Self-limited Growth of an Oxyhydroxide Phase at the Fe3O4(001) Surface in Liquid and Ambient Pressure Water
Florian Kraushofer, Francesca Mirabella, Jian Xu, Jiří Pavelec, Jan Balajka, Matthias Müllner, Nikolaus Resch, Zdeněk Jakub, Jan Hulva, Matthias Meier, Michael … 展开作者
Florian Kraushofer, Francesca Mirabella, Jian Xu, Jiří Pavelec, Jan Balajka, Matthias Müllner, Nikolaus Resch, Zdeněk Jakub, Jan Hulva, Matthias Meier, Michael Schmid, Ulrike Diebold, Gareth S. Parkinson
Atomic-scale investigations of metal oxide surfaces exposed to aqueous environments are vital to understand degradation phenomena (e.g. dissolution and corrosion) as well as the performance of these materials in applications. Here, we utilize a new experimental setup for the UHV-compatible dosing of liquids to explore the stability of the Fe3O4(001)-c(2x2) surface following exposure to liquid and ambient pressure water. X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) data show that extensive hydroxylation causes the surface to revert to a bulk-like (1x1) termination. However, scanning tunnelling microscopy (STM) images reveal a more complex situation, with the slow growth of an oxyhydroxide phase, which ultimately saturates at approximately 40% coverage. We conclude that the new material contains OH groups from dissociated water coordinated to Fe cations extracted from subsurface layers, and that the surface passivates once the surface oxygen lattice is saturated with H because no further dissociation can take place. The resemblance of the STM images to those acquired in previous electrochemical STM (EC-STM) studies lead us to believe a similar structure exists at the solid-electrolyte interface during immersion at pH 7.
Path-integral molecular dynamics simulations based on density functional theory employing exchange-correlation density functionals capable of treating nonlocal van der Waals (vdW) interactions self-consistently provide a remarkably accurate description of ambient water. Moreover, they suggest that water's structure may be impacted by a combined influence between nuclear quantum effects and vdW interactions. The latter strongly favor the formation of a high-density liquid, whereas the inclusion of the former mitigates this by decreasing the mean hydrogen-bond (H-bond) distance. Examining the st…
Raman spectroscopy examination of the 25 deg-C water freezing under compression revealed transition from 1.35 GPa to 0.86 GPa upon ice being formed at continued volume change. The transition is associated with a slight blue shift of the high-frequency phonon (omiga_H ~ 3120 cm-1) and creation of the low-frequency phonons (Omiga_L ~ 200 cm-1). In the liquid and in the solid phase, the increased pressure softens the Omiga_H and stiffens the Omida_L, which indicates the presence of the inter-electron-pair repulsion in both liquid and solid water.
In temperature range from 0 C to 100 C, abnormality of ambient water properties, at normal pressure, are mainly defined by the physic of hydrogen bonds in supramolecular structures (SMS). Application of Arrhenius approximations and modification of temperature dependences (TDs) for 15 physical characteristics of water made it possible to define their activation energies and to differentiate the contributions of equilibrium thermal processes and those of SMS reconfigurations. Reactions of hydrogen bonds breakage and those of hexagonal ice-like clusters transformation limit TDs of viscosity and r…
Oxygen Isotope Exchange Between Molten Silicate Spherules and Ambient Water Vapor with Nonzero Relative Velocity: Implication for Chondrule Formation Environment
The liquid and supercooled states of water show a series of anomalies whose nature is debated. A key role is attributed to the formation of structural aggregates induced by critical phenomena occurring deep in the supercooled region; the nature of the water anomalies and of the hidden critical processes remains elusive. Here we report a time-resolved optical Kerr effect investigation of the vibrational dynamics and relaxation processes in supercooled bulk water. The experiment measures the water intermolecular vibrations and the structural relaxation process in an extended temperature range, a…
We study ion pair dissociation in water at ambient conditions using a combination of classical and ab initio approaches. The goal of this study is to disentangle the sources of discrepancy observed in computed potentials of mean force. In particular we aim to understand why some models favor the stability of solvent-separated ion pairs versus contact ion pairs. We found that some observed differences can be explained by non-converged simulation parameters. However, we also unveil that for some models, small changes in the solution density can have significant effects on modifying the equilibri…
Within the framework of density functional theory, the inclusion of exact exchange and non-local van der Waals/dispersion (vdW) interactions is crucial for predicting a microscopic structure of ambient liquid water that quantitatively agrees with experiment. In this work, we have used the local structure index (LSI) order parameter to analyze the local structure in such highly accurate $ab$ $initio$ liquid water. At ambient conditions, the LSI probability distribution, P($I$), was unimodal with most water molecules characterized by more disordered high-density-like local environments. With the…
The structure of liquid water at ambient conditions is studied in ab initio molecular dynamics simulations using van der Waals (vdW) density-functional theory, i.e. using the new exchange-correlation functionals optPBE-vdW and vdW-DF2. Inclusion of the more isotropic vdW interactions counteracts highly directional hydrogen-bonds, which are enhanced by standard functionals. This brings about a softening of the microscopic structure of water, as seen from the broadening of angular distribution functions and, in particular, from the much lower and broader first peak in the oxygen-oxygen pair-corr…
Many experimental techniques such as tagging photodissociation and helium nanodroplet isolation spectroscopy operate at very low temperatures in order to investigate hydrogen bonding. To elucidate the differences between such ultra-cold and usual ambient conditions, different hydrogen bonded systems are studied systematically from 300 K down to about 1 K using path integral simulations that explicitly consider both, the quantum nature of the nuclei and thermal fluctuations. For that purpose, finite sized water clusters, specifically the water dimer and hexamer, protonated water clusters includ…
The heat capacities of ice and water at ambient pressure are reexamined to build an intrinsic correlation between H2O molecular motions and the heat capacity. Based on the evolution of H2O molecular motions, a satisfactory description of the heat capacity of ice and water is provided. The heat capacity of ice is related not only to H2O molecular vibrations, but also to the molecular rotations. In water, all H2O molecular vibrations, rotations and translations contribute to the heat capacity. The molecular translational motions are found to be the main contribution to the large heat capacity of…
Water under nanoconfinement at ambient conditions has exhibited low-dimensional ice formation and liquid-solid phase transitions, but with structural and dynamical signatures which map onto known regions of waters phase diagram. Using THz absorption spectroscopy and ab initio molecular dynamics, we have investigated the ambient water confined in a supramolecular tetrahedral assembly, and determined that a distinct network of 9-10 water molecules is present within the nanocavity of the host. The low-frequency absorption spectrum and theoretical analysis of the water in the $Ga_4$$L_6$$^{-12}$ h…
Density-functional theory (DFT) has been widely used to study water and ice for at least 20 years. However, the reliability of different DFT exchange-correlation (xc) functionals for water remains a matter of considerable debate. This is particularly true in light of the recent development of DFT based methods that account for van der Waals (vdW) dispersion forces. Here, we report a detailed study with several xc functionals (semi-local, hybrid, and vdW inclusive approaches) on ice Ih and six proton ordered phases of ice. Consistent with our previous study [Phys. Rev. Lett. 107, 185701 (2011)]…
The contributed paper by Naserifar and Goddard reports that their RexPoN water model under ambient conditions simulates liquid water as a dynamic polydisperse branched polymer, which they speculate explains the existence of the liquid-liquid critical point (LLCP) in the supercooled region. Our work addresses several serious factual errors and needless speculation in their paper about their interpretation of their model and its implication for the LLCP in supercooled water.
We determine and compare structural, dynamical, and electronic properties of liquid water at near ambient conditions through density-functional molecular dynamics simulations, when using either plane-wave or atomic-orbital basis sets. In both frameworks, the electronic structure and the atomic forces are self-consistently determined within the same theoretical scheme based on a nonlocal density functional accounting for van der Waals interactions. The overall properties of liquid water achieved within the two frameworks are in excellent agreement with each other. Thus, our study supports that …
Finite-range numerical atomic orbitals are the basis functions of choice for several first principles methods, due to their flexibility and scalability. Generating and testing such basis sets, however, remains a significant challenge for the end user. We discuss these issues and present a new scheme for generating improved polarization orbitals of finite range. We then develop a series of high-accuracy basis sets for the water molecule, and report on their performance in describing the monomer and dimer, two phases of ice, and liquid water at ambient and high density. The tests are performed b…
Using Lifshitz theory we assess the role of van der Waals forces at interfaces of ice and water. The results are combined with measured structural forces from computer simulations to develop a quantitative model of the surface free energy of premelting films. This input is employed within the framework of wetting theory and allows us to predict qualitatively the behavior of quasi-liquid layer thickness as a function of ambient conditions. Our results emphasizes the significance of vapor pressure. The ice vapor interface is shown to exhibit only incomplete premelting, but the situation can shif…
Liquid water at ambient temperature displays ultrafast molecular motions and concomitant fluctuations of very strong electric fields originating from the dipolar H2O molecules. We show that such random intermolecular fields induce tunnel ionization of water molecules, which becomes irreversible if an external terahertz (THz) pulse imposes an additional directed electric field on the liquid. Time-resolved nonlinear THz spectroscopy maps charge separation, transport and localization of the released electrons on a few-picosecond time scale. The highly polarizable localized electrons modify the TH…
In this work, we report the results of a series of density functional theory (DFT) based ab initio molecular dynamics (AIMD) simulations of ambient liquid water using a hierarchy of exchange-correlation (XC) functionals to investigate the individual and collective effects of exact exchange (Exx), via the PBE0 hybrid functional, non-local vdW/dispersion interactions, via a fully self-consistent density-dependent dispersion correction, and approximate nuclear quantum effects (aNQE), via a 30 K increase in the simulation temperature, on the microscopic structure of liquid water. Based on these AI…
Benchmarking semi-empirical quantum chemical methods on liquid water
Paderborn University（帕德博恩大学）；University of Bonn（波恩大学）；Center for Advanced Systems Understanding（先进系统理解中心）；Helmholtz Zentrum Dresden-Rossendorf（德累斯顿-罗斯多夫亥姆霍兹中心）；Microsoft Research（微软研究院）；University of Zurich（苏黎世大学）
A comprehensive microscopic understanding of ambient liquid water is a major challenge for $ab$ $initio$ simulations as it simultaneously requires an accurate quantum mechanical description of the underlying potential energy surface (PES) as well as extensive sampling of configuration space. Due to the presence of light atoms (e.g., H or D), nuclear quantum fluctuations lead to observable changes in the structural properties of liquid water (e.g., isotope effects), and therefore provide yet another challenge for $ab$ $initio$ approaches. In this work, we demonstrate that the combination of dis…
We have applied path integral simulations, in combination with new ab initio based water potentials, to investigate nuclear quantum effects in liquid water. Because direct ab initio path integral simulations are computationally expensive, a flexible water model is parameterized by force-matching to density functional theory-based molecular dynamics simulations. The resulting effective potentials provide an inexpensive replacement for direct ab inito molecular dynamics simulations and allow efficient simulation of nuclear quantum effects. Static and dynamic properties of liquid water at ambient…
The solvation structure of protons in aqueous media is highly relevant to electric properties and to proton transport in liquids and membranes. At ambient temperature, polar liquids display structural fluctuations on femto- to picosecond time scales with a direct impact on proton solvation. We apply two-dimensional infrared (2D-IR) spectroscopy for following proton dynamics in acetonitrile/water mixtures with the Zundel cation H$_5$O$_2^+$ prepared in neat acetonitrile as a benchmark. The 2D-IR spectra of the proton transfer mode of H$_5$O$_2^+$ demonstrate stochastic large-amplitude motions i…
We perform ab initio molecular dynamics (AIMD) simulation of liquid water in the canonical ensemble at ambient conditions using the SCAN meta-GGA functional approximation, and carry out systematic comparisons with the results obtained from the GGA-level PBE functional, and Tkatchenko-Scheffler van der Waals (vdW) dispersion correction inclusive PBE functional. We analyze various properties of liquid water including radial distribution functions, oxygen-oxygen-oxygen triplet angular distribution, tetrahedrality, hydrogen bonds, diffusion coefficients, ring statistics, density of states, band ga…
The evaporation coefficients of water in air and nitrogen were found as a function of temperature, by studying the evaporation of pure water droplet. The droplet was levitated in an electrodynamic trap placed in a climatic chamber maintaining atmospheric pressure. Droplet radius evolution and evaporation dynamics were studied with high precision by analyzing the angle-resolved light scattering Mie interference patterns. A model of quasi-stationary droplet evolution, accounting for the kinetic effects near the droplet surface was applied. In particular, the effect of thermal effusion (a short r…
First principles molecular dynamics simulation protocol is established using revised functional of Perdew-Burke-Ernzerhof (revPBE) in conjunction with Grimme's third generation of dispersion (D3) correction to describe properties of water at ambient conditions. This study also demonstrates the consistency of the structure of water across both isobaric (NpT) and isothermal (NVT) ensembles. Going beyond the standard structural benchmarks for liquid water, we compute properties that are connected to both local structure and mass density uctuations that are related to concepts of solvation and hyd…
Water is one of the most abundant substances on Earth, and ice, i.e., solid water, has more than 18 known phases. Normally ice in nature exists only as Ice Ih, Ice Ic, or a stacking disordered mixture of both. Although many theoretical efforts have been devoted to understanding the thermodynamics of different ice phases at ambient temperature and pressure, there still remains many puzzles. We simulated the reversible transitions between water and different ice phases by performing full atom molecular dynamics simulations. Using the enhanced sampling method MetaITS with the two selected X-ray d…
Adding salt to water at ambient pressure affects its thermodynamic properties. At low salt concentration, anomalies such as the density maximum are shifted to lower temperature, while at large enough salt concentration they cannot be observed any more. Here we investigate the effect of salt on an anomaly recently observed in pure water at negative pressure: the existence of a sound velocity minimum along isochores. We compare experiments and simulations for an aqueous solution of sodium chloride with molality around $1.2\,\mathrm{mol\,kg^{-1}}$, reaching pressures beyond $-100\,\mathrm{MPa}$. …
We investigate the structural properties of liquid water at near ambient conditions using first-principles molecular dynamics simulations based on a semilocal density functional augmented with nonlocal van der Waals interactions. The adopted scheme offers the advantage of simulating liquid water at essentially the same computational cost of standard semilocal functionals. Applied to the water dimer and to ice Ih, we find that the hydrogen-bond energy is only slightly enhanced compared to a standard semilocal functional. We simulate liquid water through molecular dynamics in the NpH statistical…
Water has many anomalous properties compared to "simple" liquids, and these anomalies are typically enhanced in supercooled water. While numerous models have been proposed, including the liquid-liquid critical point, the singularity-free scenario, and the stability limit conjecture, a molecular-level understanding remains elusive.The main difficulty in determining which, if any, of these models is correct is the limited amount of data in the relevant temperature and pressure ranges. For water at ambient pressures, which is the focus of this work, data is largely missing from 160 - 232 K due to…
The atomic scale insights into the interaction of water with oxide surface are essential for elucidating the mechanism of physiochemical processes in various scientific and practical fields, since the water is ubiquitous and coats multifarious material surface under ambient conditions. By utilizing periodic density functional theory calculations with van der Waals corrections, herein we report for the first time the energetically and thermodynamically favorable homolytic dissociative adsorption behavior of water over magnesia (001) films deposited on metal substrate. The water adsorption on pr…
Understanding the Raman spectroscopy at the atomistic level is important for the elucidation of dynamical processes in liquid water. Because the polarizability (or its time derivative) is often a highly nonlinear function of coordinates or/and momenta, we employ the linearized semiclassical initial value representation for quantum dynamical simulations of liquid water (and heavy water) under ambient conditions based on an ab initio based, flexible, polarizable model (the POLI2VS force field). It is shown that quantum dynamical effects play a critical role in reproducing the peaks in the interm…
