Electron affinity of liquid water

Calculations of charged systems in periodic boundary conditions (PBC) are problematic because there are spurious interactions between the charges in different periodic images that can affect the physical picture. In addition, the intuitive limit of Coulomb interactions decaying to zero as the interacting charges are placed at infinite separation no longer applies, and for example total energies become undefined. Leveraging subsystem density functional theory (also known as density embedding) we define an impurity model that embeds a finite neutral or charged subsystem within an extended (infinite) surrounding subsystem. The combination of the impurity model and a consistent choice of the Coulomb reference provides us with an algorithm for evaluating the ionization potential (IP) in extended systems. We demonstrate our approach in a pilot calculation of the IP of liquid water, based on a configuration from a prior ab initio molecular dynamics (AIMD) simulation of liquid water (Genova et al., J. Chem. Phys. 2016, 144, 234105). The calculations with the impurity model capture the broadening on the ionization energies introduced by the interactions between the water molecules. Furthermore, the calculated average IP value (10.5 eV) compare favorably to experiments (9.9-10.06 eV) and very recent simulations based on the GW approximation (10.55 eV), while at the same time outperforming density embedding calculations carried out with a naïve handling of the electrostatic interactions (about 7 eV). K E Y W O R D S DFT, embedding, periodic boundary conditions, water 1 | INTRODUCTION Atomistic models of extended systems (such as solids and liquids) typically prescribe the use of periodic boundary conditions (PBC). Once PBC are invoked, one has the choice of evaluating Coulomb interactions in real space or in reciprocal space. If real space is chosen, considering r, r 0 2R 3 then the Coulomb kernel is w r, r 0 ð Þ¼ 1 jr− r 0 j hinting that it decays to zero when two charges are far away. Despite the decay feature of the kernel, Coulomb potentials and energies for extended systems involve conditionally convergent integrals [1] -a complication which is dealt with by switching to reciprocal space. From a purely theoretical standpoint, in PBC, distance is not a well-defined quantity [2] and the physical kernel is only the one represented in reciprocal space, w G ð Þ¼ 4π G j j 2 (G 2 R 3 an element of the reciprocal space). Thus, complications arise because when G = 0, as the Coulomb kernel becomes undefined. In Ewald summations, [3] this is dealt with using a two-prongued approach: the short-range interactions are dealt with in real space (using a cut-off function, typically the error function), and the long-range interactions are dealt with in reciprocal space.In practice, however, the kernel singularity at G = 0 is not problematic because, although w(G) is singular for G = 0, the total charge density ρ(G) is zero for G = 0. We note that neutrality of the charge density in each unit cell is the only physical choice in PBC, beca...

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“…However, it generally leads to a term linear in the charge density involving up to quadrupole terms. [5,6,16,[36][37][38]…”

Section: Methods I: Finite Potential Interacting With a Periodic Chargementioning

confidence: 99%

“…Liquid GW B [6] densities are reproduced by the dielectric continuum model for both neutral and cation water molecules. We also note that the polarization densities from the embedding calculation is slightly less symmetric than the COSMO ones and shows features proper of specific moleculeenvironment interactions.…”

Section: Bulk Water and Its Ionization Potentialmentioning

confidence: 99%

Charged‐cell periodic DFT simulations via an impurity model based on density embedding: Application to the ionization potential of liquid water

Tölle

Gomes

Ramos

et al. 2018

Int J of Quantum Chemistry

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“…Among existing many-body PEFs for water, MBpol has been shown to correctly predict the vibration-rotation tunneling spectrum of the water dimer [103], the energetics, quantum equilibria, and infrared spectra of small clusters [104,[106][107][108], the structural, thermodynamic, and dynamical properties of liquid water [105,109], the energetics of different ice phases [110], infrared and Raman spectra of liquid water [111][112][113], the vibrational sum-frequency generation spectrum of the air/water interface [114,115], the infrared and Raman spectra of ice I h [116]. More recently, molecular configurations extracted from classical (MD) and quantum pathintegral molecular dynamics (PIMD) simulations with MB-pol have been used to determine the electronic band gap of liquid water, both in the bulk and at the air/water interface, through many-body perturbation theory electronic structure calculations [117].…”

Section: Many-body Expansion Of the Interaction Energymentioning

confidence: 99%

Chemical Accuracy in Modeling Halide Ion Hydration from Many-Body Representations

Paesani¹,

Bajaj²,

Riera³

2018

Preprint

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<div> <div> <div> <p>Despite the key role that ionic solutions play in several natural and industrial processes, a unified, molecular-level understanding of how ions affect the structure and dynamics of water across different phases remains elusive. In this context, computer simulations can provide new insights that are difficult, if not impossible, to obtain by other means. However, the predictive power of a computer simulation directly depends on the level of “realism” that is used to represent the underlying molecular interactions. Here, we report a systematic analysis of many-body effects in halide-water clusters and demonstrate that the recently developed MB-nrg full-dimensional many-body potential energy functions achieve high accuracy by quantitatively reproducing the individual terms of the many-body expansion of the interaction energy, thus opening the door to realistic computer simulations of ionic solutions. </p> </div> </div> </div>

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“…[82,119] More recently, path-integral molecular dynamics simulations have been combined with MBPT to probe the electronic structures of liquid water and of its surface. [120] In this study, the molecular dynamics simulations were carried out with the many-body MB-pol potential energy function with the inclusion of NQEs, which accurately describes the structural properties of water in gaseous and condensed phases. [121][122][123] In addition, the electronic structures were calculated at the G 0 W 0 level of theory, starting from the wavefunctions determined with the DDH hybrid functionals.…”

Section: Electronic Structuresmentioning

confidence: 99%

“…The energy levels were computed using the G 0 W 0 approach, starting from the DDH functionals; the range given above (thick bars) corresponds to results obtained with range-separated and self-consistent hybrid density functionals. Reprinted by permission from Macmillan Publishers Ltd: Nature Communications, Gaiduk et al, [120] copyright 2018 FIGURE 6 The ionization potentials (IPs) of 16 solvated anions: Comparison between liquid-jet experimental data and DFT calculations with the self-consistent DDH functional. From Pham et al, [82] reprinted with permission from AAAS Solvation and diffusion of Li + and its counter ion PF − 6 have been investigated for several organic solvents, including ethylene carbonate (EC), ethyl methyl carbonate (EMC), and a mixture of EC and EMC.…”

Section: Organic Electrolytesmentioning

confidence: 99%

Ab initio simulations of liquid electrolytes for energy conversion and storage

Pham

2018

Int J of Quantum Chemistry

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Understanding physicochemical properties of liquid electrolytes is essential for predicting and optimizing device performance for a wide variety of emerging energy technologies, including photoelectrochemical water splitting, supercapacitors, and batteries. In this work, we review recent progress and open challenges in predicting structural, dynamical, and electronic properties of the liquids using first-principles approaches. We briefly summarize the basic concepts of first-principles molecular dynamics (FPMD), and we discuss how FPMD methods have enriched our understanding of a number of liquids, including aqueous solutions, organic electrolytes and ionic liquids. We also discuss technical challenges in extending FPMD simulations to the study of liquid electrolytes in more complex environments, including the interface between electrolytes and electrodes, which is a key component in many energy storage and conversion systems. K E Y W O R D S energy conversion and storage, first-principles simulations, liquid electrolytes 1 | INTRODUCTIONLiquid electrolytes are essential components in a wide variety of emerging energy and environmental technologies, including hydrogen production through solar-water-splitting, [1,2] supercapacitors, [3][4][5] ion batteries, [6][7][8] and ion-selective membranes. [9][10][11] Within these devices, a large number of liquids have been explored, ranging from aqueous solutions and ionic liquids to organic, redox-type, and solid-state electrolytes. At the same time, continuing progress has been made during the past several decades in the development of novel liquids. For example, recent studies show that the use of highly concentrated aqueous electrolytes could open new opportunities for the design of high-voltage aqueous lithium-ion batteries while also significantly improving battery safety. [12,13] For several energy storage and conversion systems, the understanding of structure, dynamics, and electronic properties of liquid electrolytes is essential for predicting and optimizing device performance. For example, desolvation of ions in sub-nanometer carbon electrodes is known to lead to improved capacitive performance. [14][15][16] Controlling transport of the lithium ion in organic electrolytes and at the interface with the graphite anode is key to the development of next-generation lithium ion batteries. [17][18][19][20] Tailoring the electronic structures of aqueous solutions for facilitated charge transfer at semiconductor/water interfaces in photoelectrochemical cells is critical for improving the efficiency of water-splitting reactions for hydrogen production. [21,22] Last but not least, understanding the electronic properties of liquid electrolytes is one of the prerequisites for manipulating the electrochemical stability of electrode-electrolyte interfaces in ion batteries and supercapacitors. [5,23] Structural, dynamical, and electronic properties of liquid electrolytes are often intertwined. For example, it is now widely accepted that the solvation structure of ions in liquid...

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Electron affinity of liquid water

Cited by 150 publications

References 68 publications

Charged‐cell periodic DFT simulations via an impurity model based on density embedding: Application to the ionization potential of liquid water

Charged‐cell periodic DFT simulations via an impurity model based on density embedding: Application to the ionization potential of liquid water

Chemical Accuracy in Modeling Halide Ion Hydration from Many-Body Representations

Ab initio simulations of liquid electrolytes for energy conversion and storage

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