Modelling of interactions in solutions: alkali halides in DMSO

1979 ◽  
Vol 57 (5) ◽  
pp. 538-551 ◽  
Author(s):  
Peeter Kruus ◽  
Barbara E. Poppe
Keyword(s):  
Reasonable Agreement ◽  
Minimum Energy ◽  
Alkali Halides ◽  
Ion Pair ◽  
Point Of View ◽  
Ion Solvation ◽  
Solvation Energies ◽  
Solvent Molecules ◽  
A Charge ◽  
Energy Configurations

A model of solutions of alkali halides in DMSO is developed. Each ion is described by a radius, a charge, a polarizability, and an exponential repulsion parameter. Each molecule is described by a polarizability, charges, 6-12 energy parameters, and 6-12 distance parameters centered on each of the 10 atoms in the molecule. The model is applied to calculate (i) the vaporization energy of solvent molecules, (ii) single ion solvation energies and configurations of the solvating molecules, and (iii) the energy as a function of reaction coordinate for the formation of an ion pair. The energies and configurations are obtained by allowing the systems to relax to minimum energy configurations by allowing motion of the molecules. The results of (i) give a vaporization energy 60% of the experimental. The results of (ii) give solvation energies in reasonable agreement with the experimental, and configurations which are reasonable from the point of view of mobilities of ions. The results of (iii) show the presence of a distinct solvent separated ion pair which actually has an energy lower than the contact ion pair. Advantages and problems involved in using this approach to model solutions are discussed.

Ion Pair Formation and Solvation Energies in Solutions of Alkali Halides in Dimethyl Sulfoxide. II. Model Calculations

1975 ◽  
Vol 53 (7) ◽  
pp. 1007-1018 ◽  
Author(s):  
Merrill S. Goldenberg ◽  
Peeter Kruus ◽  
Stephen K. F. Luk
Keyword(s):  
Dimethyl Sulfoxide ◽  
Electrostatic Interactions ◽  
Minimum Energy ◽  
Alkali Halides ◽  
Dmso Molecule ◽  
Ion Pair ◽  
Model Calculations ◽  
Energy Calculations ◽  
Solvation Energies ◽  
Repulsive Forces

Energy calculations were carried out on models of molecular-level structures likely to be present in solutions of alkali halides in dimethyl sulfoxide (DMSO). Classical electrostatic interactions were assumed, and polarization of a DMSO molecule was assumed due to the fields of the ions only. The validity of this assumption was tested. DMSO molecules were represented by increasingly detailed models, with most calculations carried out with each molecule represented by 10 point charges and 9 polarizable bonds. A program including up to 14 such molecules and two ions was used for energy and distance calculations, and is made available. Polarization effects are as important as interactions between permanent charges for energy calculations. The configurations of minimum energy determined by classical electrostatics often do not involve overlap of the "hard-sphere radii" of neighboring species, so that the neglect of quantum mechanical repulsive forces seems justified. Energy cycles using the calculated energies for ion–solvent complexes predicted experimental cation enthalpies with some success. The form of the potential for vibration of a cation in a solvent shell was investigated and found in cases not to have an energy minimum at the shell center. Calculations including next-nearest solvating DMSO's indicate a rather loose structure. An energy profile for an anion moving from a solvent-separated ion pair position to a contact-ion pair position is presented.

Ion solvation by dipolar aprotic solvents. An ab initio study

1987 ◽  
Vol 52 (1) ◽  
pp. 6-13 ◽  
Author(s):  
Petr Kyselka ◽  
Zdeněk Havlas ◽  
Ivo Sláma
Keyword(s):  
Ab Initio ◽  
Geometry Optimization ◽  
Molecular Structures ◽  
Dimethyl Sulphoxide ◽  
Ion Solvation ◽  
Interaction Energies ◽  
Ab Initio Study ◽  
Solvation Energies ◽  
Dipolar Aprotic Solvents ◽  
Complete Geometry Optimization

The paper deals with the solvation of Li+, Be2+, Na+, Mg2+, and Al3+ ions in dimethyl sulphoxide, dimethylformamide, acetonitrile, and water. The ab initio quantum chemical method was used to calculate the solvation energies, molecular structures, and charge distributions for the complexes water···ion, acetonitrile···ion, dimethyl sulphoxide···ion, and dimethylformamide···ion. The interaction energies were corrected for the superposition error. Complete geometry optimization was performed for the complex water···ion. Some generalizations are made on the basis of the results obtained.

Optimization of Wind Turbines Using Helicoidal Vortex Model

2003 ◽  
Author(s):  
Jean-Jacques Chattot
Keyword(s):  
Minimum Energy ◽  
Energy Condition ◽  
Integral Relation ◽  
Point Of View ◽  
Maximum Output ◽  
Efficient Design ◽  
Profile Data ◽  
Vortex Model ◽  
Viscous Profile ◽  
Optimum Solution

The problem of the design of a wind turbine for maximum output is addressed from an aerodynamical point of view. It is shown that the optimum inviscid design, based on the Goldstein model, satifies the minimum energy condition of Betz only for light loading. The more general equation governing the optimum is derived and an integral relation is obtained, stating that the optimum solution satisfies the minimum energy condition of Betz in the Trefftz plane “in the average”. The discretization of the problem is detailed, including the viscous correction based on the 2-D viscous profile data. A constraint is added to account for the force on the tower. The minimization problem is solved very efficiently by relaxation. Several optimized solutions are calculated and compared with the NREL rotor, using the same profile, but different chord and twist distributions. In all cases, the optimization produces a more efficient design.

SUBSTITUTION AT OCTAHEDRAL CENTERS: II. EFFECT OF SALTS UPON THE RATE OF HYDROLYSIS OF THE HALOPENTAMMINECHROMIUM(III) IONS

1961 ◽  
Vol 39 (11) ◽  
pp. 2371-2379 ◽  
Author(s):  
T. P. Jones ◽  
W. E. Harris ◽  
W. J. Wallace
Keyword(s):  
Charge Transfer ◽  
Transfer Effect ◽  
Ion Pair ◽  
Pair Formation ◽  
Sodium Salts ◽  
Rate Acceleration ◽  
Rate Of Hydrolysis ◽  
A Charge ◽  
Hydrolysis Of ◽  
Octahedral Configuration

A study of the hydrolysis of the halopentamminechromium(III) ions in the presence of the sodium salts of weak acids reveals a rate acceleration due to specific ion-pair formation. The acceleration is due partly to a charge-transfer effect and partly to the fact that the ion helps to maintain the octahedral configuration of the complex in the transition state. It is concluded that the reaction occurs by dissociation, but without collapse of the structure to a five-co-ordinated intermediate.

scholarly journals Clusters, columns, and lamellae—minimum energy configurations in core softened potentials

Soft Matter ◽  
2008 ◽  
Vol 4 (7) ◽  
pp. 1396 ◽  
Author(s):  
Gernot J. Pauschenwein ◽  
Gerhard Kahl
Keyword(s):  
Minimum Energy ◽  
Energy Configurations

Minimum energy configurations

Nature ◽  
1986 ◽  
Vol 319 (6053) ◽  
pp. 454-454 ◽  
Author(s):  
M.G. CALKIN ◽  
D. KIANG ◽  
D.A. TINDALL
Keyword(s):  
Minimum Energy ◽  
Energy Configurations

Gas-phase electrochemistry: Measuring absolute potentials and investigating ion and electron hydration

2011 ◽  
Vol 83 (12) ◽  
pp. 2129-2151 ◽  
Author(s):  
William A. Donald ◽  
Evan R. Williams
Keyword(s):  
Gas Phase ◽  
Ion Solvation ◽  
Water Molecules ◽  
Hydrogen Electrode ◽  
Half Cell ◽  
Hydration Enthalpy ◽  
A Value ◽  
Hydrated Ions ◽  
Solvation Energies ◽  
The University

In solution, half-cell potentials and ion solvation energies (or enthalpies) are measured relative to other values, thus establishing ladders of thermochemical values that are referenced to the potential of the standard hydrogen electrode (SHE) and the proton hydration energy (or enthalpy), respectively, which are both arbitrarily assigned a value of 0. In this focused review article, we describe three routes for obtaining absolute solution-phase half-cell potentials using ion nanocalorimetry, in which the energy resulting from electron capture (EC) by large hydrated ions in the gas phase are obtained from the number of water molecules lost from the reduced precursor cluster, which was developed by the Williams group at the University of California, Berkeley. Recent ion nanocalorimetry methods for investigating ion and electron hydration and for obtaining the absolute hydration enthalpy of the electron are discussed. From these methods, an absolute electrochemical scale and ion solvation scale can be established from experimental measurements without any models.

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