scholarly journals Orientational ordering of water in extended hydration shells of cations is ion-specific and is correlated directly with viscosity and hydration free energy

2017 ◽  
Vol 19 (36) ◽  
pp. 24678-24688 ◽  
Author(s):  
Yixing Chen ◽  
Halil I. Okur ◽  
Chungwen Liang ◽  
Sylvie Roke
Keyword(s):  
Free Energy ◽  
Aqueous Solutions ◽  
Hydration Free Energy ◽  
Specific Ion Effects ◽  
Hydration Shells ◽  
Orientational Ordering ◽  
Ion Effects

Specific ion effects in aqueous solutions are investigated at the molecular, nanoscopic and macroscopic levels.

Specific Ion Effects of Azobenzene Salts on Photoresponse of PNIPAm in Aqueous Solutions

2021 ◽  
pp. 2100232
Author(s):  
Shuang Wei ◽  
Zechuan Zhang ◽  
Weibin Dong ◽  
Ting Liang ◽  
Junyi Ji ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Specific Ion Effects ◽  
Ion Effects

Specific Ion Effects on Hydrogen-Bond Rearrangements in the Halide–Dihydrate Complexes

2019 ◽  
Author(s):  
Pushp Bajaj ◽  
Debbie Zhuang ◽  
Francesco Paesani
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Quantum Molecular Dynamics ◽  
Ion Hydration ◽  
Systematic Analysis ◽  
Bonding Structure ◽  
Specific Ion Effects ◽  
Hydration Shells ◽  
Ion Effects ◽  
Water Hydrogen

<div> <div> <div> <p>Small aqueous ionic clusters represent ideal systems to investigate the microscopic hydrogen-bonding structure and dynamics in ion hydration shells. In this context, halide-dihydrate complexes are the smallest systems where the interplay between halide–water and water–water interactions can be studied simultaneously. Here, quantum molecular dynamics simulations unravel specific ion effects on the temperature-dependent structural transition in X<sup>-</sup>(H<sub>2</sub>O)<sub>2</sub> complexes (X = Cl, Br and I) which is induced by the breaking of the water–water hydrogen bond. A systematic analysis of the hydrogen-bonding rearrangements at low temperature provides fundamental insights into the competition between halide–water and water–water interactions depending on the properties of the halide ion. While the halide–water hydrogen-bond strength decreases going from Cl<sup>-</sup>(H<sub>2</sub>O)<sub>2</sub> to I<sup>-</sup>(H<sub>2</sub>O)<sub>2</sub>, the opposite trend in observed in the strength of the water–water hydrogen-bond, suggesting that non-trivial many-body effects may also be at play in the hydration shells of halide ions in solution, especially in frustrated systems (e.g., interfaces) where the water molecules can have dangling OH bonds.</p> </div> </div> </div>

scholarly journals A Molecular Dynamics Approach to Calculate the Thermodiffusion (Soret and Seebeck) Coefficients of Salts in Aqueous Solutions

2021 ◽  
Author(s):  
Leandro Rezende Franco ◽  
André Luiz Sehnem ◽  
Antônio Martins Figueiredo Neto ◽  
Kaline Coutinho
Keyword(s):  
Molecular Dynamics ◽  
Free Energy ◽  
Aqueous Solutions ◽  
Optical Measurements ◽  
Soret Coefficient ◽  
System Response ◽  
Physical Parameters ◽  
Hydration Free Energy ◽  
Self Diffusion ◽  
Seebeck Coefficients

<div><div><div><p>An approach to investigate the physical parameters related to the ions thermodiffusion in aqueous solution is proposed herein by calculating the equilibrium hydration free energy and the self-diffusion coefficient as a function of temperature, ranging from 293 to 353 K, using molecular dynamics simulations of infinitely diluted ions in aqueous solutions. Several ion force field parameters are used in the simulations and new parameters are proposed for some ions to better describe their hydration free energy. Such a theoretical framework enables the calculation of some single-ion properties, such as heat of transport, Soret coefficient and mass current density, as well as properties of salts, such as effective mass and thermal diffusion, Soret and Seebeck coefficients. These calculated properties are compared with experimental data available from optical measurements and showed good agreement revealing an excellent theoretical predictability of salt thermodiffusion properties. Differences in single-ion Soret and self-diffusion coefficients of anions and cations give rise to a thermoelectric field, which affects the system response that is quantified by the Seebeck coefficient. The fast and slow Seebeck coefficients are calculated and discussed, resulting in values with mV/K order-of-magnitude, as observed in experiments involving several salts, such as K+Cl−, Na+Cl−, H+Cl−, Na+OH−, TMA+OH− and TBA+OH−. The present approach can be adopted for any ion or charged particle dispersed in water with the aim of predicting the thermoelectric field induced through the fluid. It has potential applications in designing electrolytes for ionic thermoelectric devices in order to harvest energy and thermoelectricity in biological nanofluids.</p></div></div></div>

Specific Ion Effects on Hydrogen-Bond Rearrangements in the Halide–Dihydrate Complexes

2019 ◽  
Author(s):  
Pushp Bajaj ◽  
Debbie Zhuang ◽  
Francesco Paesani
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Quantum Molecular Dynamics ◽  
Ion Hydration ◽  
Systematic Analysis ◽  
Bonding Structure ◽  
Specific Ion Effects ◽  
Hydration Shells ◽  
Ion Effects ◽  
Water Hydrogen

<div> <div> <div> <p>Small aqueous ionic clusters represent ideal systems to investigate the microscopic hydrogen-bonding structure and dynamics in ion hydration shells. In this context, halide-dihydrate complexes are the smallest systems where the interplay between halide–water and water–water interactions can be studied simultaneously. Here, quantum molecular dynamics simulations unravel specific ion effects on the temperature-dependent structural transition in X<sup>-</sup>(H<sub>2</sub>O)<sub>2</sub> complexes (X = Cl, Br and I) which is induced by the breaking of the water–water hydrogen bond. A systematic analysis of the hydrogen-bonding rearrangements at low temperature provides fundamental insights into the competition between halide–water and water–water interactions depending on the properties of the halide ion. While the halide–water hydrogen-bond strength decreases going from Cl<sup>-</sup>(H<sub>2</sub>O)<sub>2</sub> to I<sup>-</sup>(H<sub>2</sub>O)<sub>2</sub>, the opposite trend in observed in the strength of the water–water hydrogen-bond, suggesting that non-trivial many-body effects may also be at play in the hydration shells of halide ions in solution, especially in frustrated systems (e.g., interfaces) where the water molecules can have dangling OH bonds.</p> </div> </div> </div>

scholarly journals A Molecular Dynamics Approach to Calculate the Thermodiffusion (Soret and Seebeck) Coefficients of Salts in Aqueous Solutions

2021 ◽  
Author(s):  
Leandro Rezende Franco ◽  
André Luiz Sehnem ◽  
Antônio Martins Figueiredo Neto ◽  
Kaline Coutinho
Keyword(s):  
Molecular Dynamics ◽  
Free Energy ◽  
Aqueous Solutions ◽  
Optical Measurements ◽  
Soret Coefficient ◽  
System Response ◽  
Physical Parameters ◽  
Hydration Free Energy ◽  
Self Diffusion ◽  
Seebeck Coefficients

<div><div><div><p>An approach to investigate the physical parameters related to the ions thermodiffusion in aqueous solution is proposed herein by calculating the equilibrium hydration free energy and the self-diffusion coefficient as a function of temperature, ranging from 293 to 353 K, using molecular dynamics simulations of infinitely diluted ions in aqueous solutions. Several ion force field parameters are used in the simulations and new parameters are proposed for some ions to better describe their hydration free energy. Such a theoretical framework enables the calculation of some single-ion properties, such as heat of transport, Soret coefficient and mass current density, as well as properties of salts, such as effective mass and thermal diffusion, Soret and Seebeck coefficients. These calculated properties are compared with experimental data available from optical measurements and showed good agreement revealing an excellent theoretical predictability of salt thermodiffusion properties. Differences in single-ion Soret and self-diffusion coefficients of anions and cations give rise to a thermoelectric field, which affects the system response that is quantified by the Seebeck coefficient. The fast and slow Seebeck coefficients are calculated and discussed, resulting in values with mV/K order-of-magnitude, as observed in experiments involving several salts, such as K+Cl−, Na+Cl−, H+Cl−, Na+OH−, TMA+OH− and TBA+OH−. The present approach can be adopted for any ion or charged particle dispersed in water with the aim of predicting the thermoelectric field induced through the fluid. It has potential applications in designing electrolytes for ionic thermoelectric devices in order to harvest energy and thermoelectricity in biological nanofluids.</p></div></div></div>

Can the anomalous aqueous solubility of β-cyclodextrin be explained by its hydration free energy alone?

2008 ◽  
Vol 10 (22) ◽  
pp. 3236 ◽  
Author(s):  
Wensheng Cai ◽  
Tingting Sun ◽  
Xueguang Shao ◽  
Christophe Chipot
Keyword(s):  
Free Energy ◽  
Aqueous Solubility ◽  
Hydration Free Energy
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