Rigorous pK_a Estimation of Amine Species Using Density-Functional Tight-Binding-Based Metadynamics Simulations

Abstract

Predicting pK values for different types of amine species with high accuracy and efficiency is of critical importance for the design of high performance and economical solvents in carbon capture and storage with aqueous amine solutions. In this study, we demonstrate that density-functional tight-binding-based metadynamics simulations are a promising approach to calculate the free energy difference between the protonated and neutral states of amines in aqueous solution with inexpensive computational cost. The calculated pK values were in satisfactory agreement with the experimental values, the mean absolute deviation being only 0.09 pK units for 34 amines commonly used in CO scrubbing. Such superior reproducibility and correlation compared to estimations by static quantum mechanical calculations highlight the significant effect of dynamical proton transfer processes in explicit solvent molecules for the improvement of the estimation accuracy.

Dcdftbmd: Divide‐and‐Conquer Density Functional Tight‐Binding Program for Huge‐System Quantum Mechanical Molecular Dynamics Simulations

“…The DFTB‐based metadynamics simulation is useful for the sampling of rare events, in particular the study related with chemical reactions . Extending to the DC‐DFTB‐based metadynamics simulation enables to treat model system, which is computationally demanding even at the DFTB level.…”

“…The currently implemented CVs are geometric quantities and presented in Supporting Information. The applications of DFTB-based metadynamics are recently growing, [57,[124][125][126][127] yet their investigated system size has been less than a few hundreds of atoms. The combination with the DC method may be feasible to analyze large complex systems as demonstrated in simulation example section.…”

“…The benchmark calculations showed that simulation of one MD step for water system consisting of a few millions of atoms is completed within minutes using more than one hundred thousands of cores . The developed program has acquired robustness to the reactive system by means of grid box type fragments and enabled QM‐based MD simulations for systems consisting of from hundreds to thousands of atoms routinely when using laboratory workstation and/or moderate computer resources …”

“…[52] The developed program has acquired robustness to the reactive system by means of grid box type fragments and enabled QM-based MD simulations for systems consisting of from hundreds to thousands of atoms routinely when using laboratory workstation and/or moderate computer resources. [53][54][55][56][57][58][59][60][61] Although the parallelized DC-DFTB calculation has bridged the gap of system size existing between QM-based and classical MD simulations, further integrating advanced extensions into the program is necessary to allow the user to facilitate his or her theoretical analysis beyond the straightforward MD simulation under the plain DC-DFTB potential energy surfaces (PES). For example, timescale of DC-DFTB-based MD simulation is typically limited within nanoseconds, which makes it difficult to study chemical reactions with high energy barrier and to sample slow motion events including protein folding and arrangement of molecular aggregates.…”

Development of Divide‐and‐Conquer Density‐Functional Tight‐Binding Method for Theoretical Research on Li‐Ion Battery

“…Since the first development of the DFTB method, it was successfully used for simulating the systems containing up to a thousand of atoms in wide range of physical and chemical science disciplines, i. e. biomolecules, structural and dynamics of proton in various water systems,,,,, carbon capture and storage, and diffusion phenomenon in super‐concentrated sodium battery . For a larger system containing more than one thousand atoms, the DC‐DFTB method was employed ,,,.…”