Excited states of OH-(H2O)n clusters for n = 1–4: An ab initio study

Hoffman, G. J.; Gurunathan, Pradeep Kumar; Francisco, Joseph S.; Slipchenko, Lyudmila V.

doi:10.1063/1.4894772

“…67 Theoretical studies of the spectroscopy of the hydrated OH radical have so far been limited to gas-phase cluster studies. 29,61,[68][69][70] Excited states of the binary OH(H 2 O) complex have been reported using equation-of-motion coupled-cluster (EOM-CC) calculations including connected triples (EOM-CCSDT), 29,61 and small clusters OH(H 2 O) n have also been studied using EOM-CCSD, up to n = 7. 68,70 Excited states of a single OH(H 2 O) 16 cluster have been reported using time-dependent (TD-) DFT.…”

Section: Introductionmentioning

confidence: 99%

“…29,61,[68][69][70] Excited states of the binary OH(H 2 O) complex have been reported using equation-of-motion coupled-cluster (EOM-CC) calculations including connected triples (EOM-CCSDT), 29,61 and small clusters OH(H 2 O) n have also been studied using EOM-CCSD, up to n = 7. 68,70 Excited states of a single OH(H 2 O) 16 cluster have been reported using time-dependent (TD-) DFT. 68 Each of these studies confirms the existence of a H 2 O → OH transition whose intensity is sensitive to orbital overlap, 68 and which is suggested to be responsible for the aqueous-phase absorption at 230 nm.…”

Section: Introductionmentioning

confidence: 99%

Role of hemibonding in the structure and ultraviolet spectroscopy of the aqueous hydroxyl radical

Rana

¹

,

Herbert

²

2020

Phys. Chem. Chem. Phys.

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“…67 Theoretical studies of the spectroscopy of the hydrated OH radical have so far been limited to gas-phase cluster studies. 29,61,[68][69][70] Excited states of the binary OH(H 2 O) complex have been reported using equation-of-motion coupled-cluster (EOM-CC) calculations including connected triples (EOM-CCSDT), 29,61 and small clusters OH(H 2 O) n have also been studied using EOM-CCSD, up to n = 7. 68,70 Excited states of a single OH(H 2 O) 16 cluster have been reported using time-dependent (TD-) DFT.…”

Section: Introductionmentioning

confidence: 99%

“…29,61,[68][69][70] Excited states of the binary OH(H 2 O) complex have been reported using equation-of-motion coupled-cluster (EOM-CC) calculations including connected triples (EOM-CCSDT), 29,61 and small clusters OH(H 2 O) n have also been studied using EOM-CCSD, up to n = 7. 68,70 Excited states of a single OH(H 2 O) 16 cluster have been reported using time-dependent (TD-) DFT. 68 Each of these studies confirms the existence of a H 2 O → OH transition whose intensity is sensitive to orbital overlap, 68 and which is suggested to be responsible for the aqueous-phase absorption at 230 nm.…”

Section: Introductionmentioning

confidence: 99%

Role of Hemibonding in the Structure and Ultraviolet Spectroscopy of the Aqueous Hydroxyl Radical

Rana

¹

,

Herbert

²

2020

Preprint

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The presence of a hemibond in the local solvation structure of the aqueous hydroxyl radical has long been debated, as its appearance in ab initio simulations based on density functional theory is sensitive to self-interaction error (favoring a two-center, three-electron hemibond) but also to finite-size effects. Simulations reported here use a mixed quantum mechanics/molecular mechanics (QM/MM) framework in a very large periodic simulation cell, in order to avoid finite-size artifacts and to facilitate testing of various density functionals, in order to probe the effects of delocalization error. The preponderance of hemibonded structures predicted by generalized gradient approximations persists in simulations using the hybrid functionals B3LYP and PBE0, but is reduced to a minor population if the fraction of exact exchange is increased significantly. The hemibonded population is also small in simulations employing the long-range corrected functional LRC-wPBE. Electronic spectra are computed using time-dependent density functional theory, and from these calculations emerges a consensus picture in which hemibonded configurations play an outsized role in the absorption spectrum, even when present as a minority species. An intense 1b2 (H2O) --> 2p (OH) charge-transfer transition in hemibonded configuration of the radical proves to be responsible for an absorption feature at 230~nm that is strongly shifted with respect to the gas-phase absorption at 307 nm, but this intense feature is substantially diminished in aqueous geometries where the hemibond is absent. Although not yet sufficient to quantitatively establish the population of hemibonded OH(aq), these simulations do suggest that its presence is revealed by the strongly shifted ultraviolet absorption spectrum of the aqueous radical.

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“…This coupling is not present in calculation for isolated molecules, and it is responsible for the considerable increase of the computational cost of CC calculations in solution. It is for this reason that most approaches for CC calculations in a polarizable embedding only include the solvent effect in the reference wave function . However, it is desirable to include the solvent response in the correlation energy and density (ie, in the CC amplitudes), and we have devised an approximation to do that without increasing the computational effort.…”

Section: Introductionmentioning

confidence: 99%

Coupled cluster theory with the polarizable continuum model of solvation

Caricato

¹

2018

Int J of Quantum Chemistry

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The environment may significantly affect molecular properties. Thus, it is desirable to account explicitly for these effects on the wave function and its derivatives, especially when the latter are evaluated with accurate methods, such as those belonging to coupled cluster (CC) theory. In this tutorial review, we discuss how to combine CC methods with the polarizable continuum model of solvation (PCM). We describe useful approximations that include the solvent response to the correlation and excited state equations while maintaining the computational cost comparable to in vacuo calculations. Although applied to PCM, the theoretical framework presented in this review is general and can be used with any polarizable embedding model. Representative applications of the CC-PCM method to ground and excited state properties of solvated molecules are presented, and comparisons with experiment, and between the full and approximate schemes are discussed.coupled cluster, PCM, excited states, linear response, state specific 1 | INTRODUCTION Many experimental measurements of chemical processes, from reactivity to spectroscopy, are performed in solution. Theoretical simulations of these phenomena require the use of quantum mechanical (QM) methods to study the electronic behavior. However, these methods involve a considerable computational effort so that the QM region can often only include the solute and possibly a few solvent molecules. Bulk effects cannot be easily reproduced quantum mechanically, and often they do not need to. The main polarization effects of the solvent on the solute electron density can be reproduced with classical solvation models, where the solute-solvent interaction is added to the solute Hamiltonian via an effective one-electron operator. In general, classical solvation models can be divided in two families: implicit and explicit models. The former replace the atomistic description of the solvent with a continuum polarizable medium, and they are computationally very efficient since the solvent response is introduced through a macroscopic quantity of the solvent, that is, the dielectric permittivity. The downside is that direct solute-solvent interactions like hydrogen bonding cannot be described, although continuum models are usually better than the corresponding calculation in vacuo. [1] Conversely, explicit solvation models retain an atomistic representation of the solvent molecules, which are usually treated with a classical force field (MM) that may or may not be polarizable. Explicit models are more realistic, but they require considerable computational effort to ensure proper sampling of the solvent configuration space, which requires the repetition of the QM/MM calculations over many snapshots obtained from a molecular dynamics (MD) simulation. The choice between implicit and explicit models is often based on a compromise between cost and accuracy for the property of interest.This tutorial review is concerned with the interface of coupled cluster (CC) methods, [2,3] among the most accurate but e...

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Excited states of OH-(H2O)n clusters for n = 1–4: An ab initio study

Cited by 20 publications

References 35 publications

Role of hemibonding in the structure and ultraviolet spectroscopy of the aqueous hydroxyl radical

Role of hemibonding in the structure and ultraviolet spectroscopy of the aqueous hydroxyl radical

Role of Hemibonding in the Structure and Ultraviolet Spectroscopy of the Aqueous Hydroxyl Radical

Coupled cluster theory with the polarizable continuum model of solvation

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