Anisotropic structure and dynamics of the solvation shell of a benzene solute in liquid water from ab initio molecular dynamics simulations (original) (raw)
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Dispersion-Corrected Density Functional Theory for Aromatic Interactions in Complex Systems
Accounts of Chemical Research, 2013
Aromatic interactions play a key role in many chemical and biological systems. However, even if very simple models are chosen, the systems of interest are often too large to be handled with standard wave function theory (WFT). Although density functional theory (DFT) can easily treat systems of more than 200 atoms, standard semilocal (hybrid) density functional approximations fail to describe the London dispersion energy, a factor that is essential for accurate predictions of inter- and intramolecular noncovalent interactions. Therefore dispersion-corrected DFT provides a unique tool for the investigation and analysis of a wide range of complex aromatic systems. In this Account, we start with an analysis of the noncovalent interactions in simple model dimers of hexafluorobenzene (HFB) and benzene, with a focus on electrostatic and dispersion interactions. The minima for the parallel-displaced dimers of HFB/HFB and HFB/benzene can only be explained when taking into account all contributions to the interaction energy and not by electrostatics alone. By comparison of saturated and aromatic model complexes, we show that increased dispersion coefficients for sp(2)-hybridized carbon atoms play a major role in aromatic stacking. Modern dispersion-corrected DFT yields accurate results (about 5-10% error for the dimerization energy) for the relatively large porphyrin and coronene dimers, systems for which WFT can provide accurate reference data only with huge computational effort. In this example, it is also demonstrated that new nonlocal, density-dependent dispersion corrections and atom pairwise schemes mutually agree with each other. The dispersion energy is also important for the complex inter- and intramolecular interactions that arise in the molecular crystals of aromatic molecules. In studies of hexahelicene, dispersion-corrected DFT yields "the right answer for the right reason". By comparison, standard DFT calculations reproduce intramolecular distances quite accurately in single-molecule calculations while inter- and intramolecular distances become too large when dispersion-uncorrected solid-state calculations are carried out. Dispersion-corrected DFT can fix this problem, and these results are in excellent agreement with experimental structure and energetic (sublimation) data. Uncorrected treatments do not even yield a bound crystal state. Finally, we present calculations for the formation of a cationic, quadruply charged dimer of a porphyrin derivative, a case where dispersion is required in order to overcome strong electrostatic repulsion. A combination of dispersion-corrected DFT with an adequate continuum solvation model can accurately reproduce experimental free association enthalpies in solution. As in the previous examples, consideration of the electrostatic interactions alone does not provide a qualitatively or quantitatively correct picture of the interactions of this complex.
Quantum Monte Carlo Study of Water Dimer Binding Energy and Halogen–π Interactions
The Journal of Physical Chemistry A, 2019
Halogen-π systems are involved with competition between halogen bonding and πinteraction. Using the diffusion quantum Monte Carlo (DMC) method, we compare the interaction of benzene with diatomic halogens (X 2 : Cl 2 /Br 2) with the typical hydrogen bonding in the water dimer, taking into account explicit correlations of up to three bodies. The benzene Cl 2 /Br 2 binding energies (13.07 ± 0.42 / 16.62 ± 0.02 kJ/mol) attributed to both halogen bonding and dispersion are smaller than but comparable to the typical hydrogen bonding in the water dimer binding energy (20.88 ± 0.27 kJ/mol). All the above values are in good agreement with those from the coupled-cluster with single, double, and non-iterative triple excitations (CCSD(T)) results at the complete basis set limit (benzene Cl 2 /Br 2 : 12.78 / 16.17 kJ/mol; water dimer: 21.0 kJ/mol).
The Journal of Chemical Physics, 2009
This paper presents an approach for obtaining accurate interaction energies at the DFT level for systems where dispersion interactions are important. This approach combines Becke and Johnson's [J. Chem. Phys. 127, 154108 (2007)] method for the evaluation of dispersion energy corrections and a Hirshfeld method for partitioning of molecular polarizability tensors into atomic contributions. Due to the availability of atomic polarizability tensors, the method is extended to incorporate anisotropic contributions, which prove to be important for complexes of lower symmetry. The method is validated for a set of eighteen complexes, for which interaction energies were obtained with the B3LYP, PBE and TPSS functionals combined with the aug-cc-pVTZ basis set and compared with the values obtained at CCSD(T) level extrapolated to a complete basis set limit. It is shown that very good quality interaction energies can be obtained by the proposed method for each of the examined functionals, the overall performance of the TPSS functional being the best, which with a slope of 1.00 in the linear regression equation and a constant term of only 0.1 kcal/mol allows to obtain accurate interaction energies without any need of a damping function for complexes close to their exact equilibrium geometry.
Molecular Density Functional Theory of Water
The Journal of Physical Chemistry Letters, 2013
Three-dimensional implementations of liquid-state theories offer an efficient alternative to computer simulations for the atomic-level description of aqueous solutions in complex environments. In this context, we present a (classical) molecular density functional theory (MDFT) of water that is derived from first principles and is based on two classical density fields, a scalar one, the particle density, and a vectorial one, the multipolar polarization density. Its implementation requires as input the partial charge distribution of a water molecule and three measurable bulk properties, namely, the structure factor and the k-dependent longitudinal and transverse dielectric constants. It has to be complemented by a solute−solvent threebody term that reinforces tetrahedral order at short-range. The approach is shown to provide the correct 3-D microscopic solvation profile around various molecular solutes, possibly possessing H-bonding sites, at a computer cost two to three orders of magnitude lower than with explicit simulations.
A Molecular Density Functional Theory of Water
2016
Three dimensional implementations of liquid state theories offer an efficient alternative to computer simulations for the atomic-level description of aqueous solutions in complex environments. In this context, we present a (classical) molecular density functional theory (MDFT) of water that is derived from first principles and is based on two classical density fields, a scalar one, the particle density, and a vectorial one, the multipolar polarization density. Its implementa-tion requires as input the partial charge distribution of a water molecule and three measurable bulk properties, namely the structure factor and the k-dependent lon-gitudinal and transverse dielectric constants. It has to be complemented by a solute-solvent three-body term that reinforces tetrahedral order at short range. The approach is shown to provide the correct three-dimensional microscopic sol-vation profile around various molecular solutes, possibly possessing H-bonding sites, at a computer cost two-three...
Tackling solvent effect by coupling electronic and molecular Density Functional Theory
2020
Solvation effect might have a tremendous influence on chemical reactions. However, precise quantum chemistry calculations are most often done either in vacuum neglecting the role of the solvent or using continuum solvent model ignoring its molecular nature. We propose a new method coupling a quantum description of the solute using electronic density functional theory with a classical grand-canonical treatment of the solvent using molecular density functional theory. Unlike previous work, both densities are minimized self consistently, accounting for mutual polarization of the molecular solvent and the solute. The electrostatic interaction is accounted using the full electron density of the solute rather than fitted point charges. The introduced methodology represents a good compromise between the two main strategies to tackle solvation effect in quantum calculation. It is computationally more effective than a direct quantum-mechanics/molecular mechanics coupling, requiring the explo...
Benzene water interaction: From gaseous dimers to solvated aggregates
Chemical Physics, 2012
A recent formulation of intermolecular interactions has been adopted to describe the C 6 H 6-H 2 O system by combining a few interaction components. The pure electrostatic contribution accounts for the quadrupole-dipole interaction and the remaining ones are represented as a combination of effective potential terms, containing one non directly transferable and two transferable parameters. The first one introduces a high flexibility to the potential function and the last ones, well depth and distance at the minimum associated to the different interaction pairs, have a defined physical meaning and are derived by exploiting the decomposability of molecular polarizabilities (without performing any fit). For a given decomposition, the transferable parameters are assumed to have an universal character and, thanks to the flexibility of the function, they may be used to describe the same system in different environments, even when the charge distribution varies. Predicted results for the C 6 H 6-H 2 O dimer are compared with ab initio calculations. The behavior of benzene solvated by several water molecules is investigated by performing molecular dynamics simulations and the results are relevant to define some basic features of the main solvation shells.
1997
Conventional ab initio and density functional methods with extended basis sets were employed in the study of a path on the water-dimer potential energy surface. The results show that density functional methods do depend strongly on the type of exchange-correlation potential employed, as well as on the quality of the basis sets -similarly to conventional ab initio methodsand on the density of the grid. Gradient-corrected methods behave, as expected, better than uncorrected ones, the Becke-Lee-Yang-Parr (BLYP) potential being the one that gives the best results. However, too large chemical-and hydrogen-bond lengths and absolute energies, as well as too small relative total and correlation energies demonstrate that even BLYP calculations with a relative large basis set are not good as MP2 calculations of the same size. Adiabatically connected functionals (ACM), represented in this work by B3PW91, provide an improvement on the whole surface.
Journal of Computational Chemistry, 2007
Standard density functional theory (DFT) is augmented with a damped empirical dispersion term. The damping function is optimized on a small, well balanced set of 22 van der Waals (vdW) complexes and verified on a validation set of 58 vdW complexes. Both sets contain biologically relevant molecules such as nucleic acid bases. Results are in remarkable agreement with reference high-level wave function data based on the CCSD(T) method. The geometries obtained by full gradient optimization are in very good agreement with the best available theoretical reference. In terms of the standard deviation and average errors, results including the empirical dispersion term are clearly superior to all pure density functionals investigated-B-LYP, B3-LYP, PBE, TPSS, TPSSh, and BH-LYPand even surpass the MP2/cc-pVTZ method. The combination of empirical dispersion with the TPSS functional performs remarkably well. The most critical part of the empirical dispersion approach is the damping function. The damping parameters should be optimized for each density functional/basis set combination separately. To keep the method simple, we optimized mainly a single factor, s R , scaling globally the vdW radii. For good results, a basis set of at least triple-quality is required and diffuse functions are recommended, since the basis set superposition error seriously deteriorates the results. On average, the dispersion contribution to the interaction energy missing in the DFT functionals examined here is about 15 and 100% for the hydrogen-bonded and stacked complexes considered, respectively.