Improved Density Functionals for Water

Dahlke, Erin E.; Truhlar, Donald G.

doi:10.1021/jp052436c

Cited by 110 publications

(148 citation statements)

References 79 publications

(78 reference statements)

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“…In previous work 50 we have tested the ability of the pairwise additive approximation to reproduce full density functional calculations of binding energies of small water clusters ranging in size from trimer to pentamer. The database used in that work consists of a set of eight trimers, six tetramers, and a pentamer; the structures are taken from Monte Carlo and molecular mechanics simulations of bulk water and ice, as well as from gas-phase optimizations.…”

Section: Resultsmentioning

confidence: 99%

“…Unfortunately, while the pairwise additive approximation may give qualitatively correct results it does not give good quantative results, even for small clusters with highly accurate pair potentials. 50 While the inclusion of the three-body terms helps to improve quantitative accuracy, 51 the results may still be insufficiently accurate for systems in which many-body effects play an important role, such as water clusters. 52 As a result of these shortcomings, some workers have tried to modify the pairwise and three-body approximations by adding additional terms to the monomer, dimer, or trimer Hamiltonian that account for the electrostatic field of the other atoms in the system.…”

Section: Introductionmentioning

confidence: 99%

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Electrostatically Embedded Many-Body Expansion for Large Systems, with Applications to Water Clusters

Dahlke

Truhlar

2006

J. Chem. Theory Comput.

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284

347

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Abstract:The use of background molecular charge to incorporate environmental effects on a molecule or active site is widely employed in quantum chemistry. In the present article we employ this practice in conjunction with many-body expansions. In particular, we present electrostatically embedded two-body and three-body expansions for calculating the energies of molecular clusters. The system is divided into fragments, and dimers or trimers of fragments are calculated in a field of point charges representing the electrostatic potential of the other fragments. We find that including environmental point charges can lower the errors in the electrostatically embedded pairwise additive (EE-PA) energies for a series of water clusters by as much as a factor of ten when compared to the traditional pairwise additive approximation, and that for the electrostatically embedded three-body (EE-3B) method the average mean unsigned error over nine different levels of theory for a set of six tetramers and one pentamer is only 0.05 kcal/mol, which is only 0.4% of the mean unsigned net interaction energy. We also test the accuracy of the EE-PA and EE-3B methods for a cluster of 21 water molecules and find that the errors relative to a full MP2/aug´-cc-pVTZ calculation to be only 2.97 and 0.38 kcal/mol, respectively, which are only 1.5% and 0.2% respectively of the net interaction energy. This method offers the advantage over some other fragment-based methods that it does not use an iterative method to determine the charges, and thus provides substantial savings for large clusters. The method is convenient to adapt to a variety of electronic structure methods and program packages, it has N 2 or N 3 computational scaling for large systems (where N is the number of fragments), and it is easily converted to an O(N) method, and its linearity allows for convenient analytic gradients.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electrostatically Embedded Many-Body Expansion for Large Systems, with Applications to Water Clusters

Dahlke

Truhlar

2006

J. Chem. Theory Comput.

Self Cite

284

347

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“…The type and hierarchy of the interactions (electrostatic, inductive, hydrogen bonding, and dispersive interactions) responsible for driving OH − to the interface are not fully resolved by current density functionals (7,44,(49)(50)(51)(52). balance each other on the aerial side of water, the point of zero charge, is pH PZC ∼3.…”

Section: Quantum-mechanical Calculationsmentioning

confidence: 99%

Brønsted basicity of the air–water interface

Mishra

Enami

Nielsen

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

172

203

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Differences in the extent of protonation of functional groups lying on either side of water-hydrophobe interfaces are deemed essential to enzymatic catalysis, molecular recognition, bioenergetic transduction, and atmospheric aerosol-gas exchanges. The sign and range of such differences, however, remain conjectural. Herein we report experiments showing that gaseous carboxylic acids RCOOH(g) begin to deprotonate on the surface of water significantly more acidic than that supporting the dissociation of dissolved acids RCOOH(aq). Thermodynamic analysis indicates that > 6 H 2 O molecules must participate in the deprotonation of RCOOH(g) on water, but quantum mechanical calculations on a model air-water interface predict that such event is hindered by a significant kinetic barrier unless OH − ions are present therein. Thus, by detecting RCOO − we demonstrate the presence of OH − on the aerial side of on pH > 2 water exposed to RCOOH(g). Furthermore, because in similar experiments the base (Me) 3 N(g) is protonated only on pH < 4 water, we infer that the outer surface of water is Brønsted neutral at pH ∼3 (rather than at pH 7 as bulk water), a value that matches the isoelectric point of bubbles and oil droplets in independent electrophoretic experiments. The OH − densities sensed by RCOOH(g) on the aerial surface of water, however, are considerably smaller than those at the (>1 nm) deeper shear planes probed in electrophoresis, thereby implying the existence of OH − gradients in the interfacial region. This fact could account for the weak OH − signals detected by surface-specific spectroscopies.gas-liquid reactions | surface potential | water surface acidity | interfacial proton transfer A cid-base chemistry at aqueous interfaces lies at the heart of major processes in chemistry and biology. Changes in the degree of dissociation of the acidic/basic residues upon translocation between aqueous and hydrophobic microenvironments orchestrate enzyme catalysis (1), drive proton/electron transport across biomembranes (2, 3), and mediate molecular recognition and self-assembly phenomena (4-6). Despite its importance, the characterization of acid-base chemistry at aqueous interfaces remains fraught with uncertainties (7-11). Basic questions linger about the thickness of interfacial layers (12), how acidity changes through the interfacial region (13), and the mechanistic differences between proton transfer (PT) across interfacial (IF) versus in bulk (B) water (10,14). Because aqueous surfaces are usually charged relative to the bulk liquid (15), the thermodynamic requirement of uniform electrochemical activity throughout (including the interfacial regions) implies that the chemical activity of protons (pH) in IF could be different from that in the B liquid. Reduced hydration of ionic species at the interface could force acids and bases toward their undissociated forms (16).These fundamental issues have been extensively investigated via electrostatic (17) and electrokinetic experiments (11), surface tension studies and analysis (1...

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“…For example, the PBE value for H 2 O dimer interactions is about 0.02 eV higher than the benchmark number from high level quantum chemistry calculations. 38 It should be noted that the DFT-PBE error could be as high as 0.05 eV for highly nonlinear H bonds. 39 However, DFT at the generalized gradient approximation ͑GGA͒ level is not suitable for dispersion interactions, which may play a more important role for larger complex structures.…”

Section: Experimental and Computational Detailsmentioning

confidence: 99%

Low-temperature adsorption of H2S on Ag(111)

Russell

Liu

Kawai

et al. 2010

The Journal of Chemical Physics

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H 2 S forms a rich variety of structures on Ag(111) at low temperature and submonolayer coverage. The molecules decorate step edges, exist as isolated entities on terraces, and aggregate into clusters and islands, under various conditions. One type of island exhibits a (×)R25.3° unit cell. Typically, molecules in the clusters and islands are separated by about 0.4 nm, the same as the S-S separation in crystalline H 2 S. Density functional theory indicates that hydrogen-bonded clusters contain two types of molecules. One is very similar to an isolated adsorbed H 2 S molecule, with both S-H bonds nearly parallel to the surface. The other has a S-H bond pointed toward the surface. The potential energy surface for adsorption and diffusion is very smooth. KeywordsAmes Laboratory, adsorption, density functional theory, diffusion, hydrogen bonds, intermolecular forces, island structure, molecular clusters, potential energy surfaces, silver, sulphur compounds H 2 S forms a rich variety of structures on Ag͑111͒ at low temperature and submonolayer coverage. The molecules decorate step edges, exist as isolated entities on terraces, and aggregate into clusters and islands, under various conditions. One type of island exhibits a ͑ ͱ 37ϫ ͱ 37͒R25.3°unit cell.Typically, molecules in the clusters and islands are separated by about 0.4 nm, the same as the S-S separation in crystalline H 2 S. Density functional theory indicates that hydrogen-bonded clusters contain two types of molecules. One is very similar to an isolated adsorbed H 2 S molecule, with both S-H bonds nearly parallel to the surface. The other has a S-H bond pointed toward the surface. The potential energy surface for adsorption and diffusion is very smooth.

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Improved Density Functionals for Water

Cited by 110 publications

References 79 publications

Electrostatically Embedded Many-Body Expansion for Large Systems, with Applications to Water Clusters

Electrostatically Embedded Many-Body Expansion for Large Systems, with Applications to Water Clusters

Brønsted basicity of the air–water interface

Low-temperature adsorption of H2S on Ag(111)

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