Structure and dynamics of water at the mackinawite (001) surface

Terranova, Umberto; Leeuw, Nora H. de

doi:10.1063/1.4942755

Cited by 12 publications

(7 citation statements)

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“…All the FeS surfaces were stabilized through hydration, as is perhaps to be expected because the adsorbed water molecules stabilize the low-coordinated surface atoms. At the FeS(001) surface, we found that the water molecules were only physisorbed with the hydrogen atoms pointing toward the terminating surface sulfur ions (Figure 2a), similar to results obtained from previous DFT, 53,62 and molecular dynamics (MD) simulations 65 of the structure and dynamics of water at the FeS(001) surface. The shortest H–S distance is calculated at 2.319 Å, which is larger than the typical hydrogen-bond length in water of 1.97 Å, 66 and therefore suggests that dispersion forces may play an important role in stabilizing the water molecule on the FeS(001) surface.…”

Section: Results and Discussionsupporting

confidence: 89%

Structures and Properties of As(OH)₃ Adsorption Complexes on Hydrated Mackinawite (FeS) Surfaces: A DFT-D2 Study

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Roldán

Leeuw

2017

Environ. Sci. Technol.

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Reactive mineral–water interfaces exert control on the bioavailability of contaminant arsenic species in natural aqueous systems. However, the ability to accurately predict As surface complexation is limited by the lack of molecular-level understanding of As–water–mineral interactions. In the present study, we report the structures and properties of the adsorption complexes of arsenous acid (As(OH)3) on hydrated mackinawite (FeS) surfaces, obtained from density functional theory (DFT) calculations. The fundamental aspects of the adsorption, including the registries of the adsorption complexes, adsorption energies, and structural parameters are presented. The FeS surfaces are shown to be stabilized by hydration, as is perhaps to be expected because the adsorbed water molecules stabilize the low-coordinated surface atoms. As(OH)3 adsorbs weakly at the water–FeS(001) interface through a network of hydrogen-bonded interactions with water molecules on the surface, with the lowest-energy structure calculated to be an As–up outer-sphere complex. Compared to the water–FeS(001) interface, stronger adsorption was calculated for As(OH)3 on the water–FeS(011) and water–FeS(111) interfaces, characterized by strong hybridization between the S-p and O-p states of As(OH)3 and the surface Fe-d states. The As(OH)3 molecule displayed a variety of chemisorption geometries on the water–FeS(011) and water–FeS(111) interfaces, where the most stable configuration at the water–FeS(011) interface is a bidentate Fe–AsO–Fe complex, but on the water–FeS(111) interface, a monodentate Fe–O–Fe complex was found. Detailed information regarding the adsorption mechanisms has been obtained via projected density of states (PDOS) and electron density difference iso-surface analyses and vibrational frequency assignments of the adsorbed As(OH)3 molecule.

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Section: Results and Discussionsupporting

confidence: 89%

Structures and Properties of As(OH)₃ Adsorption Complexes on Hydrated Mackinawite (FeS) Surfaces: A DFT-D2 Study

Dzade

Roldán

Leeuw

2017

Environ. Sci. Technol.

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“…Second, if lipid membranes or simple protocells line the thin inorganic barriers (which have hydrophobic surfaces [75][76][77]), then the steepness of the proton gradient would depend on several factors: (i) the proton permeability of the wall itself; (ii) the flow rates through neighbouring pores (potentially some distance away); and (iii) the proton permeability of the lipid membrane lining the pore. It is feasible that the main barrier to proton flux -responsible for steepening natural pH gradients -is not the inorganic walls themselves but the lipid membranes lining and insulating them (Figure 1).…”

Section: Proton Flux Across Lipid Membranes and Through Protein Machinesmentioning

confidence: 99%

Proton gradients at the origin of life

Lane

2017

BioEssays

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Chemiosmotic coupling - the harnessing of electrochemical ion gradients across membranes to drive metabolism - is as universally conserved as the genetic code. As argued previously in these pages, such deep conservation suggests that ion gradients arose early in evolution, and might have played a role in the origin of life. Alkaline hydrothermal vents harbour pH gradients of similar polarity and magnitude to those employed by modern cells, one of many properties that make them attractive models for life's origin. Their congruence with the physiology of anaerobic autotrophs that use the acetyl CoA pathway to fix CO gives the alkaline vent model broad appeal to biologists. Recently, however, a paper by Baz Jackson criticized the hypothesis, concluding that natural pH gradients were unlikely to have played any role in the origin of life. Unfortunately, Jackson mainly criticized his own interpretations of the theory, not what the literature says. This counterpoint is intended to set the record straight.

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“…The optimised adsorption geometries of water on the different FeS surfaces are shown in Figure 3, and the calculated adsorption energies, optimized geometry parameters, and vibrational frequencies are listed in Table I. On the FeS{001}, we considered different high-symmetry sites and found that the water molecule interacts very weakly with the hydrogen atoms pointing toward surface sulfur atoms, 74,75 releasing an adsorption energy of 0.15 eV. The contribution from the dispersion correction to this adsorption energy is 0.13 eV, which is about 87% of the total value, highlighting the importance of dispersion forces on stabilising the water molecule on the FeS{001} surfaces.…”

Section: A H 2 O Adsorption On Fes Surfacesmentioning

confidence: 99%

DFT-D2 simulations of water adsorption and dissociation on the low-index surfaces of mackinawite (FeS)

Dzade

Roldán

Leeuw

2016

The Journal of Chemical Physics

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The adsorption and dissociation of water on mackinawite (layered FeS) surfaces were studied using dispersion-corrected density functional theory (DFT-D2) calculations. The catalytically active sites for H2O and its dissociated products on the FeS {001}, {011}, {100}, and {111} surfaces were determined, and the reaction energetics and kinetics of water dissociation were calculated using the climbing image nudged elastic band technique. Water and its dissociation products are shown to adsorb more strongly onto the least stable FeS{111} surface, which presents low-coordinated cations in the surface, and weakest onto the most stable FeS{001} surface. The adsorption energies decrease in the order FeS{111} > FeS{100} > FeS{011} > FeS{001}. Consistent with the superior reactivity of the FeS{111} surface towards water and its dissociation products, our calculated thermochemical energies and activation barriers suggest that the water dissociation reaction will take place preferentially on the FeS nanoparticle surface with the {111} orientation. These findings improve our understanding of how the different FeS surface structures and the relative stabilities dictate their reactivity towards water adsorption and dissociation.

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Structure and dynamics of water at the mackinawite (001) surface

Cited by 12 publications

References 49 publications

Structures and Properties of As(OH)₃ Adsorption Complexes on Hydrated Mackinawite (FeS) Surfaces: A DFT-D2 Study

Structures and Properties of As(OH)₃ Adsorption Complexes on Hydrated Mackinawite (FeS) Surfaces: A DFT-D2 Study

Proton gradients at the origin of life

DFT-D2 simulations of water adsorption and dissociation on the low-index surfaces of mackinawite (FeS)

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Structure and dynamics of water at the mackinawite (001) surface

Cited by 12 publications

References 49 publications

Structures and Properties of As(OH)3 Adsorption Complexes on Hydrated Mackinawite (FeS) Surfaces: A DFT-D2 Study

Structures and Properties of As(OH)3 Adsorption Complexes on Hydrated Mackinawite (FeS) Surfaces: A DFT-D2 Study

Proton gradients at the origin of life

DFT-D2 simulations of water adsorption and dissociation on the low-index surfaces of mackinawite (FeS)

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About

Structures and Properties of As(OH)₃ Adsorption Complexes on Hydrated Mackinawite (FeS) Surfaces: A DFT-D2 Study

Structures and Properties of As(OH)₃ Adsorption Complexes on Hydrated Mackinawite (FeS) Surfaces: A DFT-D2 Study