ReaxFF Molecular Dynamics Simulations of Hydroxylation Kinetics for Amorphous and Nano-Silica Structure, and Its Relations with Atomic Strain Energy

Jejoon Yeon, Adri C.T. Van Duin

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39 Citations (Scopus)

Abstract

We performed reactive force field molecular dynamics simulation to observe the hydrolysis reactions between water molecules and locally strained SiO2 geometry. We optimized the force field from J. Fogarty et al. 2010, to more accurately describe the hydroxylation reaction barrier for strained and nonstrained Si - O structures, which are about 20 and 30 kcal/mol, respectively. After optimization, energy barrier for the hydroxylation shows a good agreement with DFT data. The observation of silanol formation at the high-strain region of a silica nanorod also supports the concept that the adsorption of water molecule: hydroxyl formation favors the geometry with higher strain energy. In addition, we found three distinct hydroxylation paths - H3O+ formation reaction from the adsorbed water, proton donation from H3O+, and the direct dissociation of the adsorbed water molecule. Because water molecules and their hydrogen bond network behave differently with respect to temperature ranges, silanol formation is also affected by the temperature. The formation of surface hydroxyl in an amorphous silica double slit displays a similar tendency: SiOH formation prefers high-strain sites. Silanol formation related with H3O+ formation and dissociation is observed in hydroxylation of amorphous SiO2, similar to the results from silica nano wire simulation. These results are particularly relevant to the tribological characteristics of surfaces, enabling the prediction of the attachment site of the lubrication film on silica surfaces with a locally strained geometry.

Original languageEnglish (US)
Pages (from-to)305-317
Number of pages13
JournalJournal of Physical Chemistry C
Volume120
Issue number1
DOIs
StatePublished - Jan 21 2016

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Hydroxylation
Strain energy
Silicon Dioxide
Molecular dynamics
Silica
molecular dynamics
silicon dioxide
Kinetics
Water
Computer simulation
kinetics
Molecules
simulation
Hydroxyl Radical
Geometry
energy
water
field theory (physics)
Energy barriers
molecules

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

Cite this

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title = "ReaxFF Molecular Dynamics Simulations of Hydroxylation Kinetics for Amorphous and Nano-Silica Structure, and Its Relations with Atomic Strain Energy",
abstract = "We performed reactive force field molecular dynamics simulation to observe the hydrolysis reactions between water molecules and locally strained SiO2 geometry. We optimized the force field from J. Fogarty et al. 2010, to more accurately describe the hydroxylation reaction barrier for strained and nonstrained Si - O structures, which are about 20 and 30 kcal/mol, respectively. After optimization, energy barrier for the hydroxylation shows a good agreement with DFT data. The observation of silanol formation at the high-strain region of a silica nanorod also supports the concept that the adsorption of water molecule: hydroxyl formation favors the geometry with higher strain energy. In addition, we found three distinct hydroxylation paths - H3O+ formation reaction from the adsorbed water, proton donation from H3O+, and the direct dissociation of the adsorbed water molecule. Because water molecules and their hydrogen bond network behave differently with respect to temperature ranges, silanol formation is also affected by the temperature. The formation of surface hydroxyl in an amorphous silica double slit displays a similar tendency: SiOH formation prefers high-strain sites. Silanol formation related with H3O+ formation and dissociation is observed in hydroxylation of amorphous SiO2, similar to the results from silica nano wire simulation. These results are particularly relevant to the tribological characteristics of surfaces, enabling the prediction of the attachment site of the lubrication film on silica surfaces with a locally strained geometry.",
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AB - We performed reactive force field molecular dynamics simulation to observe the hydrolysis reactions between water molecules and locally strained SiO2 geometry. We optimized the force field from J. Fogarty et al. 2010, to more accurately describe the hydroxylation reaction barrier for strained and nonstrained Si - O structures, which are about 20 and 30 kcal/mol, respectively. After optimization, energy barrier for the hydroxylation shows a good agreement with DFT data. The observation of silanol formation at the high-strain region of a silica nanorod also supports the concept that the adsorption of water molecule: hydroxyl formation favors the geometry with higher strain energy. In addition, we found three distinct hydroxylation paths - H3O+ formation reaction from the adsorbed water, proton donation from H3O+, and the direct dissociation of the adsorbed water molecule. Because water molecules and their hydrogen bond network behave differently with respect to temperature ranges, silanol formation is also affected by the temperature. The formation of surface hydroxyl in an amorphous silica double slit displays a similar tendency: SiOH formation prefers high-strain sites. Silanol formation related with H3O+ formation and dissociation is observed in hydroxylation of amorphous SiO2, similar to the results from silica nano wire simulation. These results are particularly relevant to the tribological characteristics of surfaces, enabling the prediction of the attachment site of the lubrication film on silica surfaces with a locally strained geometry.

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