Adjustable diffusion enhancement of water molecules in a nanoscale water bridge

In this paper we report on dynamical properties of a 2.2 molal aqueous KCl solution as obtained from an 8.7 ps MD simulation at an average temperature of 289 K. Velocity autocorrelation functions, self-diffusion coefficients and spectral densities of the hindered translational and librational motions of the ions and the water molecules assigned to three subsystems - hydration water of the cations, hydration water of the anions and bulk water - are discussed.

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Effect of Modification on the Fluid Diffusion Coefficient in Silica Nanochannels

Molecules ◽

10.3390/molecules26134030 ◽

2021 ◽

Vol 26 (13) ◽

pp. 4030

Author(s):

Gengbiao Chen ◽

Zhiwen Liu

Keyword(s):

Diffusion Coefficient ◽

Diffusion Coefficients ◽

Surface Effect ◽

Bulk Water ◽

Self Diffusion ◽

Average Diffusion Coefficient ◽

Average Diffusion ◽

Chain Lengths ◽

Fluid Diffusion ◽

Self Diffusion Coefficient

The diffusion behavior of fluid water in nanochannels with hydroxylation of silica gel and silanization of different modified chain lengths was simulated by the equilibrium molecular dynamics method. The diffusion coefficient of fluid water was calculated by the Einstein method and the Green–Kubo method, so as to analyze the change rule between the modification degree of nanochannels and the diffusion coefficient of fluid water. The results showed that the diffusion coefficient of fluid water increased with the length of the modified chain. The average diffusion coefficient of fluid water in the hydroxylated nanochannels was 8.01% of the bulk water diffusion coefficient, and the diffusion coefficients of fluid water in the –(CH2)3CH3, –(CH2)7CH3, and –(CH2)11CH3 nanochannels were 44.10%, 49.72%, and 53.80% of the diffusion coefficients of bulk water, respectively. In the above four wall characteristic models, the diffusion coefficients in the z direction were smaller than those in the other directions. However, with an increase in the silylation degree, the increased self-diffusion coefficient due to the surface effect could basically offset the decreased self-diffusion coefficient owing to the scale effect. In the four nanochannels, when the local diffusion coefficient of fluid water was in the range of 8 Å close to the wall, Dz was greater than Dxy, and beyond the range of 8 Å of the wall, the Dz was smaller than Dxy.

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Effect of Energy and Dose on Transient-Enhanced Diffusion and Defect Microstructure in Low Energy High Dose As+ Implanted Si

MRS Proceedings ◽

10.1557/proc-438-21 ◽

1996 ◽

Vol 438 ◽

Author(s):

V. Krishnamoorthy ◽

D. Venables ◽

K. Moeller ◽

K. S. Jones ◽

B. Freer

Keyword(s):

Point Defects ◽

Surface Recombination ◽

High Dose ◽

Enhanced Diffusion ◽

Projected Range ◽

Diffusion Enhancement ◽

Defect Microstructures ◽

Dose Dependent ◽

Higher Doses ◽

Defect Microstructure

Abstract(001) CZ silicon wafers were implanted with arsenic (As+) at energies of 10–50keV to doses of 2×1014 to 5×1015/cm2. All implants were amorphizing in nature. The samples were annealed at 700°C for 16hrs. The resultant defect microstructures were analyzed by XTEM and PTEM and the As profiles were analyzed by SIMS. The As profiles showed significantly enhanced diffusion in all of the annealed specimens. The diffusion enhancement was both energy and dose dependent. The lowest dose implant/annealed samples did not show As clustering which translated to a lack of defects at the projected range. At higher doses, however, projected range defects were clearly observed, presumably due to interstitials generated during As clustering. The extent of enhancement in diffusion and its relation to the defect microstructure is explained by a combination of factors including surface recombination of point defects, As precipitation, As clustering and end of range damage.

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Ein Wasserstoffisotopieeffekt im CuSO4 * 5H2O

Zeitschrift für Naturforschung A ◽

10.1515/zna-1969-1007 ◽

1969 ◽

Vol 24 (10) ◽

pp. 1502-1511

Author(s):

Karl Heinzinger

Keyword(s):

Water Vapor ◽

Aqueous Solutions ◽

Separation Factor ◽

Room Temperature ◽

Copper Ion ◽

Hydrogen Isotopes ◽

Bulk Water ◽

Water Molecules ◽

Hydration Water ◽

Sulfate Solutions

Abstract There are two kinds of water in CuSO4·5H2O differing by their binding in the crystal. The oxygen of four water molecules is bonded to the copper ion, that of the fifth molecule is hydrogen bonded. It is shown that the D/H ratios of these two kinds of water differ by 5.7%, the light isotope being enriched in the water molecules coordinated with the copper ion. The results show that there is no exchange of the hydrogen isotopes during the time needed for dehydration at room temperature which takes several days. The assumption has been confirmed that the water coordinated with the copper ion leaves the crystal first on dehydration at temperatures below 50 °C. Additional measurements of the separation factor for the hydrogen isotopes between water vapor and copper sulfate solutions allow conclusions on the fractionation of the hydrogen isotopes between bulk water and hydration water in aqueous solutions.

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Proton Transfer in Bulk Water using the Full Adaptive QM/MM Method: Integration of Solute- and Solvent-Adaptive Approaches

10.26434/chemrxiv.12638285 ◽

2020 ◽

Author(s):

Hiroshi C. Watanabe ◽

Masayuki Yamada ◽

Yohichi Suzuki

Keyword(s):

Proton Transfer ◽

Control Algorithm ◽

Adaptive Methods ◽

Bulk Water ◽

Water Molecules ◽

Adaptive Treatment ◽

Grotthuss Mechanism ◽

Hydronium Ions ◽

Method Integration ◽

Large Systems

<div><div>The quantum mechanical/molecular mechanical (QM/MM) method is a hybrid molecular simulation technique that increases the accessibility of local electronic structures of large systems.</div><div> The technique combines the benefit of accuracy found in the QM method and that of cost efficiency found in the MM method.</div><div> However, it is difficult to directly apply the QM/MM method to the dynamics of solution systems, particularly for proton transfer. </div><div> As explained in the Grotthuss mechanism, proton transfer is a structural interconversion between hydronium ions and solvent water molecules. </div><div> Hence, when the QM/MM method is applied, an adaptive treatment, namely on-the-fly revisions on molecular definitions, is required for both the solute and solvent. </div><div> Although several solvent-adaptive methods have been proposed, a full adaptive framework, which is an approach that also considers adaptation for solutes, remains untapped. In this paper, we propose a new numerical expression for the coordinates of the excess proton and its control algorithm.</div><div> Furthermore, we confirm that this method can stably and accurately simulate proton transfer dynamics in bulk water.</div></div>

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c , T-Dependence of the Self Diffusion in Concentrated Aqueous Sucrose Solutions

Zeitschrift für Naturforschung C ◽

10.1515/znc-1994-3-415 ◽

1994 ◽

Vol 49 (3-4) ◽

pp. 258-264 ◽

Cited By ~ 15

Author(s):

D. Girlich ◽

H.-D. Lüdemann ◽

C. Buttersack ◽

K. Buchholz

Keyword(s):

Field Gradient ◽

Concentration Dependence ◽

Diffusion Coefficients ◽

The Self ◽

Water Molecules ◽

Pulsed Field Gradient Nmr ◽

Pulsed Field ◽

Self Diffusion ◽

Sucrose Solutions ◽

Wide Range

The self diffusion coefficients D of the water molecules and of sucrose have been determined by the pulsed field gradient NMR technique over a wide range of temperatures and concentrations (cmax: 70% w/w suc.). All temperature dependencies can be fitted to a Vogel- Tammann-Fulcher equation. The isothermic concentration dependence of D for the sucrose is given by a simple exponential concentration dependence

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Adsorption and mobility of water molecules and organic substances in carbon adsorbents Communication 3. Dependence of self-diffusion coefficients of adsorbed molecules of water and methanol on size of micropores in active carbons and on degree of pore filling

Bulletin of the Academy of Sciences of the USSR Division of Chemical Science ◽

10.1007/bf01557497 ◽

1987 ◽

Vol 36 (7) ◽

pp. 1346-1350

Author(s):

P. Walter ◽

R. Sh. Vartapetyan ◽

A. M. Voloshchuk ◽

M. M. Dubinin ◽

J. Kärger ◽

...

Keyword(s):

Diffusion Coefficients ◽

Carbon Adsorbents ◽

Water Molecules ◽

Organic Substances ◽

Active Carbons ◽

Pore Filling ◽

Adsorbed Molecules ◽

Self Diffusion

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Enhanced Diffusion in a Model of Molecular Motors with Potential Switching

Fluctuation and Noise Letters ◽

10.1142/s0219477519400054 ◽

2019 ◽

Vol 18 (02) ◽

pp. 1940005 ◽

Cited By ~ 1

Author(s):

Ryota Shinagawa ◽

Kazuo Sasaki

Keyword(s):

Diffusion Coefficient ◽

External Force ◽

Molecular Motors ◽

Periodic Potential ◽

Brownian Particle ◽

Molecular Motor ◽

Free Diffusion ◽

Enhanced Diffusion ◽

Additional Peak ◽

Diffusion Enhancement

Diffusion enhancement is a phenomenon in which the diffusion coefficient of a system is increased by an external force and it becomes larger than that of the force-free diffusion in thermal equilibrium. It is known that this phenomenon occurs for a Brownian particle in a periodic potential under a constant external force. Recently, it was found that diffusion enhancement also occurred in a biological molecular motor, whose moving part could move itself by switching the potentials generated by the other parts. It was shown that the diffusion coefficient exhibited peaks as a function of a constant external force. Here, we report the occurrence of an additional peak and investigate the condition governing its appearance.

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Thrombin-thrombomodulin interaction: energetics and potential role of water as an allosteric effector

Biochemical Journal ◽

10.1042/bj3100049 ◽

1995 ◽

Vol 310 (1) ◽

pp. 49-53 ◽

Cited By ~ 3

Author(s):

R De Cristofaro ◽

M Picozzi ◽

E De Candia ◽

B Rocca ◽

R Landolfi

Keyword(s):

Conformational Changes ◽

Potential Role ◽

Competitive Inhibition ◽

Entropy Change ◽

Bulk Water ◽

Water Molecules ◽

Rabbit Lung ◽

Allosteric Effector ◽

Free Energy Of Binding

The interaction of rabbit lung thrombomodulin (TM) and C-terminal hirudin 54-65 fragment (Hir54-65) with human alpha-thrombin were investigated by exploiting their competitive inhibition of thrombin-fibrinogen interaction. Measurements of Ki values for TM and Hir54-65 interactions with human alpha-thrombin performed over a temperature range spanning from 10 to 40 degrees C showed a constant enthalpy for both ligands. The enthalpic and entropic contributions to the free energy of binding, however, are different for TM and the hirudin peptide. The calculated values of delta H and delta S, in fact, were -47.3 +/- 2.51 kJ (-11.3 +/- 0.6 kcal)/mol and -42.7 +/- 7.9 J (-10.2 +/- 1.9 cal)/mol.K for the hirudin peptide, while being -22.9 +/- 2.09 kJ (-5.47 +/- 0.5 kcal)/mol and 102.50 +/- 6.69 J (24.5 +/- 1.6 cal)/mol.K respectively for TM binding. These findings indicate that the interaction between thrombin and Hir54-65 is largely driven by the enthalpic contribution, whereas the positive entropy change is the driving force for the formation of the thrombin-TM complex. In other experiments performed in the presence of various concentrations of either sorbitol or sucrose it could be demonstrated that the value of the equilibrium association constant for thrombin-TM interaction increases as a function of the osmotic pressure, while the thrombin-Hir54-65 interaction was not affected by the same conditions. Moreover, control experiments showed that no major conformational changes are produced on TM by osmotic pressures used in the present study. From these experiments it was calculated that roughly 35 water molecules are released into the bulk water upon TM binding. Such a phenomenon, which is likely to be responsible for the entropic change described above, indicates the relevance of hydration processes for the formation of the thrombin-TM adduct.

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Effect of Energy and Dose on Transient-Enhanced Diffusion and Defect Microstructure in Low Energy High Dose As+ Implanted Si

MRS Proceedings ◽

10.1557/proc-439-29 ◽

1996 ◽

Vol 439 ◽

Author(s):

V. Krishnamoorthy ◽

D. Venables ◽

K. Moeller ◽

K. S. Jones ◽

B. Freer

Keyword(s):

Point Defects ◽

Surface Recombination ◽

High Dose ◽

Enhanced Diffusion ◽

Projected Range ◽

Diffusion Enhancement ◽

Defect Microstructures ◽

Dose Dependent ◽

Higher Doses ◽

Defect Microstructure

Abstract(001) CZ silicon wafers were implanted with arsenic (As+) at energies of 10–50keV to doses of 2x 1014 to 5x1015/cm2. All implants were amorphizing in nature. The samples were annealed at 700°C for 16hrs. The resultant defect microstructures were analyzed by XTEM and PTEM and the As profiles were analyzed by SIMS. The As profiles showed significantly enhanced diffusion in all of the annealed specimens. The diffusion enhancement was both energy and dose dependent. The lowest dose implant/annealed samples did not show As clustering which translated to a lack of defects at the projected range. At higher doses, however, projected range defects were clearly observed, presumably due to interstitials generated during As clustering. The extent of enhancement in diffusion and its relation to the defect microstructure is explained by a combination of factors including surface recombination of point defects, As precipitation, As clustering and end of range damage.

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