Accurate description of the excess charge in water cluster anions is challenging for standard semi-local and (global) hybrid density functional approximations (DFAs). Using the recent unitary invariant implementation of the Perdew-Zunger self-interaction correction (SIC) method using Fermi-Löwdin orbitals, we assess the effect of self-interaction error on the vertical detachment energies of water clusters anions with the local spin density approximation (LSDA), Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation, and the strongly constrained and appropriately normed (SCAN) meta-GGA functionals. Our results show that for the relative energies of isomers with respect to reference CCSD(T) values, the uncorrected SCAN functional has the smallest deviation of 21 meV, better than that for the MP2 method. The performance of SIC-SCAN is comparable to that of MP2 and is better than SIC-LSDA and SIC-PBE, but it reverses the ordering of the two lowest isomers for water hexamer anions. Removing self interaction error (SIE) corrects the tendency of LSDA, PBE, and SCAN to over-bind the extra electron. The vertical detachment energies (VDEs) of water cluster anions, obtained from the total energy differences of corresponding anion and neutral clusters, are significantly improved by removing self-interaction and are better than the hybrid B3LYP functional, but fall short of MP2 accuracy. Removing SIE results in substantial improvement in the position of the eigenvalue of the extra electron. The negative of the highest occupied eigenvalue after SIC provides an excellent approximation to the VDE, especially for SIC-PBE where the mean absolute error with respect to CCSD(T) is only 17 meV, the best among all approximations compared in this work.
Competitive solvation of an ion by two or more solvents is one of the key phenomena determining the identity of our world. Solvation in polar solvents frequently originates from non-additive non-covalent interactions. Pre-parametrized potentials poorly capture these interactions, unless the force field derivation is repeated for every new system. Development cost increases drastically as new chemical species are supplied. This work represents an alternative simulation approach, PM7-MD, by coupling the latest semiempirical parametrization, PM7, with equation-of-motion propagation scheme and tem…
We report a computational study of the structural and energetic properties of water clustersand singly-charged water cluster anions containing from 20 to 573 water molecules. We have used both a classical and a quantum description of the molecular degrees of freedom. Water intra and inter-molecular interactions have been modelled through the SPC/F model, while the water-excess electron interaction has been described via the well-known Turi-Borgis potential. We find that in general the quantum effects of the water degrees of freedom are small, but they do influence the cluster-size at which the…
We have performed dispersion-corrected density-functional transition state calculations on atomic Au- and Pd- catalysis of water conversion to peroxide. The Au- ion is found to be an excellent catalyst; however, atomic Pd- has a higher catalytic effect on the formation of peroxide. The Au^{-}(H2O)2 and Pd^{-}(H2O)2 anion molecular complexes formation in the transition state is identified as the fundamental mechanism for breaking the hydrogen bonding strength during the water catalysis. Our theoretical results provide crucial insight into the mechanism of the atomic Au- and Pd- catalysis in goo…
Core-excitation of water ice releases many different molecules and ions in the gas phase. Studying these desorbed species and the underlying mechanisms can provide useful information on the effects of X-ray irradiation in ice. We report a detailed study of the X-ray induced desorption of a number of neutral, cationic and anionic species from amorphous solid water. We discuss the desorption mechanisms, and the relative contributions of Auger and secondary electrons (X-ray induced Electron Stimulated Desorption) and initial excitation (\rev{direct desorption}) as well as the role of photochemist…
In the course of our investigations of the adsorption of ions to the air-water interface, we previously reported the surprising result that doubly-charged carbonate anions exhibit a stronger surface affinity than do singly-charged bicarbonate anions. In contrast to monovalent, weakly hydrated anions, which generally show enhanced concentrations in the interfacial region, multivalent (and strongly hydrated) anions are expected to show much weaker surface propensity. In the present work, we use resonantly enhanced deep-UV second harmonic generation spectroscopy to measure the Gibbs free energy o…
The adsorption of anions from aqueous solution on the air/water interface controls important heterogeneous chemistry in the atmosphere and is thought to have similar physics to anion adsorption at hydrophobic interfaces more generally. While much theoretical and experimental work over the last 20 years has made clear that the adsorption of large, polarizable anions is thermodynamically favorable, determining the role of polarizability in adsorption has proven surprisingly challenging. Simple physical models make clear that nonpolarizable anions will not adsorb, but trends in adsorption are dif…
Revealing Hydroxide Ion Transport Mechanisms in Commercial Anion-Exchange Membranes at Nano-Scale from Machine-learned Interatomic Potential Simulations
Technische Universität Ilmenau（伊尔梅瑙工业大学）；Fraunhofer-Institut für Keramische Technologien und Systeme IKTS（弗劳恩霍夫陶瓷技术与系统研究所）
We present the results of calculations defining global, three-dimensional representations of the complex-valued potential-energy surfaces of the doublet B1, doublet A1, and doublet B2 metastable states of the water anion that underlie the physical process of dissociative electron attachment to water. The real part of the resonance energies is obtained from configuration-interaction calculations performed in a restricted Hilbert space, while the imaginary part of the energies (the widths) is derived from complex Kohn scattering calculations. A diabatization is performed on the 2A1 and 2B2 surfa…
It is shown that negative ions are ejected from gas-phase water molecules when bombarded with positive ions at keV energies typical of solar-wind velocities. This finding is relevant for studies of planetary and cometary atmospheres, as well as for radiolysis and radiobiology. Emission of both H- and heavier (O- and OH-) anions, with a larger yield for H-, was observed in 6.6-keV 16O+ + H2O collisions. The ex-perimental setup allowed separate identification of anions formed in collisions with many-body dynamics from those created in hard, binary collisions. Most of the ani-ons are emitted with…
We have investigated the electron attachment dynamics of uracil in water using accurate wave-function and QM/MM methods. The initial electron attached state is found to be localized on the water and mixing of electronic and nuclear degrees of freedom leads to the transfer of electron from the water to the uracil. The water molecules around the uracil stabilize the uracil bound anion by creating an extensive hydrogen-bonding network. The presence of the bulk water environment accelerates the rate of electron attachment to uracil and the complete electron transfer from water to the uracil happen…
The fundamental understanding of intermolecular interactions of ionic liquids with water represents a vital extent in predicting ionic liquid properties. Intermolecular or noncovalent interactions were studied for 1,3-dimethyl imidazolium [DMIM]+ cation and nitrate [NO3]- anion with water, employing quantum mechanics (QM) and molecular dynamics (MD) simulations. Extensive electronic structure calculations were performed first for molecular dimers, using various levels of theory and basis sets to pinpoint dimer optimized geometries and estimate binding energies in the gas phase. Many calculatio…
The nature of mobility of ions and water molecules in dilute aqueous solutions of electrolytes (at most fifteen water molecules per ion) is investigated. It is shown that the behavior of the mobility coefficients of water molecules and ions, as well as the self-diffusion coefficients of water molecules, are determined by the radii of their hard shells rather than by the effect of the hydrogen bond network. It is established that the influence of hydration effects on the density of the system and the self-diffusion coefficients of water molecules does not exceed several per cent. Based on micro…
Photoelectron spectroscopy experiments in ionic solutions reveal important electronic structure information, in which the interaction between hydrated ions and water solvent can be inferred. Based on many-body perturbation theory with GW approximation, we theoretically compute the quasiparticle electronic structure of chloride anion solution, which is modeled by path-integral $ab$ $initio$ molecular dynamics simulation by taking account the nuclear quantum effects (NQEs). The electronic levels of hydrated anion as well as water are determined and compared to the recent experimental photoelectr…
Anion hydration is complicated by H-bond donation between neighboring water molecules in addition to H-bond donation to the anion. This situation can lead to competing structures for chemically simple clusters like (H$_2$O)$_n$Cl$^-$ and to anharmonic vibrational motions. Quasi-chemical theory builds from electronic structure treatment of isolated ion-water clusters, partitions the hydration free energy into inner-shell and outer-shell contributions, and provides a general statistical mechanical framework to study complications of anion hydration. The present study exploits dynamics calculatio…
A combined experimental/theoretical approach has been used to investigate the role of water in modifying the microscopic interactions characterizing the optical response of butyl-ammonium nitrate (BAN) water solutions. Raman spectra, dominated by the signal from the protic ionic liquid, were collected as a function of the water content, and the corresponding spatial organization of the ionic couples, as well as their local arrangement with water molecules, was studied exploiting classical molecular dynamics calculations. High quality spectroscopic data, combined with a careful analysis, reveal…
We present a theoretical investigation of the hydrated hydroxide anion clusters OH(H$_{2}$O)$_{n}^{-}$ and of the collisional complexes H-OH(H$_{2}$O)$_{n}^{-}$ and Rb-OH(H$_{2}$O)$_{n}^{-}$ (with n$=1-4$). The MP2 and CCSD(T) methods are used to calculate interaction energies, optimized geometries and vertical detachment energies. Part of the potential energy surfaces are explored with a focus on the autodetachment region. We point out the importance of diffuse functions to correctly describe the latter. We use our results to discuss the different water loss and electronic detachment channels…
We have developed a new basis set family, denoted aug-cc-pVnZ-F12 (or aVnZ-F12 for short), for explicitly correlated calculations. The sets included in this family were constructed by supplementing the corresponding cc-pVnZ-F12 sets with additional diffuse functions on the higher angular momenta (i.e., additional d-h functions on non-hydrogen atoms, and p-g on hydrogen), optimized for the MP2-F12 energy of the relevant atomic anions. The new basis sets have been benchmarked against electron affinities of the first- and second-row atoms, the W4-17 dataset of total atomization energies, the S66 …
We present an unprecedented fluoride-water cyclic cluster of $[F(H_2O)]_4^{4-}$ assembled in a cuboid-shaped molecular box formed by two large macrocycles. Structural characterization reveals that the $[F(H_2O)]_4^{4-}$ is assembled by strong H-bonding interactions (OH...F = 2.684(3) to 2.724(3) Å), where a fluoride anion plays the topological role of a water molecule in the classical cyclic water octamer. The interaction of fluoride was further confirmed by $^{19}$F NMR and $^1$H NMR spectroscopies, indicating the encapsulation of the anionic species within the cavity in solution. High level …
Hydrogen bonds (HBs) play a crucial role in the physicochemical properties of ionic liquids (ILs). At present, HBs between cations and anions (Ca-An) or between cations (Ca-Ca) in ILs have been reported extensively. Here, we provided DFT evidences for the exists of HBs between anions (An-An) in the IL 1-(2-hydroxyethyl)-3-methylimidazolium 4-(2-hydroxyethyl)imidazolide [HEMIm][HEIm]. The thermodynamics stabilities of anionic, cationic, and H2O dimers together with ionic pairs were studied by potential energy scans. The results show that the cation-anion pair is the most stable one, while the H…
As a persistent pollutant, PFOA places a serious threat to natural ecosystems and human health for its global distribution and residual. Currently, adsorption technology is a promising approach for PFOA removal. MOFs become a concerned adsorbent attributing to its special designability and easy modular synthesis. Aiming at improving hydrophobic interactions to absorb PFOA, this study was designed to introduce amino group to decorate Zr-based MOF UiO-66. And subsequently introduced GO to modify UiO-66-NH2 to explore the influence of hydrophobicity on PFOA adsorption removal. Based on the perfor…
We study the surface tension of electrolyte solutions at the air/water and oil/water interfaces. Employing field-theoretical methods and considering short-range interactions of anions with the surface, we expand the Helmholtz free energy to first-order in a loop expansion and calculate the excess surface tension. Our approach is self-consistent and yields an analytical prediction that reunites the Onsager-Samaras pioneering result (which does not agree with experimental data), with the ionic specificity of the Hofmeister series. We obtain analytically the surface-tension dependence on the ioni…
Nitrate is an important pollutant in drinking water worldwide, and a number of methods exist for the removal of nitrate from water including ion exchange and reverse osmosis. However, these approaches suffer from a variety of disadvantages including requirements for supply and disposal of brine used for regeneration in ion exchange and low water recovery ratio for reverse osmosis. Here, we demonstrate the use of high surface area activated carbon electrodes functionalized with moieties having high affinity for adsorption of nitrate from aqueous solution, such as those used in ion exchange. Ads…
Charge injection in terms of anions, cations, electrons, lone pairs, protons, and molecular dipoles by acid,base, salt and organic molecular solvation mediates the O:HO bonding network and properties of the solution through O:H formation, HH fragillization, O:=:O compression, electrostatic polarization, H2O dipolar shielding, and solute/solute interaction
Photoelectron spectra of early $3d-$transition metal dioxide anions, ScO$_{2}^-$, TiO$_{2}^-$, VO$_{2}^-$, CrO$_{2}^-$, MnO$_{2}^-$, are calculated using semilocal and hybrid density functional theory (DFT) and many-body perturbation theory within the $GW$ approximation using one-shot perturbative and eigenvalue self-consistent formalisms. Different levels of theory are compared with each other and with available photoelectron spectra. We show that one-shot $GW$ with a PBE0 starting point ($G_0W_0$@PBE0) consistently provides very good agreement for all experimentally measured binding energies…
The excess electron in liquid ammonia ("ammoniated electron") is commonly viewed as a cavity electron in which the s-type wave function fills the interstitial void between 6-9 ammonia molecules. Here we examine an alternative model in which the ammoniated electron is regarded as a solvent stabilized multimer radical anion, as was originally suggested by Symons [Chem. Soc. Rev. 1976, 5, 337]. In this model, most of the excess electron density resides in the frontier orbitals of N atoms in the ammonia molecules forming the solvation cavity; a fraction of this spin density is transferred to the m…
How is Water released in Hydrogen-Based Metal Oxide Reduction? Unraveling the Kinetic Bottleneck in Sustainable Metal Production
ShanghaiTech University（上海科技大学）；Suzhou National Laboratory（苏州国家实验室）；University of Chinese Academy of Sciences（中国科学院大学）；Deutsches Elektronen-Synchrotron DESY（德国电子同步加速器）；Helmholtz-Zentrum hereon GmbH（亥姆霍兹海雷恩中心有限公司）；Technical University of Munich（慕尼黑工业大学）；Delft University of Technology（代尔夫特理工大学）；Max Planck Institute for Sustainable Materials（马克斯·普朗克可持续材料研究所）
Removing suspended solids and colloids are one of the most important water treatment processes. In this research, experimental tests have been done to assess the effects of pH and different doses of PACL on turbidity removal efficiency. The optimum dose of poly aluminum chloride (PACL) for removing turbidity was also determined. Turbidity was created artificially by adding the Kaolin with six different initial turbidities between 20 to 300 NTU rested for half an hour. The results have been showed that the best removal efficiency was at the pH of natural water. The optimal doses consumption of …
The surface or contact potential at the water liquid-vapor interface is discussed in relation to determinations of absolute ion hydration free energies and distributions of ions near the interface. It is shown that, rather than the surface potential itself, the net electrostatic potential at the center of an uncharged solute can aid both in relating differences between tabulations of hydration free energies and in explaining differing classical and quantum surface potential estimates. Quantum mechanical results are consistent with conclusions from classical simulations that there is a net driv…
Path-integral ab initio molecular dynamics (PI-AIMD) calculations have been employed to probe the nature of chloride ion solvation in aqueous solution. Nuclear quantum effects (NQEs) are shown to weaken hydrogen bonding between the chloride anion and the solvation shell of water molecules. As a consequence, the disruptive effect of the anion on the solvent water structure is significantly reduced compared to what is found in the absence of NQEs. The chloride hydration structure obtained from PI-AIMD agrees well with information extracted from neutron scattering data. Inparticular, the observed…
Vacuum Moisture Swing Direct Air Capture: A Low-Thermal, Water-Managed Pathway for Scalable CO2 Removal
The Steve Sanghi College of Engineering, Mechanical Engineering, Northern Arizona University（北亚利桑那大学史蒂夫·桑基工程学院）；Scientific Chemical Process Engineering Consultancy (SChPrEngCo)（科学化工过程工程咨询公司）
JILA, University of Colorado, Boulder（科罗拉多大学博尔德分校 JILA）；Department of Chemistry, University of Colorado, Boulder（科罗拉多大学博尔德分校化学系）；Sandia National Laboratories, Livermore（桑迪亚国家实验室）
Water pollution with pharmaceutical and personal care products has become a serious environmental. A reasonable strategy to mitigate the problem involves absorbent materials. In particular, the use of natural clays is an advantageous alternative considering their high adsorption capacity and compatibility with the environment. In the present work, the efficacy of a Cuban natural clay (palygorskite, Pal) as support of sulfamethoxazole (SMX), an antibiotic considered an emerging contaminant (EC), was evaluated. The amount of SMX incorporated onto clay was determined by UV spectroscopy. The resul…
