Density-functional theory exchange-correlation functionals for hydrogen bonds in water (original) (raw)
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Journal of Chemical Physics, 2008
Second order Møller-Plesset perturbation theory at the complete basis set limit and diffusion quantum Monte Carlo are used to examine several low energy isomers of the water hexamer. Both approaches predict the so-called prism to be the lowest energy isomer, followed by cage, book, and cyclic isomers. The energies of the four isomers are very similar, all being within 10-15 meV/ H 2 O. These reference data are then used to evaluate the performance of several density-functional theory exchange-correlation ͑xc͒ functionals. A subset of the xc functionals tested for smaller water clusters ͓I. Santra et al., J. Chem. Phys. 127, 184104 ͑2007͔͒ has been considered. While certain functionals do a reasonable job at predicting the absolute dissociation energies of the various isomers ͑coming within 10-20 meV/ H 2 O͒, none predict the correct energetic ordering of the four isomers nor does any predict the correct low total energy isomer. All xc functionals tested either predict the book or cyclic isomers to have the largest dissociation energies. A many-body decomposition of the total interaction energies within the hexamers leads to the conclusion that the failure lies in the poor description of van der Waals ͑dispersion͒ forces in the xc functionals considered. It is shown that the addition of an empirical pairwise ͑attractive͒ C 6 R −6 correction to certain functionals allows for an improved energetic ordering of the hexamers. The relevance of these results to density-functional simulations of liquid water is also briefly discussed.
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...
2011
The structure of liquid water at ambient conditions is studied in ab initio molecular dynamics simulations using van der Waals (vdW) density-functional theory, i.e. using the new exchange-correlation functionals optPBE-vdW and vdW-DF2. Inclusion of the more isotropic vdW interactions counteracts highly directional hydrogen-bonds, which are enhanced by standard functionals. This brings about a softening of the microscopic structure of water, as seen from the broadening of angular distribution functions and, in particular, from the much lower and broader first peak in the oxygen-oxygen pair-correlation function (PCF), indicating loss of structure in the outer solvation shells. In combination with softer non-local correlation terms, as in the new parameterization of vdW-DF, inclusion of vdW interactions is shown to shift the balance of resulting structures from open tetrahedral to more close-packed. The resulting O-O PCF shows some resemblance with experiment for high-density water (A. K. Soper and M. A. Ricci, Phys. Rev. Lett., 84:2881, 2000), but not directly with experiment for ambient water. However, an O-O PCF consisting of a linear combination of 70% from vdW-DF2 and 30% from experiment on low-density liquid water reproduces near-quantitatively the experimental O-O PCF for ambient water, indicating consistency with a two-liquid model with fluctuations between high- and low-density regions.
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.
Structure, Dynamics, and Spectral Diffusion of Water from First-Principles Molecular Dynamics
The Journal of Physical Chemistry C, 2014
We have carried out first-principles Born−Oppenheimer molecular dynamics (BOMD) simulations of heavy water using density functional theory in conjunction with either empirical van der Waals (vdW) corrections or semilocal (van der Waals) exchange and correlation functionals. Specifically, gradient-corrected density functionals (BLYP), semiempirical vdW methods (BLYP-D2, BLYP-D3, PBE-D3, revPBE-D3), and vdW density functionals (DRSLL-PBE, DRSLL-optB88) are applied to evaluate their accuracy in describing the hydrogen-bonded network of heavy water. Ab initio trajectories are used to calculate structural and dynamical properties, with special emphasis on vibrational spectral diffusion and hydrogen bond dynamics. Our results show that inclusion of vdW interactions in DFT-GGA significantly affects the structure of liquid water and results in a faster diffusion. The combination of BLYP and revPBE functionals with the semiempirical vdW method of Grimme et al. [J. Chem. Phys. 2010, 132, 154104] and modified B88 functionals with the semilocal correlation functional according to M. Dion et al. [Phys. Rev. Lett. 2004, 92, 246401] provide the best agreement with experiments.
Two exchange-correlation functionals compared for first-principles liquid water
Molecular Simulation, 2005
The first-principles description of liquid water using ab initio molecular dynamics (AIMD) based on Density Functional theory (DFT) has recently been found to require long equilibration times, giving too low diffusivities and a clear over-structuring of the liquid. In the light of these findings we compare here the room-temperature description offered by two different exchange correlation functionals: BLYP, the most popular for liquid water so far, and RPBE, a revision of the widely used PBE. We find for RPBE a less structured liquid with radial distribution functions closer to the experimental ones than the ones of BLYP. The diffusivity obtained with RPBE for heavy water is still 20% lower than the corresponding experimental value, but it represents a substantial improvement on the BLYP value, one order of magnitude lower than experiment. These characteristics and the hydrogen-bond (HB) network imperfection point to an effective temperature ∼3% lower than the actual simulation temperature for the RPBE liquid, as compared with BLYP's ∼17% deviation. The too long O-O average nearest-neighbor distance observed points to an excessively weak HB, possibly compensating more fundamental errors in the DFT description.
The Journal of Chemical Physics, 1996
The structure, dynamical, and electronic properties of liquid water utilizing different hybrid density functionals were tested within the plane wave framework of first-principles molecular dynamics simulations. The computational approach, which employs modified functionals with short-ranged Hartree-Fock exchange, was first tested in calculations of the structural and bonding properties of the water dimer and cyclic water trimer. Liquid water simulations were performed at the state point of 350 K at the experimental density. Simulations included three different hybrid functionals, a meta-functional, four gradient-corrected functionals, and the local density and Hartree-Fock approximations. It is found that hybrid functionals are superior in reproducing the experimental structure and dynamical properties as measured by the radial distribution function and self-diffusion constant when compared to the pure density functionals. The local density and Hartree-Fock approximations show strongly over-and understructured liquids, respectively. Hydrogen bond analysis shows that the hybrid functionals give slightly smaller average numbers of hydrogen bonds than pure density functionals but similar hydrogen bond populations. The average molecular dipole moments in the liquid from the three hybrid functionals are lower than those of the corresponding pure density functionals. † Part of the special issue "Michael L. Klein Festschrift".
Molecular Density Functional Theory for water with liquid-gas coexistence and correct pressure
The solvation of hydrophobic solutes in water is special because liquid and gas are almost at coexistence. In the common hypernetted chain approximation to integral equations, or equivalently in the homogenous reference fluid of molecular density functional theory, coexistence is not taken into account. Hydration structures and energies of nanometer-scale hydrophobic solutes are thus incorrect. In this article, we propose a bridge functional that corrects this thermodynamic inconsistency by introducing a metastable gas phase for the homogeneous solvent. We show how this can be done by a third order expansion of the functional around the bulk liquid density that imposes the right pressure and the correct second order derivatives. Although this theory is not limited to water, we apply it to study hydrophobic solvation in water at room temperature and pressure and compare the results to all-atom simulations.
Molecular dynamics simulation of liquid water between two walls
Chemical Physics Letters, 1983
The structure, dynamical, and electronic properties of liquid water utilizing different hybrid density functionals were tested within the plane wave framework of first-principles molecular dynamics simulations. The computational approach, which employs modified functionals with short-ranged Hartree-Fock exchange, was first tested in calculations of the structural and bonding properties of the water dimer and cyclic water trimer. Liquid water simulations were performed at the state point of 350 K at the experimental density. Simulations included three different hybrid functionals, a meta-functional, four gradient-corrected functionals, and the local density and Hartree-Fock approximations. It is found that hybrid functionals are superior in reproducing the experimental structure and dynamical properties as measured by the radial distribution function and self-diffusion constant when compared to the pure density functionals. The local density and Hartree-Fock approximations show strongly over-and understructured liquids, respectively. Hydrogen bond analysis shows that the hybrid functionals give slightly smaller average numbers of hydrogen bonds than pure density functionals but similar hydrogen bond populations. The average molecular dipole moments in the liquid from the three hybrid functionals are lower than those of the corresponding pure density functionals. † Part of the special issue "Michael L. Klein Festschrift".
Classical density-functional theory for water
2010
Abstract: We introduce a new computationally efficient and accurate classical density-functional theory for water and apply it to hydration of hard spheres and inert gas atoms. We find good agreement with molecular dynamics simulations for the hydration of hard spheres and promising agreement for the solvation of inert gas atoms in water. Finally, we explore the importance of the orientational ambiguity in state-of-the-art continuum theories of water, which are based on the molecular density only.