicity of Functionalized Graphene Surfaces

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Xiang-Xiong Zhang ◽  
Min Chen
Keyword(s):  
Molecular Dynamics ◽  
Freezing Temperature ◽  
Ice Nucleation ◽  
Chloride Ions ◽  
Water Molecules ◽  
Sodium Ions ◽  
Functionalized Graphene ◽  
Functionalized Surfaces ◽  
The Difference ◽  
Dynamics Simulations

Manipulating the ice nucleation ability of liquid water by solid surface is of fundamental importance, especially in the design of icephobic surfaces. In this paper, the icephobicity of graphene surfaces functionalized by sodium ions, chloride ions, or methane molecules is investigated using molecular dynamics simulations. The icephobicity of the surface is evaluated by the freezing temperature. The freezing temperature on surface functionalized by methane molecules decreases at first and then increases as a function of the number groups, while the freezing temperature increases monotonically as a function of the number groups upon surfaces functionalized by sodium ions or chloride ions. The difference can be partially explained by the potential morphologies near the surfaces. Additionally, the validity of indicating the ice nucleation ability of water molecules using the number of six rings in the system is examined. Current study shows that the ice nucleation upon functionalized surfaces is inhibited when compared with smooth graphene substrate, which proves the feasibility of changing the icephobicity of the surfaces by functionalizing with certain ions or molecules.

MOLECULAR DYNAMICS SIMULATION ON THE STRUCTURE AND DYNAMICS OF WATER IN THE 1-BUTYL-3-METHYLIMIDAZOLIUM TETRAFLUOROBORATE/WATER MIXTURE

2010 ◽  
Vol 09 (03) ◽  
pp. 573-584 ◽  
Author(s):  
GUOCAI TIAN ◽  
JIAN LI
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Pure Water ◽  
Molar Fraction ◽  
Blue Shift ◽  
Dynamics Simulation ◽  
Water Molecules ◽  
Water Mixture ◽  
Structure And Dynamics ◽  
Hydrogen Bond Interactions

The micro-structure, and IR spectrum of water molecules in 1-butyl-3-methylimi- dazolium tetrafluoroborate( [Bmim]BF4 )/water mixture with different concentrations (x1 = 25.0%, 50.0%, 75.0%, and 90.0%) were studied with molecular dynamics simulation at room temperature. It was shown that water molecules tend to be isolated from each other in mixtures with more ions than water molecules in pure water. With the increase of the molar fraction of water in the mixture, the rotation bands and the bending bands of water display red shift from 566.2 to 651.4 cm-1 and from 1638.4 to 1683.2 cm-1 respectively, whereas the O–H stretch bands show blue shift from 3519.8 to 3452 cm-1, which agree well with the experimental results. This suggests that the molecules are hindered and their motions are difficult and slow, due to the hydrogen-bond interactions and the inharmonic interactions between the inter- or intra-molecular modes of water molecules.

A Molecular Dynamics Study of Aqueous Solutions

1976 ◽  
Vol 31 (5) ◽  
pp. 476-481 ◽  
Author(s):  
P. C. Vogel ◽  
K. Heinzinger
Keyword(s):  
Molecular Dynamics ◽  
Aqueous Solutions ◽  
Internal Pressure ◽  
Chloride Ions ◽  
Water Molecules ◽  
Sodium Ions ◽  
Nacl Solution ◽  
Hydration Shells

Abstract Results of a molecular dynamics study of a 0.55 molal aqueous NaCl solution are reported. The basic periodic box contained 200 water molecules, 2 sodium ions and 2 chloride ions. The calculated properties of this solution are compared with those obtained previously for a 2.2 molal NaCl solution. The formation of second hydration shells, an increase of the number of water molecules in the first hydration shells, and a release of internal pressure are the main changes connected with a decrease of the concentration.

A Molecular Dynamics Study of Aqueous Solutions. VII. Improved Simulation and Comparison with X-Ray Investigations of a NaCl Solution

1977 ◽  
Vol 32 (10) ◽  
pp. 1137-1145 ◽  
Author(s):  
G. Pálinkás ◽  
W. O. Riede ◽  
K. Heinzinger
Keyword(s):  
Molecular Dynamics ◽  
Structure Function ◽  
Correlation Functions ◽  
Pair Correlation ◽  
Chloride Ions ◽  
Dynamics Simulation ◽  
Nacl Solution ◽  
Ewald Summation ◽  
Pair Correlation Functions ◽  
X Ray

The molecular dynamics simulation has been improved by introducing the Ewald summation for ion-ion interactions. On the basis of the Pauling radii new Lennard-Jones parameters have been derived for the halide ions. The results of a simulation of a system consisting of 200 water molecules, 8 sodium and 8 chloride ions are compared with x-ray investigations of a 2 molal NaCl solution through the structure functions. The first neighbor model commonly used in the x-ray analysis of multicomponent liquids is fitted to the experimental structure function and to the structure function calculated from the radial pair correlation functions of the simulation. The parameters of the two fits and the radial pair correlation functions calculated from the fitted first neighbor model are compared. On the basis of this comparison the usefulness and the limitations of the first neighbor model are discussed

scholarly journals Mechanism of dehydration in a non-porous variable hydrate

2014 ◽  
Vol 70 (a1) ◽  
pp. C1000-C1000
Author(s):  
Laszlo Fabian
Keyword(s):  
Molecular Dynamics ◽  
Conformational Changes ◽  
Chloride Ions ◽  
Smooth Transition ◽  
Water Molecules ◽  
Present Contribution ◽  
Gated Channel ◽  
Mechanism Of Dehydration ◽  
Paroxetine Hydrochloride ◽  
Dynamics Simulations

Paroxetine hydrochloride form II (PHCl-II) is a variable hydrate with a peculiar behaviour [1]. It changes its water content in response to changes in relative humidity with remarkable speed and in a completely reversible fashion. This is commonly observed for channel hydrates, but no continuous channels exist in the PHCl-II structure [2]. Powder diffraction results showed that loss of water produces an isostructural anhydrate, suggesting a simple, non-destructive mechanism of dehydration. The aim of the present contribution is to explain this unusual behaviour at a molecular level by using molecular dynamics simulations. Models of both the hydrated and anhydrous state could be created from the experimental hydrate structure by simple energy minimisation, which is in accordance with the experimentally observed smooth transition. A partially dehydrated supercell model was used to study the mechanism which allows water molecules to cross the steric barrier between adjacent solvent cavities. Since such transitions are rare on the simulation timescale (µs to ms), a steered molecular dynamics approach was applied. The results show that the passage of water molecules is facilitated by conformational changes, in which a ring system acts as a gate between cavities. When passing through the 'gate', water molecules are relayed between two chloride ions: as one Cl...HOH hydrogen bond is broken, another HOH...Cl one is formed. The progress of water molecules along the gated channel is not continuous, they spend a significant amount of time in each cavity between consecutive passages.

Long-range Structures in Bulk Water. A Molecular Dynamics Study

1997 ◽  
Vol 52 (5) ◽  
pp. 432-434 ◽  
Author(s):  
Axel Kohlmeyer ◽  
Wolfgang Witschel ◽  
Eckhard Spohr
Keyword(s):  
Molecular Dynamics ◽  
Correlation Functions ◽  
Pair Correlation ◽  
Bulk Water ◽  
Water Molecules ◽  
Partial Structure ◽  
Pair Correlation Functions ◽  
Large Bulk ◽  
Structure Factors ◽  
Dynamics Simulations

Abstract We present recent calculations of pair correlation functions and partial structure factors derived from molecular dynamics simulations of large bulk water systems (up to 12 167 water molecules). We observe small amplitude oscillations of the pair correlation functions in the range between 10 and 20 Ä.

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