On the Nature of Halide-Water Interactions: Insights from Many-Body Representations and Density Functional Theory

Abstract

<div> <div> <div> <p>Interaction energies of halide-water dimers, X<sup>-</sup>(H<sub>2</sub>O), and trimers, X<sup>-</sup>(H<sub>2</sub>O)<sub>2</sub>, with X = F, Cl, Br, and I, are investigated using various many-body models and exchange-correlation functionals selected across the hierarchy of density functional theory (DFT) approximations. Analysis of the results obtained with the many-body models demonstrates the need to capture important short-range interactions in the regime of large inter-molecular orbital overlap, such as charge transfer and charge penetration. Failure to reproduce these effects can lead to large deviations relative to reference data calculated at the coupled cluster level of theory. Decompositions of interaction energies carried out with the absolutely localized molecular orbital energy decomposition analysis (ALMO-EDA) method demonstrate that permanent and inductive electrostatic energies are accurately reproduced by all classes of XC functionals (from generalized gradient corrected (GGA) to hybrid and range-separated functionals), while significant variance is found for charge transfer energies predicted by different XC functionals. Since GGA and hybrid XC functionals predict the most and least attractive charge transfer energies, respectively, the large variance is likely due to the delocalization error. In this scenario, the hybrid XC functionals are then expected to provide the most accurate charge transfer energies. The sum of Pauli repulsion and dispersion energies are the most varied among the XC functionals, but it is found that a correspondence between the interaction energy and the ALMO EDA total frozen energy may be used to determine accurate estimates for these contributions. </p> </div> </div> </div>

Data-Driven Many-Body Models for Molecular Fluids: CO2/H2O Mixtures as a Case Study

“…It should be noted that our previous analyses showed that, among the existing functionals, ωB97M-V consistently provides the closer agreement with CCSD(T) reference data for molecular interactions in aqueous systems. 69,71,81,82,111 As expected from the analysis of the correlation plots in Fig. 2 A direct probe of the multidimensional 2B energy landscape is provided by the second virial coefficient,…”

“…1 can be correctly represented in terms of classical many-body polarization as described in Section 2.1. In this context, it should be noted that previous studies of manybody effects in aqueous systems indicated that an explicit representation of 3B energies is necessary to guarantee an accurate description of structural, thermodynamic, dynamical and spectroscopic properties of water 75,[109][110][111] as well as halide-water 69,79,[81][82][83][84][85] and alkali-metal ion-water 71,80,86 interactions in the gas phase and in solution. In particular, it was found that significant error cancellation between different terms of the MBE affects the performance of common force fields and DFT models for water.…”

Data-Driven Many-Body Models with Chemical Accuracy for CH4/H2O Mixtures

“…1 to develop TTM-nrg and MB-nrg PEFs for halide-water, 82,83 alkali-metal ion-water, 84,85 and carbon dioxide-water systems, 86 which have been employed in computer simulations of various aqueous systems. [94][95][96][97][98][99][100][101] While both TTM-nrg and MB-nrg PEFs rely on MB-pol to describe water-water interactions, they differ in the functional forms adopted to represent solute distortions and solute-water interactions. In the TTM-nrg PEF, the CH 4 1B term is represented by a functional form similar to those used in common force fields, which is expressed in Eq.…”

Quantifying the hydration structure of sodium and potassium ions: taking additional steps on Jacob’s Ladder

“…38 Different functionals may describe anion-water and cation-water interactions with signif-icantly different accuracy. 24 GGAs appear to already adequately reproduce the structure of halide ions such as iodide. 61 But the accuracy of SCAN when applied to anions should be tested in future work.…”