scholarly journals Solvation Free Energies and Adsorption Energies at the Metal/Water Interface from Hybrid Quantum-Mechanical/Molecular Mechanics Simulations

2020 ◽  
Vol 16 (10) ◽  
pp. 6539-6549
Author(s):  
Paul Clabaut ◽  
Benjamin Schweitzer ◽  
Andreas W. Götz ◽  
Carine Michel ◽  
Stephan N. Steinmann
Keyword(s):  
Molecular Mechanics ◽  
Quantum Mechanical ◽  
Water Interface ◽  
Free Energies ◽  
Adsorption Energies ◽  
Solvation Free Energies ◽  
Metal Water

Solvation Free Energies and Adsorption Energies at the Metal/Water Interface from Hybrid QM-MM Simulations

2020 ◽  
Author(s):  
Paul Clabaut ◽  
Benjamin Schweitzer ◽  
Andreas Goetz ◽  
Carine Michel ◽  
Stephan Steinmann
Keyword(s):  
Free Energy ◽  
Adsorption Energy ◽  
Metallic Surface ◽  
Implicit Solvent ◽  
Water Interface ◽  
Free Energies ◽  
Hybrid Scheme ◽  
Aromatic Molecules ◽  
Solvent Model ◽  
Metal Water

Modeling adsorption at the metal/water interfaces is a corner-stone towards an improved understanding in a variety of fields from heterogeneous catalysis to corrosion. We propose and validate a hybrid scheme that combines the adsorption free energies obtained in gas phase at the DFT level with the variation in solvation from the bulk phase to the interface evaluated using a molecular mechanics based alchemical transformation, denoted MMsolv. Using the GAL17 force field for the platinum/water interaction, we retrieve a qualitatively correct interaction energy of the water solvent at the interface. This interaction is of near chemisorption character and thus challenging, both for the alchemical transformation, but also for the fixed point-charge electrostatics. Our scheme passes through a state characterized by a well-behaved physisorption potential for the Pt(111)/H<sub>2</sub>O interaction to converge the free energy difference. The workflow is implemented in the freely available SolvHybrid package. We first assess the adsorption of a water molecule at the Pt/water interface, which turns out to be a stringent test. The intrinsic error of our QM-MM hybrid scheme is limited to 6 kcal/mol through the introduction of a correction term to attenuate the electrostatic interaction between near-chemisorbed water molecules and the underlying Pt atoms. Next, we show that the MMsolv solvation free energy of Pt (-0.46 J/m<sup>2</sup>) is in good agreement with the experimental estimate (-0.32 J/m<sup>2</sup>). Furthermore, we show that the entropy contribution at room temperature is roughly of equal magnitude as the free energy, but with opposite sign. Finally, we compute the adsorption energy of benzene and phenol at the Pt(111)/water interface, one of the rare systems for which experimental data are available. In qualitative agreement with experiment, but in stark contrast with a standard implicit solvent model, the adsorption of these aromatic molecules is strongly reduced (i.e., less exothermic by ~30 and 40 kcal/mol for our QM/MM hybrid scheme and experiment, respectively, but ~0 with the implicit solvent) at the solid/liquid compared to the solid/gas interface. This reduction is mainly due to the competition between the organic adsorbate and the solvent for adsorption on the metallic surface. The semi-quantitative agreement with experimental estimates for the adsorption energy of aromatic molecules thus validates the soundness of our hybrid QM-MM scheme.

scholarly journals Computation of protein–ligand binding free energies using quantum mechanical bespoke force fields

MedChemComm ◽  
2019 ◽  
Vol 10 (7) ◽  
pp. 1116-1120 ◽  
Author(s):  
Daniel J. Cole ◽  
Israel Cabeza de Vaca ◽  
William L. Jorgensen
Keyword(s):  
Ligand Binding ◽  
Force Field ◽  
Molecular Mechanics ◽  
Force Fields ◽  
Quantum Mechanical ◽  
T4 Lysozyme ◽  
Free Energies ◽  
Binding Free Energies

A quantum mechanical bespoke molecular mechanics force field is derived for the L99A mutant of T4 lysozyme and used to compute absolute binding free energies of six benzene analogs to the protein.

scholarly journals Real single ion solvation free energies with quantum mechanical simulation

2017 ◽  
Vol 8 (9) ◽  
pp. 6131-6140 ◽  
Author(s):  
Timothy T. Duignan ◽  
Marcel D. Baer ◽  
Gregory K. Schenter ◽  
Christopher J. Mundy
Keyword(s):  
Ion Pairs ◽  
Electrolyte Solutions ◽  
Ion Solvation ◽  
Quantum Mechanical ◽  
Free Energies ◽  
Ongoing Debate ◽  
Mechanical Simulation ◽  
Solvation Free Energies

Single ion solvation free energies are one of the most important properties of electrolyte solutions and yet there is ongoing debate about what these values are. Only the values for neutral ion pairs are known.

scholarly journals Solvation Free Energies and Adsorption Energies at the Metal/Water Interface from Hybrid QM-MM Simulations

2020 ◽  
Author(s):  
Paul Clabaut ◽  
Benjamin Schweitzer ◽  
Andreas Goetz ◽  
Carine Michel ◽  
Stephan Steinmann
Keyword(s):  
Free Energy ◽  
Adsorption Energy ◽  
Metallic Surface ◽  
Implicit Solvent ◽  
Water Interface ◽  
Free Energies ◽  
Hybrid Scheme ◽  
Aromatic Molecules ◽  
Solvent Model ◽  
Metal Water

Modeling adsorption at the metal/water interfaces is a corner-stone towards an improved understanding in a variety of fields from heterogeneous catalysis to corrosion. We propose and validate a hybrid scheme that combines the adsorption free energies obtained in gas phase at the DFT level with the variation in solvation from the bulk phase to the interface evaluated using a molecular mechanics based alchemical transformation, denoted MMsolv. Using the GAL17 force field for the platinum/water interaction, we retrieve a qualitatively correct interaction energy of the water solvent at the interface. This interaction is of near chemisorption character and thus challenging, both for the alchemical transformation, but also for the fixed point-charge electrostatics. Our scheme passes through a state characterized by a well-behaved physisorption potential for the Pt(111)/H<sub>2</sub>O interaction to converge the free energy difference. The workflow is implemented in the freely available SolvHybrid package. We first assess the adsorption of a water molecule at the Pt/water interface, which turns out to be a stringent test. The intrinsic error of our QM-MM hybrid scheme is limited to 6 kcal/mol through the introduction of a correction term to attenuate the electrostatic interaction between near-chemisorbed water molecules and the underlying Pt atoms. Next, we show that the MMsolv solvation free energy of Pt (-0.46 J/m<sup>2</sup>) is in good agreement with the experimental estimate (-0.32 J/m<sup>2</sup>). Furthermore, we show that the entropy contribution at room temperature is roughly of equal magnitude as the free energy, but with opposite sign. Finally, we compute the adsorption energy of benzene and phenol at the Pt(111)/water interface, one of the rare systems for which experimental data are available. In qualitative agreement with experiment, but in stark contrast with a standard implicit solvent model, the adsorption of these aromatic molecules is strongly reduced (i.e., less exothermic by ~30 and 40 kcal/mol for our QM/MM hybrid scheme and experiment, respectively, but ~0 with the implicit solvent) at the solid/liquid compared to the solid/gas interface. This reduction is mainly due to the competition between the organic adsorbate and the solvent for adsorption on the metallic surface. The semi-quantitative agreement with experimental estimates for the adsorption energy of aromatic molecules thus validates the soundness of our hybrid QM-MM scheme.

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