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You searched for subject:(aqueous interfaces). Showing records 1 – 3 of 3 total matches.

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1. Sayer, Thomas. Establishing faithful simulation of polar surfaces in contact with the aqueous phase.

Degree: PhD, 2020, University of Cambridge

Crystal surfaces which generate polar repeat units are fundamentally unstable on electrostatic grounds. As such, they require a charge-compensation mechanism if they are to exist at all. In vacuo, this usually presents as a self-ionisation (electronic reconstruction), or a non-stoichiometric reconstruction of the surface region. When a fluid is present, charge can also be provided externally by adsorbates. In this thesis, we will use molecular dynamics (MD) simulation to investigate the potential of an aqueous phase to stabilise several polar surfaces. Firstly, we address certain finite-size effects by using finite field Hamiltonians developed by Stengel, Spaldin and Vanderbilt and recently introduced to MD. We show that for the simple model of a sodium chloride (111) slab, treated with a forcefield, an electrolyte can provide charge compensation. Next, we compare our boundary conditions to those used in published work on polar silver iodide in the context of ice nucleation. We demonstrate that standard `dipole-correction' methods fail to describe not only the crystal, but also the aqueous phase. Moving forwards, we test the robustness of our method by performing ab initio MD on our NaCl (111) slab. This highlights several technical nuances whilst also allowing us to directly evaluate the role of the electronic degrees of freedom in the presence of such polarising conditions. Passing these validating steps, we investigate magnesium oxide in contact with the aqueous phase: firstly the non-polar (100) termination, which exhibits complicated water dissociation at the interface; and secondly the polar (111) termination, which forces us to evaluate our model in the face of some much more aggressive chemistry. Finally, we reflect on all the accrued queries which remain to be tackled by theory and simulation.

Subjects/Keywords: 541; Interfaces; Dielectrics; Molecular Dynamics; Chemistry; Polar Surfaces; Aqueous Electrolyte; Electrostatics

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Sayer, T. (2020). Establishing faithful simulation of polar surfaces in contact with the aqueous phase. (Doctoral Dissertation). University of Cambridge. Retrieved from https://doi.org/10.17863/CAM.54890 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.810127

Chicago Manual of Style (16th Edition):

Sayer, Thomas. “Establishing faithful simulation of polar surfaces in contact with the aqueous phase.” 2020. Doctoral Dissertation, University of Cambridge. Accessed May 08, 2021. https://doi.org/10.17863/CAM.54890 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.810127.

MLA Handbook (7th Edition):

Sayer, Thomas. “Establishing faithful simulation of polar surfaces in contact with the aqueous phase.” 2020. Web. 08 May 2021.

Vancouver:

Sayer T. Establishing faithful simulation of polar surfaces in contact with the aqueous phase. [Internet] [Doctoral dissertation]. University of Cambridge; 2020. [cited 2021 May 08]. Available from: https://doi.org/10.17863/CAM.54890 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.810127.

Council of Science Editors:

Sayer T. Establishing faithful simulation of polar surfaces in contact with the aqueous phase. [Doctoral Dissertation]. University of Cambridge; 2020. Available from: https://doi.org/10.17863/CAM.54890 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.810127

2. Sayer, Thomas. Establishing Faithful Simulation of Polar Surfaces in Contact with the Aqueous Phase.

Degree: PhD, 2020, University of Cambridge

Crystal surfaces which generate polar repeat units are fundamentally unstable on electrostatic grounds. As such, they require a charge-compensation mechanism if they are to exist at all. In vacuo, this usually presents as a self-ionisation (electronic reconstruction), or a non-stoichiometric reconstruction of the surface region. When a fluid is present, charge can also be provided externally by adsorbates. In this thesis, we will use molecular dynamics (MD) simulation to investigate the potential of an aqueous phase to stabilise several polar surfaces. Firstly, we address certain finite-size effects by using finite field Hamiltonians developed by Stengel, Spaldin and Vanderbilt and recently introduced to MD. We show that for the simple model of a sodium chloride (111) slab, treated with a forcefield, an electrolyte can provide charge compensation. Next, we compare our boundary conditions to those used in published work on polar silver iodide in the context of ice nucleation. We demonstrate that standard `dipole-correction' methods fail to describe not only the crystal, but also the aqueous phase. Moving forwards, we test the robustness of our method by performing ab initio MD on our NaCl (111) slab. This highlights several technical nuances whilst also allowing us to directly evaluate the role of the electronic degrees of freedom in the presence of such polarising conditions. Passing these validating steps, we investigate magnesium oxide in contact with the aqueous phase: firstly the non-polar (100) termination, which exhibits complicated water dissociation at the interface; and secondly the polar (111) termination, which forces us to evaluate our model in the face of some much more aggressive chemistry. Finally, we reflect on all the accrued queries which remain to be tackled by theory and simulation.

Subjects/Keywords: Interfaces; Dielectrics; Molecular Dynamics; Chemistry; Polar Surfaces; Aqueous Electrolyte; Electrostatics

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Sayer, T. (2020). Establishing Faithful Simulation of Polar Surfaces in Contact with the Aqueous Phase. (Doctoral Dissertation). University of Cambridge. Retrieved from https://www.repository.cam.ac.uk/handle/1810/307798

Chicago Manual of Style (16th Edition):

Sayer, Thomas. “Establishing Faithful Simulation of Polar Surfaces in Contact with the Aqueous Phase.” 2020. Doctoral Dissertation, University of Cambridge. Accessed May 08, 2021. https://www.repository.cam.ac.uk/handle/1810/307798.

MLA Handbook (7th Edition):

Sayer, Thomas. “Establishing Faithful Simulation of Polar Surfaces in Contact with the Aqueous Phase.” 2020. Web. 08 May 2021.

Vancouver:

Sayer T. Establishing Faithful Simulation of Polar Surfaces in Contact with the Aqueous Phase. [Internet] [Doctoral dissertation]. University of Cambridge; 2020. [cited 2021 May 08]. Available from: https://www.repository.cam.ac.uk/handle/1810/307798.

Council of Science Editors:

Sayer T. Establishing Faithful Simulation of Polar Surfaces in Contact with the Aqueous Phase. [Doctoral Dissertation]. University of Cambridge; 2020. Available from: https://www.repository.cam.ac.uk/handle/1810/307798

3. Pezzotti, Simone. DFT-MD simulations and theoretical SFG spectroscopy to characterize H-Bonded networks at aqueous interfaces : from hydrophobic to hydrophilic environments : Simulations DFT-MD et spectroscopie SFG théorique pour la caractérisation des interfaces aqueuses : des environnements hydrophobes à hydrophiles.

Degree: Docteur es, Chimie, 2019, Université Paris-Saclay (ComUE)

Améliorer notre connaissance de la structure de l'eau dans l'environnement spécial offert par une interface est essentiel pour la compréhension de nombreux phénomènes naturels et applications technologiques. Pour révéler cette structure interfaciale de l'eau, des techniques capables de fournir des informations microscopiques, de manière sélective, pour cette couche interfaciale (BIL) sont nécessaires. Dans le présent travail de thèse, nous avons donc étudié les interfaces aqueuses au niveau moléculaire, en couplant la modélisation théorique à partir de simulations DFT-MD avec les spectroscopies SFG et THz-IR. En développant de nouveaux protocoles/outils d'investigation associant simulations DFT-MD et spectroscopie SFG, en particulier pour la rationalisation plus complexe des interfaces chargées, nous avons fourni une compréhension globale de l'effet des conditions interfaciales d'hydrophilicité, de pH, de force ionique sur le réseau des liaisons-H formé dans la couche interfaciale BIL, sur ses signatures spectroscopiques et sur son impact sur les propriétés physico-chimiques. Nous avons montré pour la première fois que, dans des conditions suffisamment hydrophobes, l'eau interfaciale crée des réseaux des liaisons-H bidimensionnels, révélé expérimentalement par les spectres THz-IR. Le réseau-2D dicte la dynamique de l'eau interfaciale, le potentiel de surface, l'acidité de surface, la tension superficielle et la thermodynamique d'hydratation des solutés hydrophobes. Cet "ordre horizontal" aux interfaces hydrophobes est opposé à "l'ordre verticale" obtenu aux interfaces hydrophiles. Nous avons aussi révélé comment les ions et les conditions de pH modifient ces arrangements structuraux.

Improving our knowledge on water H-Bonded networks formed in the special environment offered by an interface is pivotal for our understanding of many natural phenomena and technological applications. To reveal the interfacial water arrangement, techniques able to provide detailed microscopic information selectively for the interfacial layer are required. In the present thesis work, we have hence investigated aqueous interfaces at the molecular level, by coupling theoretical modeling from DFT-MD simulations with SFG & THz-IR spectroscopies. By developing new investigation protocols/tools, coupling DFT-MD simulations and SFG spectroscopy, in particular for the more complex rationalization of charged interfaces, we have provided a global comprehension of the effect of various interfacial conditions (hydrophilicity, pH, ionic strength) on the HB-Network formed in the interfacial layer (BIL), on its spectroscopic signatures and on its impact on physico-chemical properties. We have shown for the first time that, in sufficiently hydrophobic conditions, BIL interfacial water creates special 2-Dimensional HB-Networks, experimentally revealed by one specific THz-IR marker band. Such 2D-network dictates HBs and orientational dynamics of interfacial water, surface potential, surface acidity, water surface tension and thermodynamics of hydration…

Advisors/Committee Members: Gaigeot, Marie-Pierre (thesis director).

Subjects/Keywords: Dft-Md; Sfg; Interfaces aqueuses; THz-IR; Hydrophobicité; Bil/dl; Dft-Md; Sfg; Aqueous interfaces; THz-IR; Hydrophobicity; Bil/dl

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Pezzotti, S. (2019). DFT-MD simulations and theoretical SFG spectroscopy to characterize H-Bonded networks at aqueous interfaces : from hydrophobic to hydrophilic environments : Simulations DFT-MD et spectroscopie SFG théorique pour la caractérisation des interfaces aqueuses : des environnements hydrophobes à hydrophiles. (Doctoral Dissertation). Université Paris-Saclay (ComUE). Retrieved from http://www.theses.fr/2019SACLE008

Chicago Manual of Style (16th Edition):

Pezzotti, Simone. “DFT-MD simulations and theoretical SFG spectroscopy to characterize H-Bonded networks at aqueous interfaces : from hydrophobic to hydrophilic environments : Simulations DFT-MD et spectroscopie SFG théorique pour la caractérisation des interfaces aqueuses : des environnements hydrophobes à hydrophiles.” 2019. Doctoral Dissertation, Université Paris-Saclay (ComUE). Accessed May 08, 2021. http://www.theses.fr/2019SACLE008.

MLA Handbook (7th Edition):

Pezzotti, Simone. “DFT-MD simulations and theoretical SFG spectroscopy to characterize H-Bonded networks at aqueous interfaces : from hydrophobic to hydrophilic environments : Simulations DFT-MD et spectroscopie SFG théorique pour la caractérisation des interfaces aqueuses : des environnements hydrophobes à hydrophiles.” 2019. Web. 08 May 2021.

Vancouver:

Pezzotti S. DFT-MD simulations and theoretical SFG spectroscopy to characterize H-Bonded networks at aqueous interfaces : from hydrophobic to hydrophilic environments : Simulations DFT-MD et spectroscopie SFG théorique pour la caractérisation des interfaces aqueuses : des environnements hydrophobes à hydrophiles. [Internet] [Doctoral dissertation]. Université Paris-Saclay (ComUE); 2019. [cited 2021 May 08]. Available from: http://www.theses.fr/2019SACLE008.

Council of Science Editors:

Pezzotti S. DFT-MD simulations and theoretical SFG spectroscopy to characterize H-Bonded networks at aqueous interfaces : from hydrophobic to hydrophilic environments : Simulations DFT-MD et spectroscopie SFG théorique pour la caractérisation des interfaces aqueuses : des environnements hydrophobes à hydrophiles. [Doctoral Dissertation]. Université Paris-Saclay (ComUE); 2019. Available from: http://www.theses.fr/2019SACLE008

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