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Improved Sampling in Ab Initio-Based Free Energy Calculations of Amino Acids at Solid-Liquid Interfaces: A Tight-Binding Assessment on TiO2 Anatase (101)
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Atomistic simulations are powerful for probing molecules at bioinorganic interfaces and excellent complements to scarcely available experimental techniques. The free energy controls the adsorption behavior of molecules on nanosurfaces, and is therefore a quantity of particular importance. Advanced sampling techniques can efficiently explore the adsorption free energy landscape, but molecular simulations with classical (Newtownian) dynamics fail to capture charge transfer and polarization at the solid-liquid interface. First principle simulations do not suffer from this limitation but come with a heavy computational load. Here, we introduce an efficient protocol to explore the free energy of adsorption in the ab initio framework. This approach accurately models the complex phenomena at bio-inorganic surfaces on the nanoscale and properly samples the relevant thermodynamic properties. We present a case study of adsorption of the Lysine and Aspartate amino acids on the anatase (101) TiO2 surface with the tight binding method. The high values of the calculated adsorption free energies highlight the importance of a proper description of the electronic state for surface binding processes.

National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
URN: urn:nbn:se:su:diva-169794OAI: oai:DiVA.org:su-169794DiVA, id: diva2:1325942
Available from: 2019-06-17 Created: 2019-06-17 Last updated: 2019-06-19Bibliographically approved
In thesis
1. Atomistic simulations of structural and dynamical properties of liquids under geometric constraints
Open this publication in new window or tab >>Atomistic simulations of structural and dynamical properties of liquids under geometric constraints
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The statistical-mechanical description of liquids represents a formidable problem in physic due to the absence of the analytical theory of the liquid state. Atomistic simulations represent a unique source of information in this respect and can be implemented in order address macroscopically measurable liquid properties, including its structure and dynamics, based on the information of the interactions between its constituent molecules. A particularly intriguing challenge is represented by the problem of studying liquids under geometric constraints like surfaces, or where the dimensionality is strongly suppressed like for liquids in 2 dimensions. Experimental measurements cannot access to these regions due to the resolution limitations. In this thesis the study of confined liquids is achieved by particle-based simulations at different level of theory. In particular 3 study cases are considered: the first is the characterization of solid-liquid interfaces. The problem of adsorbing surfaces is treated as a specific case of inorganic surfaces in contact with liquid water. TiO2, chosen as reference material, is studied in its polymorphic structures in aqueous conditions. The surface reactivity and its influence on the liquid structure is solved considering the quantum nature of the system. The mechanism of a solute adsorbing at the interface, considering the interfacial liquid properties, is also addressed. New advanced analysis tools for determining the structural and dynamical properties of water under a surface confinement and the thermodynamic associated to relative adsorption processes are developed. We are confident that this study will represent a mile stone for a systematic study of complex environments as bio-inorganic interfaces. As second case a liquid confined in a 2D surface is studied. Simple liquids having spherically symmetric interaction are very powerful in order to understand the relevant degrees of freedom that governs a certain physical process. Here we expand the definition of 2D hexatic phases to smectic systems in 3D. Finally the self-assembly of a triply periodic mesophase having a Fddd space symmetry group is fully characterized for a simple liquid. This phase can be thought as a geometrical reduction to a two-dimensional separation surface. The possibility of generating such complex network with simple particles, like in colloids, opens the frontiers for the exploration of new materials and applications.

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry, Stockholm University, 2019. p. 60
Keywords
liquid, contraint, TiO2, surfaces, bio-inorganic, molecular dynamic, ab-initio, tight-binding, DFT, metadynamic, free energy, nanoparticles, water, amino acids, adsorption, mesophases, hexatic, smectic, triply periodic network, Fddd
National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:su:diva-169817 (URN)978-91-7797-757-5 (ISBN)978-91-7797-758-2 (ISBN)
Public defence
2019-09-05, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 6: Manuscript. Paper 7: Manuscript.

Available from: 2019-08-13 Created: 2019-06-17 Last updated: 2019-08-12Bibliographically approved

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