i-TTM Model for Ab Initio-Based Ion–Water Interaction Potentials. 1. Halide–Water Potential Energy Functions (original) (raw)
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Physical chemistry chemical physics : PCCP, 2016
A new set of i-TTM potential energy functions describing the interactions between alkali metal ions and water molecules is reported. Following our previous study on halide ion-water interactions [J. Phys. Chem. B, 2016, 120, 1822], the new i-TTM potentials are derived from fits to CCSD(T) reference energies and, by construction, are compatible with the MB-pol many-body potential, which has been shown to accurately predict the properties of water from the gas to the condensed phase. Within the i-TTM formalism, two-body repulsion, electrostatic, and dispersion energies are treated explicitly, while many-body effects are represented by classical induction. The accuracy of the new i-TTM potentials is assessed through extensive comparisons with results obtained from different ab initio methods, including CCSD(T), CCSD(T)-F12b, DF-MP2, and several DFT models, as well as from polarizable force fields for M(+)(H2O)n clusters with M(+) = Li(+), Na(+), K(+), Rb(+), and Cs(+), and n = 1-4.
Journal of chemical theory and computation, 2016
Despite recent progress, a unified understanding of how ions affect the structure and dynamics of water across different phases remains elusive. Here, we report the development of full-dimensional many-body potential energy functions, called MB-nrg (Many-Body-energy), for molecular simulations of halide ion-water systems from the gas phase to the condensed phase. The MB-nrg potentials are derived entirely from "first-principles" calculations carried out at the F12 explicitly correlated coupled-cluster level including single, double, and perturbative triple excitations, CCSD(T)-F12, in the complete basis set limit. Building upon the functional form of the MB-pol water potential, the MB-nrg potentials are expressed through the many-body expansion of the total energy in terms of explicit contributions representing one-body, two-body, and three-body interactions, with all higher-order contributions being described by classical induction. The specific focus of this study is on ...
The Journal of Chemical Physics, 2018
Full-dimensional vibrational spectra are calculated for both X − (H 2 O) and X − (D 2 O) dimers (X = F, Cl, Br, I) at the quantum-mechanical level. The calculations are carried out on two sets of recently developed potential energy functions (PEFs), namely TTM-nrg and MB-nrg, using the symmetry-adapted Lanczos algorithm with a product basis set including all six vibrational coordinates. Although both TTM-nrg and MB-nrg PEFs are derived from CCSD(T)-F12 data obtained in the complete basis set limit, they differ in how many-body effects are represented at short range. Specifically, while both models describe long-range interactions through the combination of two-body dispersion and many-body classical electrostatics, the relatively simple Born-Mayer functions employed in the TTM-nrg PEFs to represent short-range interactions are replaced in the MB-nrg PEFs by permutationally invariant polynomials to achieve chemical accuracy. For all dimers, the MB-nrg vibrational spectra are in close agreement with the available experimental data, correctly reproducing anharmonic and nuclear quantum effects. In contrast, the vibrational frequencies calculated with the TTM-nrg PEFs exhibit significant deviations from the experimental values. The comparison between the TTM-nrg and MB-nrg results thus reinforces the notion that an accurate representation of both short-range interactions associated with electron density overlap and long-range many-body electrostatic interactions is necessary for a correct description of hydration phenomena at the molecular level.
The Journal of Physical Chemistry B, 1997
Ab initio calculations were performed on M(H 2 O) n systems, M being Li + , Na + , K + , Be 2+ , Mg 2+ , or Ca 2+ , with n ) 1, 2, 4, or 6. For the most hydrated systems, parameters for the effective Lennard-Jones interaction between the cation and the water molecules were determined, so as to reproduce ab initio results. In order to compare our results to those obtained previously by J. A°qvist with a purely empirical approach, waterwater interactions were assumed to be given by the TIP3P model. Different forms for the effective two-body interaction potential were tested. The best fits of ab initio data were obtained with a smooth r -7 repulsive and a classical r -4 attractive term, in addition to standard Coulombic interactions. Though better fits were obtained for alkaline cations than for alkaline-earth ones, only Be 2+ obviously requires a more complicated form of the potential energy function. The corresponding parameters were tested with molecular dynamics simulations of cations in water solutions and with hydration free energy difference calculations, using the thermodynamic perturbation approach. Radial distribution functions consistent with experimental data were obtained for all cations. Free energy differences are obviously much more challenging. The most accurately reproduced value is the difference between the hydration free energies of Na + and K + . This result is likely to be significant since effective interaction energies between Na + or K + and water molecules as obtained in A°qvist's and in the present work are found to be very similar, despite the fact that the corresponding sets of parameters were determined with completely different approaches.
Molecular Theories and Simulation of Ions and Polar Molecules in Water
The Journal of Physical Chemistry A, 1998
Recent developments in molecular theories and simulation of ions and polar molecules in water are reviewed. The hydration of imidazole and imidazolium solutes is used to exemplify the theoretical issues. The treatment of long-ranged electrostatic interactions in simulations is discussed extensively. It is argued that the Ewald approach is an easy way to get correct hydration free energies in the thermodynamic limit from molecular calculations; and that molecular simulations with Ewald interactions and periodic boundary conditions can also be more efficient than many common alternatives. The Ewald treatment permits a conclusive extrapolation to infinite system size. Accurate results for well-defined models have permitted careful testing of simple theories of electrostatic hydration free energies, such as dielectric continuum models. The picture that emerges from such testing is that the most prominent failings of the simplest theories are associated with solvent proton conformations that lead to non-gaussian fluctuations of electrostatic potentials. Thus, the most favorable cases for second-order perturbation theories are monoatomic positive ions. For polar and anionic solutes, continuum or gaussian theories are less accurate. The appreciation of the specific deficiencies of those simple models have led to new concepts, multistate gaussian and quasi-chemical theories, that address the cases for which the simpler theories fail. It is argued that, relative to direct dielectric continuum treatments, the quasi-chemical theories provide a better theoretical organization for the computational study of the electronic structure of solution species.
Polarizable Intermolecular Potentials for Water and Benzene Interacting with Halide and Metal Ions
Journal of Chemical Theory and Computation, 2009
A complete derivation of polarizable intermolecular potentials based on high-level, gas-phase quantum-mechanical calculations is proposed. The importance of appreciable accuracy together with inherent simplicity represents a significant endeavor when enhancement of existing force fields for biological systems is sought. Toward this end, symmetry-adapted perturbation theory (SAPT) can provide an expansion of the total interaction energy into physically meaningful e.g. electrostatic, induction and van der Waals terms. Each contribution can be readily compared with its counterpart in classical force fields. Since the complexity of the different intermolecular terms cannot be fully embraced using a minimalist description, it is necessary to resort to polyvalent expressions capable of encapsulating overlooked contributions from the quantum-mechanical expansion. This choice results in consistent force field components that reflect the underlying physical principles of the phenomena. This simplified potential energy function is detailed and definitive guidelines are drawn. As a proof of concept, the methodology is illustrated through a series of test cases that include the interaction of water and benzene with halide and metal ions. In each case considered, the total energy is reproduced accurately over a range of biologically relevant distances.
Polarizable Water Potential Derived from a Model Electron Density
Journal of Chemical Theory and Computation, 2021
A new empirical potential for efficient, large scale molecular dynamics simulation of water is presented. The HIPPO (Hydrogen-like Intermolecular Polarizable POtential) force field is based upon the model electron density of a hydrogen-like atom. This framework is used to derive and parametrize individual terms describing charge penetration damped permanent electrostatics, damped polarization, charge transfer, anisotropic Pauli repulsion, and damped dispersion interactions. Initial parameter values were fit to Symmetry Adapted Perturbation Theory (SAPT) energy components for ten water dimer configurations, as well as the radial and angular dependence of the canonical dimer. The SAPTbased parameters were then systematically refined to extend the treatment to water bulk phases. The final HIPPO water model provides a balanced representation of a wide variety of properties of gas phase clusters, liquid water, and ice polymorphs, across a range of temperatures and pressures. This water potential yields a rationalization of water structure, dynamics, and thermodynamics explicitly correlated with an ab initio energy decomposition, while providing a level of accuracy comparable or superior to previous polarizable atomic multipole force fields. The HIPPO water model serves as a cornerstone around which similarly detailed physicsbased models can be developed for additional molecular species.
Intermolecular Dynamics of Water: Suitability of Reactive Interatomic Potential
The Journal of Physical Chemistry B
Review of interatomic potentials TIP4P/2005f TIP4P exible model 1 (TIP4P/2005f) is extension of TIP4P model 2 (TIP4P/2005) with relaxation incorporated for intramolecular degree of freedom. TIP4P/2005f model consists of 4-point interaction site, H-O-H along with M site lying on bisector of H-O-H angle. Here two positive and one negative charges are placed at two hydrogens and at M-site respectively. Only oxygen is considered as Lennard-Jones interaction site. Hence LJ interaction between two water molecule is dened as