Surface structure of linear nanopores in amorphous silica: Comparison of properties for different pore generation algorithms

Han, Yong; Slowing, Igor I.; Evans, James W.

doi:10.1063/5.0021317

Cited by 4 publications

(6 citation statements)

References 57 publications

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“…A large number of simulation studies have used crystalline models, such as α-quartz , or β-cristobalite, − ,,,,,− that are atomically smooth. In addition, models of amorphous silica have frequently been based on “cleaving” a solid a-SiO 2 sample and then saturating the resulting under-coordinated atoms, a procedure that also leads to a comparatively flat interface …”

Section: Resultsmentioning

confidence: 99%

“…In addition, models of amorphous silica have frequently been based on "cleaving" a solid a-SiO 2 sample and then saturating the resulting under-coordinated atoms, a procedure that also leads to a comparatively flat interface. 100 Some insights into how surface roughness can impact liquids at the silica interface is offered by vibrational sum-frequency generation (SFG) measurements, 137,138 and some corresponding simulations, 139,140 of both amorphous silica and crystalline quartz interfaces. The experiments show significant differences in the SFG spectra at the water/fused silica and water/(0001) quartz interfaces with this surface-sensitive technique.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…As noted above, the most common method for generating slab or pore models is a melt-quench-cleave-based approach. ,,,− In these simulations, silica is heated to form the liquid and cooled to form an amorphous solid, and this structure is then “cleaved” to generate the desired planar or curved interface. The cleaving step naturally results in a large number of under-coordinated silicon and oxygen atoms that are then terminated by the addition of OH groups and H atoms (and sometimes O atoms).…”

Section: Computational Methodsmentioning

confidence: 99%

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Amorphous Silica Slab Models with Variable Surface Roughness and Silanol Density for Use in Simulations of Dynamics and Catalysis

et al. 2021

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Silica is both ubiquitous in nature and important in a wide range of applications ranging from drug delivery to catalysis. This has spawned significant interest in modeling silica, particularly the amorphous solid, and its interactions with liquids, adsorbates, and embedded active sites. One of the challenges is developing descriptions that accurately represent the synthesized materials used in experiments when key properties, such as the surface roughness and distribution of silanol groups, cannot be readily measured. Here, we implement a simple, tunable melt-cleave-quench-functionalize approach to create amorphous silica slabs with variable characteristics. We use it to generate 2000 atomistically distinct slab models, based on the widely used the van Beest, Kramer, van Santen (BKS) potential, that differ in their atomistic roughness, defect site density, ring distribution, silanol density, and spatial arrangement of silanols. The surfaces are demonstrated to be consistent with available experimental data and stable within the ReaxFF bond order-based reactive force field. These amorphous silica slab models should thus be of use in a variety of computational studies of interfacial properties.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Computational Methodsmentioning

confidence: 99%

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Amorphous Silica Slab Models with Variable Surface Roughness and Silanol Density for Use in Simulations of Dynamics and Catalysis

et al. 2021

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“…The most popular surface for molecular simulation studies of chromatographic systems, the (111) face of β-cristobalite silica, for example, bears only equidistant, single, and isolated silanol groups. A cylindrical pore, whether generated through pore drilling or cylindrical resist algorithms, possesses a certain degree of surface roughness as well as amorphous surface chemistry . These differences in the underlying surface chemistry of cylindrical and slit pores have to be considered (and partially adjusted) during functionalization with the bonded phase to obtain comparable chromatographic surfaces .…”

Section: Introductionmentioning

confidence: 99%

Consequences of Cylindrical Pore Geometry for Interfacial Phenomena in Reversed-Phase Liquid Chromatography

et al. 2021

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The interfacial phenomena behind analyte separation in a reversed-phase liquid chromatography column take place nearly exclusively inside the silica mesopores. Their cylindrical geometry can be expected to shape the properties of the chromatographic interface with consequences for the analyte density distribution and diffusivity. To investigate this topic through molecular dynamics simulations, we introduce a cylindrical pore inside a slit pore configuration, where the inner curved and outer planar silica surface bear the same bonded phase. The present model replicates an average-sized (9 nm) mesopore in an endcapped C 18 column equilibrated with a mobile phase of 70/30 (v/v) water/acetonitrile. Simulations performed for ethylbenzene and acetophenone show that the surface curvature shifts the bonded phase and analyte density toward the pore center, decreases the solvent density in the bonded-phase region, increases the acetonitrile excess in the interfacial region, and considerably enhances the surface diffusivity of both analytes. Overall, the cylindrical pore provides a more hydrophobic environment than the slit pore. Ethylbenzene density is decidedly increased in the cylindrical pore, whereas acetophenone density is nearly equally distributed between the cylindrical and slit pore. The cylindrical pore geometry thus sharpens the discrimination between the apolar and moderately polar analytes while enhancing the mass transport of both.

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“…The second strategy attempts to resemble the synthesis process by lattice Monte Carlo [50][51][52], kinetic Monte Carlo [53,54] or molecular dynamics simulations [55]. The different approaches have been discussed recently by Han et al [56].…”

Section: Introductionmentioning

confidence: 99%

PoreMS: a software tool for generating silica pore models with user-defined surface functionalisation and pore dimensions

Kraus

Rybka

Höltzel

et al. 2021

Molecular Simulation

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Mass transport under confinement is at the heart of all processes employing functionalised mesoporous silica materials, such as liquid chromatography, heterogeneous catalysis, and gas adsorption. Molecular simulation studies of mass transport in such settings require pore models that replicate the geometry, dimensions, and chemical structure of a surface-functionalised silica mesopore. We present a software tool that facilitates rapid model building of functionalised silica pores for systematic studies of confinement effects in various applications of relevant materials. The tool allows to choose the chemical structure and density of the ligands and to control the residual hydroxylation of the silica surface. Individual ligands can be placed at a user-defined position on the surface. Moreover, the tool supports an independent functionalisation of the interior and exterior pore surface. We explain each step of the pore generation, discuss the underlying assumptions and limitations, and introduce examples of generated cylindrical pore models for chromatography and catalysis.

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Surface structure of linear nanopores in amorphous silica: Comparison of properties for different pore generation algorithms

Abstract: Light intensity-dependence studies on the role of surface deposits for titaniaphotocatalyzed oxygen evolution: Are they really cocatalysts?

Cited by 4 publications

References 57 publications

Amorphous Silica Slab Models with Variable Surface Roughness and Silanol Density for Use in Simulations of Dynamics and Catalysis

Amorphous Silica Slab Models with Variable Surface Roughness and Silanol Density for Use in Simulations of Dynamics and Catalysis

Consequences of Cylindrical Pore Geometry for Interfacial Phenomena in Reversed-Phase Liquid Chromatography

PoreMS: a software tool for generating silica pore models with user-defined surface functionalisation and pore dimensions

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