scholarly journals #ECS236, Tuesday, 15 October 2019, 08:30 - 09:10, Room 209, Molecular Dynamics Analysis on the Behavior of Water and Alcohol Liquids on a OH-Terminated SiO2 Surface

2019 ◽  
Author(s):  
Yasutaka Yamaguchi
Keyword(s):  
Molecular Dynamics ◽  
Solid Surface ◽  
Adsorption Layer ◽  
Md Simulations ◽  
Hydroxyl Groups ◽  
Sio2 Surface ◽  
Surface Hydroxyl ◽  
Wet Process ◽  
Water Solvent ◽  
State Water

In this study, we carried molecular dynamics (MD) simulations of water and various alcohol liquids on a flat SiO2 surface terminated by hydroxyl groups in order to examine the microscopic structures of these liquids near the solid surface and diffusion property for the fundamental understanding of the wet process during the semiconductor fabrication. As an equilibrium state, water as well as methanol, ethanol and isopropyl alcohol (IPA) molecules formed a multiple layered structure on the solid surface; however, the microscopic structures were remarkably different between water and IPA liquids because the IPA molecules in the first adsorption layer strongly adsorbed on the solid surface through the hydrogen bond with the surface hydroxyl groups with directing hydrophobic CH3 groups toward the second layer. Non-equilibrium MD simulations of the dilution of water/IPA adsorption layer by IPA/water solvent revealed that the strongly adsorbed IPA layer can easily be replaced by water molecules.

A computational study of the adsorption of the isomers of butanol on silicalite and H-ZSM-5

1994 ◽  
Vol 446 (1928) ◽  
pp. 411-427 ◽  
Keyword(s):  
Molecular Dynamics ◽  
Monte Carlo ◽  
Energy Minimization ◽  
Computational Study ◽  
Hydroxyl Groups ◽  
Confinement Effects ◽  
Surface Hydroxyl ◽  
Ambient Temperatures ◽  
Surface Hydroxyl Groups ◽  
Minimization Procedure

We have studied the adsorption of the four isomers of butanol on silicalite and on H-ZSM-5 using an energy minimization procedure supplemented by a Monte Carlo/molecular dynamics algorithm to assist in the location of minima. The energetics and the geometries of adsorption of the butanol isomers in the pores of silicalite and H-ZSM-5 are reported. The effect of the relaxation of both the adsorbent framework and of the adsorbate molecule is investigated. Significant changes in the direction of the surface hydroxyl groups at certain crystallographic positions are induced by alcohol physisorption. For both silicalite and H-ZSM-5, similar energy values were obtained for each butanol isomer sorbed at a number of different crystallographic positions. We therefore predict that there are a range of physisorbed states for all butanols at ambient temperatures. The small variations in the adsorption energetics and sites between isomers may be explained in the terms of pore-confinement effects on the adsorption of molecules with dimensions similar to those of pentasil channels.

Wettability of organically coated tridymite surface – molecular dynamics study

2015 ◽  
Vol 87 (4) ◽  
pp. 405-413 ◽  
Author(s):  
Roland Šolc ◽  
Daniel Tunega ◽  
Martin H. Gerzabek ◽  
Susanne K. Woche ◽  
Jörg Bachmann
Keyword(s):  
Molecular Dynamics ◽  
Md Simulations ◽  
Hydroxyl Groups ◽  
Hydrophobic Contact ◽  
Si Units ◽  
Incomplete Coverage ◽  
Modified Surface ◽  
The Difference ◽  
Silanized Silica ◽  
Glass Surfaces

AbstractClassical molecular dynamics (MD) study was performed in order to explain a different wettability of silanized silica-glass surfaces prepared by using two different precursors – dichlorodimethylsilane (DCDMS) and dimethyldiethoxysilane (DMDES), respectively. Whereas the modified surface prepared by DCDMS becomes hydrophobic (contact angle (CA) of water >90°), DMDES-modified surface stays partially hydrophilic (CA ∼39°). In order to explain the observed discrepancy, several models of surfaces of trydimite with different coating by (CH3)2–Si= units were constructed and treated by water nanodroplets in the MD simulations. The models of surfaces differ by a different degree of surface coverage and/or oligomerized (CH3)2–Si= units in a lateral dimension. The simulations showed that incomplete coverage leads to a decrease of the computed CA, whereas upon lateral oligomerization the CA increases. This variation of the CA is directly related to the accessible amount of the hydroxyl groups on the surfaces and can be a possible explanation of the difference in wettability between DCDMS- and DMDES-treated glass surfaces.

scholarly journals Carbonation Reaction Mechanisms of Portlandite Predicted from Enhanced Ab Initio Molecular Dynamics Simulations

Minerals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 509
Author(s):  
Sylvia M. Mutisya ◽  
Andrey G. Kalinichev
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Reaction Mechanisms ◽  
Co2 Storage ◽  
Direct Interaction ◽  
Ab Initio Molecular Dynamics ◽  
Hydroxyl Groups ◽  
Hydrated Cement ◽  
Carbonation Reaction ◽  
Surface Hydroxyl

Geological carbon capture and sequestration (CCS) is a promising technology for curbing the global warming crisis by reduction of the overall carbon footprint. Degradation of cement wellbore casings due to carbonation reactions in the underground CO2 storage environment is one of the central issues in assessing the long-term success of the CCS operations. However, the complexity of hydrated cement coupled with extreme subsurface environmental conditions makes it difficult to understand the carbonation reaction mechanisms leading to the loss of well integrity. In this work, we use biased ab initio molecular dynamics (AIMD) simulations to explore the reactivity of supercritical CO2 with the basal and edge surfaces of a model hydrated cement phase—portlandite—in dry scCO2 and water-rich conditions. Our simulations show that in dry scCO2 conditions, the undercoordinated edge surfaces of portlandite experience a fast barrierless reaction with CO2, while the fully hydroxylated basal surfaces suppress the formation of carbonate ions, resulting in a higher reactivity barrier. We deduce that the rate-limiting step in scCO2 conditions is the formation of the surface carbonate barrier which controls the diffusion of CO2 through the layer. The presence of water hinders direct interaction of CO2 with portlandite as H2O molecules form well-structured surface layers. In the water-rich environment, CO2 undergoes a concerted reaction with H2O and surface hydroxyl groups to form bicarbonate complexes. We relate the variation of the free-energy barriers in the formation of the bicarbonate complexes to the structure of the water layer at the interface which is, in turn, dictated by the surface chemistry and the degree of nanoconfinement.

Microscopic Wetting at Nanostructured Surface: A Molecular Dynamics Study

2009 ◽  
Author(s):  
Gyoko Nagayama ◽  
Kosuke Yanai ◽  
Kei Kurokawa ◽  
Takaharu Tsuruta
Keyword(s):  
Molecular Dynamics ◽  
Solid Surface ◽  
Phase Interface ◽  
Md Simulations ◽  
Contact Angles ◽  
Pure Liquid ◽  
Nanostructured Surface ◽  
Significant Discrepancy ◽  
Dynamics Simulations ◽  
Solid Liquid

Wettability of the solid surface is a very important property in the micro/nanoscale thermal fluidic systems. In this study, molecular dynamics simulations were carried out to study the microscopic wetting characteristics at the nanostructured surface and the contacting mode in the vicinity of the solid-liquid-vapor interface. A pure liquid nanodroplet was placed on a solid surface in a shape of molecular-scale unevenness with different height and spacing. The wettability of the solid-liquid interface was examined with evaluating the contact angles at the three-phase interface and the liquid-solid contacting area ratio. The results of the measured contact angles demonstrated that the nanostructures could strengthen the hydrophobic properties for a partial wetting condition, while it was insignificant in a completely wetting case. Furthermore, we compared the results of molecular dynamics (MD) simulations to the classical descriptions of Wenzel’s model and Cassie-Baxter’s model. Significant discrepancy among the results was found and a new model of contact angle in consideration of liquid filling ratio among nanostructures was proposed.

Efficient Treatment of Fixed and Induced Dipolar Interactions

2000 ◽  
Vol 653 ◽  
Author(s):  
Celeste Sagui ◽  
Thoma Darden
Keyword(s):  
Molecular Dynamics ◽  
Md Simulations ◽  
Lagrangian Formalism ◽  
Dipolar Interactions ◽  
Time Step ◽  
Efficient Treatment ◽  
Particle Mesh Ewald ◽  
Fixed Charges ◽  
Self Consistency ◽  
Induced Dipoles

AbstractFixed and induced point dipoles have been implemented in the Ewald and Particle-Mesh Ewald (PME) formalisms. During molecular dynamics (MD) the induced dipoles can be propagated along with the atomic positions either by interation to self-consistency at each time step, or by a Car-Parrinello (CP) technique using an extended Lagrangian formalism. The use of PME for electrostatics of fixed charges and induced dipoles together with a CP treatment of dipole propagation in MD simulations leads to a cost overhead of only 33% above that of MD simulations using standard PME with fixed charges, allowing the study of polarizability in largemacromolecular systems.

Split the Charge Difference in Two! a Rule of Thumb for Adding Proper Amounts of Ions in MD Simulations

2020 ◽  
Author(s):  
Matías R. Machado ◽  
Sergio Pantano
Keyword(s):  
Molecular Dynamics ◽  
Ionic Strength ◽  
Molecular Simulations ◽  
Md Simulations ◽  
Good Practices ◽  
Rule Of Thumb ◽  
Ionic Concentrations

<p> Despite the relevance of properly setting ionic concentrations in Molecular Dynamics (MD) simulations, methods or practical rules to set ionic strength are scarce and rarely documented. Based on a recently proposed thermodynamics method we provide an accurate rule of thumb to define the electrolytic content in simulation boxes. Extending the use of good practices in setting up MD systems is promptly needed to ensure reproducibility and consistency in molecular simulations.</p>

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