Structure and dynamics of the water films confined between edges of pyrophyllite: A first principle study

Churakov, Sergey V.

doi:10.1016/j.gca.2006.11.026

Cited by 69 publications

(74 citation statements)

References 77 publications

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“…It indicates that this site behaves as a basic group. This is very similar to "Al-OSi" sites on (1 1 0) interface of 2:1 phyllosilicates (Churakov, 2007;Liu et al, 2012). The O of "Al-O-Si" group directly contacts with water and it can serve as an important metal complexing site.…”

Section: (1 1 0)-1supporting

confidence: 64%

“…The similar saturation way has been employed in previous simulation studies of 2:1 type phyllosilicates (e.g. Churakov, 2006Churakov, , 2007Liu et al, 2008b).…”

Section: Systemsmentioning

confidence: 99%

“…Cygan, 2001;Bickmore et al, 2003;Cygan et al, 2004Cygan et al, , 2009Boulet et al, 2006;Greenwell et al, 2003Greenwell et al, , 2006Liu and Lu, 2006;Churakov, 2006Churakov, , 2007Kubicki et al, 2007;Rotenberg et al, 2007;Liu et al, 2007Liu et al, , 2008aLiu et al, , 2008bLiu et al, , 2011Liu et al, , 2012 and has proven a powerful complement to experiments. Among various simulation techniques, quantum mechanical method is particularly strong in studying reactive processes.…”

Section: Introductionmentioning

confidence: 99%

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Atomic scale structures of interfaces between kaolinite edges and water

Liu

Wang

et al. 2012

Geochimica et Cosmochimica Acta

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This paper reports the atomic scale structures of kaolinite edge surfaces in contact with water. The commonly occurring edge surfaces are investigated (i.e. (0 1 0) and (1 1 0)) by using first principles molecular dynamics (FPMD) technique. For (1 1 0)-type edge surface, there are two different surface topologies (denoted as (1 1 0)-1 and (1 1 0)-2) and they are considered separately.By using constrained FPMD technique, the free-energy changes for the leaving processes of water ligands of O-sheet Al cations have been calculated and thus, the coordination states of those Al cations are determined. The results show that for (0 1 0) and (1 1 0)-2 edges, both the 5 and 6-fold coordination states are possible whereas for (1 1 0)-1 edges, only the 6-fold states are stable. Based on the analyses of H-bonding structures at the interfaces, the surface acid/base reactive sites are illustrated. (1) T-sheet groups are "Si-OH, behaving as both proton donors and acceptors. (2) Bridging oxygen At (0 1 0) and (1 1 0)-2 edges, these sites are inaccessible from the water and thus, they are not effective reactive sites. At (1 1 0)-1 edges, the bridging oxygen atoms are proton accepting sites. (3) O-sheet groups At (0 1 0) and (1 1 0)-2 edges, for 6-fold Al cases, the active surface groups are "Al-(OH)(OH 2 ) and for the 5-fold Al cases, the active surface groups are "Al-(OH). At (1 1 0)-1 edges, the active site is "Al-OH 2 . This study provides fundamental structural properties for understanding the interface chemistry of widely occurring 1:1 type phyllosilicates.

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Section: (1 1 0)-1supporting

confidence: 64%

“…The similar saturation way has been employed in previous simulation studies of 2:1 type phyllosilicates (e.g. Churakov, 2006Churakov, , 2007Liu et al, 2008b).…”

Section: Systemsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Atomic scale structures of interfaces between kaolinite edges and water

Liu

Wang

et al. 2012

Geochimica et Cosmochimica Acta

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“…The application of quantum-mechanical simulations has significantly promoted interface geochemistry research in areas that are difficult to explore with experimental approaches (e.g., Cygan, 2001;Sherman, 2001;Bickmore et al, 2003Bickmore et al, , 2006Greenwell et al, 2003Greenwell et al, , 2006Boulet et al, 2006;Churakov, 2006Churakov, , 2007Kubicki et al, 2007Kubicki et al, , 2008Rotenberg et al, 2007Rotenberg et al, , 2010Tunega et al, 2007;Cygan et al, 2009;Churakov and Kosakowski, 2010). Using static quantum calculations, Bickmore et al (2003) optimized (0 1 0) and (1 1 0) surfaces of neutral 2:1 phyllosilicates (octahedral cations are Al(III) and Fe(III), respectively) and calculated the acidity constants of edge hydroxyls.…”

Section: Introductionmentioning

confidence: 99%

“…The major shortcoming of static calculations is the oversimplification of solvent effects, which leads to an inaccurate treatment of entropy contributions. Churakov (2007) employed FPMD simulations to study the interfaces between pyrophyllite edges and confined water films. According to these simulation studies, it is revealed that under pH conditions close to the PZC (point of zero charge), the stable surface group in T-sheets is "SiAOH, and "AlA(OH)(OH 2 ) and "FeA(OH)(OH 2 ) are stable in O-sheets.…”

Section: Introductionmentioning

confidence: 99%

Atomic-scale structures of interfaces between phyllosilicate edges and water

Liu

Meijer

et al. 2012

Geochimica et Cosmochimica Acta

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We report first-principles molecular dynamics (FPMD) studies on the structures of interfaces between phyllosilicate edges and water. Using FPMD, the substrates and solvents are simulated at the same first-principles level, and the thermal motions are sampled via molecular dynamics. Both the neutral and charged silicate frameworks are considered, and for charged cases, the octahedral (Mg for Al) and tetrahedral (Al for Si) substitutions are taken into account. For all frameworks, we focus on the commonly occurring (0 1 0)-and (1 1 0)-type edge surfaces.With constrained FPMD, we calculated the free energy of the leaving processes of coordinated water of octahedral cations; therefore, the coordination states of those edge cations are determined. For (0 1 0)-type edges, both the 5-and 6-fold coordination states of Al are stable and occur with a similar probability, whereas only the 5-fold coordination is stable for Mg cations. For (1 1 0)-type edges, only the 6-fold states of Al cations are stable. However, for Mg cations, both coordination states are stable. In the 5-fold case, the solvent water molecules form H-bonds with the bridging oxygen atoms (i.e., "MgAOASi"). The free energy results indicate that there should be a considerable number of 5-fold coordinated octahedral sites (i.e., "MgAOH/ "AlAOH) at the interfaces. The interfacial structures and acid/base groups were determined by detailed H-bonding analyses.(1) Bridging oxygen sites. For (0 1 0) edges, the bridging oxygen atoms are not effective proton-accepting sites because they are inaccessible from the solvent. For (1 1 0) edges, the oxygen atoms of neutral and octahedrally substituted frameworks (i.e., "MAOASi" for M@Al/Mg) are proton-accepting sites. For T-sheet substituted cases, the bridging oxygen site becomes a proton-donating group (i.e., "AlAOHASi") through the capture of a proton. (2) T-sheet groups. All T-sheet edge groups are "MAOH (M@Si/Al) and act as both proton donors and acceptors. (3)O-sheet groups. For (0 1 0) edges with 6-fold Al, the active surface groups include "AlA(OH)(H 2 O) and "AlA(OH) 2 , whereas for Mg cations, the edge group is "MgA(OH 2 ) 2 . For 5-fold coordination, the active groups are "AlAOH. At (1 1 0) edges, proton-donating sites include "AlAOH, "AlAOH 2 and "MgAOH 2 groups. Overall, our results reveal the significant effects of isomorphic substitutions on the interfacial structures, and the models provide a molecular-level basis for understanding relevant interfacial processes.

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Mineral–Water Interaction

Gaigeot

Sulpizi

2016

Molecular Modeling of Geochemical Reactions

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Structure and dynamics of the water films confined between edges of pyrophyllite: A first principle study

Cited by 69 publications

References 77 publications

Atomic scale structures of interfaces between kaolinite edges and water

Atomic scale structures of interfaces between kaolinite edges and water

Atomic-scale structures of interfaces between phyllosilicate edges and water

Mineral–Water Interaction

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