Physchem

Open AccessArticle

Thermodynamic Analysis of Ar_xXe₁_-_x Solid Solutions Based on Kirkwood–Buff Theory

by

Masafumi Miyaji

,

Jean-Marc Simon

and

Peter Krüger

Physchem 2022, 2(2), 191-206; https://doi.org/10.3390/physchem2020014 - 08 Jun 2022

Abstract

Kirkwood–Buff Integral (KBI) theory is an important method for the analysis of the structural and thermodynamic properties of liquid solutions. For solids, the calculation of KBIs has become possible only recently through the finite-volume generalisation of KBI theory, but it has so far [...] Read more.

Kirkwood–Buff Integral (KBI) theory is an important method for the analysis of the structural and thermodynamic properties of liquid solutions. For solids, the calculation of KBIs has become possible only recently through the finite-volume generalisation of KBI theory, but it has so far only been applied to monoatomic crystals. Here, we show that KBI theory can be applied to solid mixtures and compute the KBIs of a Ar

_{x}

Xe

_{1 - x}

solid solution, for

0 < x < 0.1

and temperature

T = 84 - 86

K, from pair distribution functions obtained by Monte Carlo simulation. From the KBIs, the isothermal compressibility, partial molar volumes, and thermodynamic factors are calculated and found to be in good agreement with alternative theoretical methods. The analysis of the KBIs and the partial molar volumes give insight into the structure of the mixture. The KBI of Ar pairs is much larger than that of Xe pairs, which indicates the tendency of Ar impurities to accumulate. The evolution of the partial molar volumes with increasing Ar molar fraction x shows a transition at

x \approx 0.06

, which reflects the formation of Ar clusters, precursors of the Ar-rich liquid phase. The calculated thermodynamic factors show that the solid(Xe) phase becomes unstable at

x \approx 0.1

, indicating the start of the solid (Xe)–liquid (Ar) equilibrium. The chemical potentials of Ar and Xe are obtained from the thermodynamic factor by integration over

ln x

, and by fitting the data to the Margules equations, the activity coefficients can be estimated over the whole composition range. The present findings extend the domain of applicability of the KBI solution theory from liquids to solids. Full article

(This article belongs to the Section Kinetics and Thermodynamics)

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Open AccessArticle

Formation of Metallic Ag on AgBr by Femtosecond Laser Irradiation

by

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,

and

Physchem 2022, 2(2), 179-190; https://doi.org/10.3390/physchem2020013 - 01 Jun 2022

Abstract

Laser irradiation of materials induces changes in their structure and functional properties. In this work, lattice heating and electronic excitation on silver bromide (AgBr), provoked by femtosecond laser irradiation, have been investigated by finite-temperature density functional theory and ab initio molecular dynamics calculations [...] Read more.

Laser irradiation of materials induces changes in their structure and functional properties. In this work, lattice heating and electronic excitation on silver bromide (AgBr), provoked by femtosecond laser irradiation, have been investigated by finite-temperature density functional theory and ab initio molecular dynamics calculations by using the two-temperature model. According to our results, the electronic temperature of 0.25 eV is enough to excite the electrons from the valence to the conduction band, whereas 1.00 eV changes the structural properties of the irradiated AgBr material. Charge density simulations also show that an Ag clustering process and the formation of Br₃⁻ complexes take place when the electronic temperature reaches 2.00 eV and 5.00 eV, respectively. The present results can be used to obtain coherent control of the extreme nonequilibrium conditions due to femtosecond laser irradiation for designing new functional materials. Full article

(This article belongs to the Section Theoretical and Computational Chemistry)

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Open AccessArticle

Anomalous Diffusion and Surface Effects on the Electric Response of Electrolytic Cells

by

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,

and

Physchem 2022, 2(2), 163-178; https://doi.org/10.3390/physchem2020012 - 17 May 2022

Abstract

We propose an anomalous diffusion approach to analyze the electrical impedance response of electrolytic cells using time-fractional derivatives. We establish, in general terms, the conservation laws connected to a modified displacement current entering the fractional approach formulation of the Poisson–Nernst–Planck (PNP) model. In [...] Read more.

We propose an anomalous diffusion approach to analyze the electrical impedance response of electrolytic cells using time-fractional derivatives. We establish, in general terms, the conservation laws connected to a modified displacement current entering the fractional approach formulation of the Poisson–Nernst–Planck (PNP) model. In this new formalism, we obtain analytical expressions for the electrical impedance for the case of blocking electrodes and in the presence of general integrodifferential boundary conditions including time-fractional derivatives of distributed order. A conceptual scenario thus emerges aimed at exploring anomalous diffusion and surface effects on the impedance response of the cell to an external stimulus. Full article

(This article belongs to the Section Mathematical Physics and Chemistry)

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Open AccessReview

Reactions of Graphene Nano-Flakes in Materials Chemistry and Astrophysics

by

Hiroto Tachikawa

and

Tetsuji Iyama

Physchem 2022, 2(2), 145-162; https://doi.org/10.3390/physchem2020011 - 12 May 2022

Abstract

The elucidation of the mechanism of the chemical evolution of the universe is one of the most important themes in astrophysics. Polycyclic aromatic hydrocarbons (PAHs) provide a two-dimensional reaction field in a three-dimensional interstellar space. Additionally, PAHs play an important role as a [...] Read more.

The elucidation of the mechanism of the chemical evolution of the universe is one of the most important themes in astrophysics. Polycyclic aromatic hydrocarbons (PAHs) provide a two-dimensional reaction field in a three-dimensional interstellar space. Additionally, PAHs play an important role as a model of graphene nanoflake (GNF) in materials chemistry. In the present review, we introduce our recent theoretical studies on the reactions of PAH and GNF with several molecules (or radicals). Furthermore, a hydrogen storage mechanism for alkali-doped GNFs and the molecular design of a reversible hydrogen storage device based on GNF will be introduced. Elucidating these reactions is important in understanding the chemical evolution of the universe and gives deeper insight into materials chemistry. Full article

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Open AccessArticle

Intrinsic Fluorometric Reporters of Pteridine Reductase 1, a Target for Antiparasitic Agents

by

Stefania Ferrari

,

Maria Paola Costi

and

Glauco Ponterini

Physchem 2022, 2(2), 131-144; https://doi.org/10.3390/physchem2020010 - 06 May 2022

Abstract

The intrinsic steady-state and time-resolved fluorescence of Leishmania major pteridine reductase 1, a tetrameric protein target for anti-infective agents, is investigated and deciphered in terms of the contributions from populations of the two tryptophans included in each protein monomer. Signals from these local [...] Read more.

The intrinsic steady-state and time-resolved fluorescence of Leishmania major pteridine reductase 1, a tetrameric protein target for anti-infective agents, is investigated and deciphered in terms of the contributions from populations of the two tryptophans included in each protein monomer. Signals from these local fluorometric reporters contain molecular-level information on the conformational landscape of this protein and on its interaction with a nanomolar pteridinic inhibitor. Full article

(This article belongs to the Section Biophysical Chemistry)

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Open AccessReview

Probing Nuclear Dipole Moments and Magnetic Shielding Constants through 3-Helium NMR Spectroscopy

by

Włodzimierz Makulski

Physchem 2022, 2(2), 116-130; https://doi.org/10.3390/physchem2020009 - 28 Apr 2022

Abstract

Multinuclear NMR studies of the gaseous mixtures that involve volatile compounds and ³He atoms are featured in this review. The precise analyses of ³He and other nuclei resonance frequencies show linear dependencies on gas density. Extrapolation of the gas phase results [...] Read more.

Multinuclear NMR studies of the gaseous mixtures that involve volatile compounds and ³He atoms are featured in this review. The precise analyses of ³He and other nuclei resonance frequencies show linear dependencies on gas density. Extrapolation of the gas phase results to the zero-pressure limit gives the ν₀(³He) and ν₀(ⁿX) resonance frequencies of nuclei in a single 3-helium atom and nuclei in molecules at a given temperature. The NMR frequency comparison method provides an approach for determining different nuclear magnetic moments. The application of quantum chemical shielding calculations, which include a more complete and careful theoretical treatment, allows the shielding of isolated molecules to be achieved with great accuracy and precision. They are used for the evaluation of nuclear moments, without shielding impacts on the bare nuclei, for: ^10/11B, ¹³C, ¹⁴N, ¹⁷O, ¹⁹F, ²¹Ne, ²⁹Si, ³¹P, ³³S, ^35/37Cl, ³³S, ⁸³Kr, ^129/131Xe, and ¹⁸³W. On the other hand, new results of nuclear moments were used for the reevaluation of absolute nuclear magnetic shielding in the molecules under study. Additionally, ³He gas in water solutions of lithium and sodium salts was used for measuring ^6/7Li and ²³Na magnetic moments and reevaluating the shielding parameters of Li⁺ and Na⁺ water-solvated cations. In this paper, guest ³He atoms that play a role in probing the electron density in many host macromolecules are also presented. Full article

(This article belongs to the Section Experimental and Computational Spectroscopy)

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Open AccessArticle

Assignment of the Vibrational Spectra of Diiron Nonacarbonyl, Fe₂(CO)₉

by

Stewart F. Parker

Physchem 2022, 2(2), 108-115; https://doi.org/10.3390/physchem2020008 - 05 Apr 2022

Abstract

Diiron nonacarbonyl, Fe₂(CO)₉, was discovered in 1905 and was the third metal carbonyl to be found. It was the first to be synthesized by a photochemical route. This is a challenging material to study: it is insoluble in virtually [...] Read more.

Diiron nonacarbonyl, Fe₂(CO)₉, was discovered in 1905 and was the third metal carbonyl to be found. It was the first to be synthesized by a photochemical route. This is a challenging material to study: it is insoluble in virtually all solvents and decomposes at 373 K before melting. This means that only solid-state spectroscopic data are available. New infrared, Raman and inelastic neutron scattering (INS) spectra have been measured and used to generate a complete assignment of the vibrational spectra of Fe₂(CO)₉. Density functional theory (DFT) calculations are used to support the assignments; however, for this material, they are much less useful than expected, although the calculated intensities provide crucial information. Full article

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Open AccessArticle

Many Body Current Density from Foldy–Wouthuysen Transformation of the Dirac–Coulomb Hamiltonian

by

Francesco Ferdinando Summa

and

Roberta Citro

Physchem 2022, 2(2), 96-107; https://doi.org/10.3390/physchem2020007 - 02 Apr 2022

Abstract

This paper analyzes how special relativity changes the equation for the many-body-induced current density starting from the Foldy–Wouthuysen diagonalization of the Dirac–Coulomb Hamiltonian. This current density differs from that obtained with the Gordon decomposition due to the presence of a spin-orbit coupling contribution [...] Read more.

This paper analyzes how special relativity changes the equation for the many-body-induced current density starting from the Foldy–Wouthuysen diagonalization of the Dirac–Coulomb Hamiltonian. This current density differs from that obtained with the Gordon decomposition due to the presence of a spin-orbit coupling contribution not considered before for many-body molecular systems. This contribution diverges on atomic nuclei due to the nature of the point charges considered in the nonrelativistic approach, demonstrating that conventionally used nonrelativistic methods are not suitable for dealing with spin effects such as spin-orbit coupling or effects smaller than

α^{2}

, with

α

the fine structure constant, and that a fully relativistic approach with a finite charge should be used. Despite the singularity, the spin-orbit coupling current becomes an important contribution to the total current in open-shell systems with high-spin multiplicity and a high atomic number in the nuclear proximity. On long ranges, this contribution is overcome by the Coulomb potential and the derived electric field which decays very quickly for small distances from nuclear charges. An evaluation of this spin-orbit current has been performed in the linear response approach at the HF/DFT level of theory. Full article

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Open AccessReview

Advanced Machine Learning Methods for Learning from Sparse Data in High-Dimensional Spaces: A Perspective on Uses in the Upstream of Development of Novel Energy Technologies

by

Sergei Manzhos

and

Manabu Ihara

Physchem 2022, 2(2), 72-95; https://doi.org/10.3390/physchem2020006 - 29 Mar 2022

Abstract

Machine learning (ML) has found increasing use in physical sciences, including research on energy conversion and storage technologies, in particular, so-called sustainable technologies. While often ML is used to directly optimize the parameters or phenomena of interest in the space of features, in [...] Read more.

Machine learning (ML) has found increasing use in physical sciences, including research on energy conversion and storage technologies, in particular, so-called sustainable technologies. While often ML is used to directly optimize the parameters or phenomena of interest in the space of features, in this perspective, we focus on using ML to construct objects and methods that help in or enable the modeling of the underlying phenomena. We highlight the need for machine learning from very sparse and unevenly distributed numeric data in multidimensional spaces in these applications. After a brief introduction of some common regression-type machine learning techniques, we focus on more advanced ML techniques which use these known methods as building blocks of more complex schemes and thereby allow working with extremely sparse data and also allow generating insight. Specifically, we will highlight the utility of using representations with subdimensional functions by combining the high-dimensional model representation ansatz with machine learning methods such as neural networks or Gaussian process regressions in applications ranging from heterogeneous catalysis to nuclear energy. Full article

(This article belongs to the Special Issue Data-Driven Research in Physical Chemistry)

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Open AccessArticle

A Comparison between the Lower Critical Solution Temperature Behavior of Polymers and Biomacromolecules

by

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and

Yaroslava G. Yingling

Physchem 2022, 2(1), 52-71; https://doi.org/10.3390/physchem2010005 - 18 Mar 2022

Abstract

All-atom molecular dynamics (MD) simulations are employed to compare the lower critical solution temperature (LCST) behaviors of poly(N-isopropylacrylamide) (PNIPAM) and elastin-like polypeptides (ELPs) with the canonical Val-Pro-Gly-Val-Gly ((VPGVG)_n) sequence over a range of temperatures from 280 K to 380 K. Our [...] Read more.

All-atom molecular dynamics (MD) simulations are employed to compare the lower critical solution temperature (LCST) behaviors of poly(N-isopropylacrylamide) (PNIPAM) and elastin-like polypeptides (ELPs) with the canonical Val-Pro-Gly-Val-Gly ((VPGVG)_n) sequence over a range of temperatures from 280 K to 380 K. Our simulations suggest that the structure of proximal water dictates the conformation of both the (VPGVG)_n ELPs and PNIPAM chains. Specifically, the LCST transition in ELPs can be attributed to a combination of thermal disruption of the network of the proximal water near both hydrophilic and hydrophobic groups in the backbone and side-chain of (VPGVG)_n, resulting in a reduction in solvent accessible surface area (SASA). This is accompanied with an increase in the secondary structure above its LCST. In the case of PNIPAM, the LCST transition is a result of a combination of a reduction in the hydrophobic SASA primarily due to the contributions of isopropyl side-chain and less to the backbone and the formation of intra-chain hydrogen bonds between the amide groups on the side-chain above its LCST. Full article

(This article belongs to the Section Theoretical and Computational Chemistry)

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Open AccessArticle

Computational Study of Crystallography, Defects, Ion Migration and Dopants in Almandine Garnet

by

Janya Lumbini Subasinghe

,

Sashikesh Ganeshalingam

and

Navaratnarajah Kuganathan

Physchem 2022, 2(1), 43-51; https://doi.org/10.3390/physchem2010004 - 17 Mar 2022

Abstract

Almandine garnet has received considerable amounts of interest due to its application in manufacturing and engineering processes. Defect processes, Fe-ion diffusion pathways, and promising dopants on the Al, Fe, and Si sites are examined using classical pair potential simulations in almandine garnet. The [...] Read more.

Almandine garnet has received considerable amounts of interest due to its application in manufacturing and engineering processes. Defect processes, Fe-ion diffusion pathways, and promising dopants on the Al, Fe, and Si sites are examined using classical pair potential simulations in almandine garnet. The cation antisite (Al–Si) defect cluster is the most favourable defect, highlighting the cation disorder in this material. A three-dimensional long-range Fe-ion diffusion pathway with an activation energy of 0.44 eV suggests that the ionic conductivity in this material is high. The most favourable isovalent dopants on the Fe, Al, and Si sites were found to be the Mn, Ga, and Ge, respectively. Subvalent doping of Ga on the Si site is a favourable process to increase the Fe content in this material. Full article

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Open AccessReview

Phase Change Materials with Enhanced Thermal Conductivity and Heat Propagation in Them

by

Alexander V. Eletskii

Physchem 2022, 2(1), 18-42; https://doi.org/10.3390/physchem2010003 - 28 Feb 2022

Abstract

The review contains information o; n the properties of phase-change materials (PCM) and the possibilities of their use as the basis of thermal energy storage. Special attention is given to PCMs with a phase transition temperature ranging between 20 and 80 °C since [...] Read more.

The review contains information o; n the properties of phase-change materials (PCM) and the possibilities of their use as the basis of thermal energy storage. Special attention is given to PCMs with a phase transition temperature ranging between 20 and 80 °C since such materials can be effectively used to reduce temperature variations in residential and industrial rooms. Thus, the application of PCMs in the construction industry enables one to considerably reduce the power consumption and reduce the negative environmental impact of industrial facilities. Thermophysical characteristics of the main types of PCMs are presented. The heat balance for a room with walls made of PCM-added materials is estimated. The calculations demonstrate that such structures can stabilize the temperature in practical applications as a result of the usage of such materials. The construction of a thermal accumulator on the basis of PCM is proposed and analyzed. This facility uses water as a working fluid and paraffin as a PCM. The thermal accumulator has a modular structure so that the number of similar modules is determined by the quantity of energy to be stored. The potential of wide application of PCMs as a basis for thermal energy storage is rather limited due to a very low conductivity (less than 1 W/(m K)) inherent to these materials. This drawback can be overcome by adding carbon nanoparticles whose thermal conductivity is four to five orders of magnitude greater than that of the matrix material. The problem of fabrication of polymer composites with enhanced thermal conductivity due to nanocarbon particles doping is discussed in detail. Full article

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Open AccessEditorial

Welcome to Physchem: Status and Prospects

by

Jacinto Sá

,

Sergei Manzhos

and

Vincenzo Barone

Physchem 2022, 2(1), 16-17; https://doi.org/10.3390/physchem2010002 - 27 Feb 2022

Abstract

We begin with passing on our very best wishes to the community for a healthy and prosperous 2022 [...] Full article

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Open AccessReview

An Overview of Common Infrared Techniques for Detecting CO Intermediates on Metal Surfaces for Hydrocarbon Products

by

Ahmed M. El-Zohry

Physchem 2022, 2(1), 1-15; https://doi.org/10.3390/physchem2010001 - 08 Jan 2022

Abstract

Detection of intermediates during the catalytic process by infrared techniques has been widely implemented for many important reactions. For the reduction of CO₂ into hydrocarbons on metal surfaces, CO molecule is one of the most important transient species to be followed due [...] Read more.

Detection of intermediates during the catalytic process by infrared techniques has been widely implemented for many important reactions. For the reduction of CO₂ into hydrocarbons on metal surfaces, CO molecule is one of the most important transient species to be followed due to its involvement in several products’ pathways, and its distinct vibrational features. Herein, basic understandings behind these utilized infrared techniques are illustrated aiming for highlighting the potential of each infrared technique and its advantages over the other ones for detecting CO molecules on metal surfaces. Full article

(This article belongs to the Special Issue Physical Chemistry Perspectives for the New Decade)

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Open AccessArticle

Acid-Catalyzed Esterification of Betaines: Theoretical Exploration of the Impact of the Carbon Chain Length on the Reaction Mechanism

by

Richail Dubien Moulandou-Koumba

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,

and

Physchem 2021, 1(3), 288-296; https://doi.org/10.3390/physchem1030022 - 07 Dec 2021

Abstract

Betaine derivatives, especially esters, are compounds of interest for the development of a more sustainable fine chemistry, as they are widely available from biomass and currently produced as side-products from various industries (among which, sugar production). In this publication, we studied the impact [...] Read more.

Betaine derivatives, especially esters, are compounds of interest for the development of a more sustainable fine chemistry, as they are widely available from biomass and currently produced as side-products from various industries (among which, sugar production). In this publication, we studied the impact of carbon chain length on three considered reaction mechanisms for the esterification of (CH₃)₃N(CH₂)_nCO₂ betaine (n = 1, 2, 3) with glycerol under acid catalysis. DFT calculations show that the mechanism proposed by Bachmann–Frapper et al. may also be active here, but it can interestingly be seen as an avatar of the former proposition by Watson. Conversely, Ingold’s proposition is in this case too energetically prevented. Overall, lower activation barriers and higher reaction exergonicity are reported, suggesting esterification of longer carbon-chain based betaines is more readily achieved. Full article

(This article belongs to the Special Issue Physical Chemistry Perspectives for the New Decade)

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Open AccessReview

Surface Coatings and Treatments for Controlled Hydrate Formation: A Mini Review

by

Tausif Altamash

,

José M. S. S. Esperança

and

Mohammad Tariq

Physchem 2021, 1(3), 272-287; https://doi.org/10.3390/physchem1030021 - 04 Dec 2021

Cited by 2

Abstract

Gas hydrates (GHs) are known to pose serious flow assurance challenges for the oil and gas industry. Neverthless, over the last few decades, gas hydrates-based technology has been explored for various energy- and environmentally related applications. For both applications, a controlled formation of [...] Read more.

Gas hydrates (GHs) are known to pose serious flow assurance challenges for the oil and gas industry. Neverthless, over the last few decades, gas hydrates-based technology has been explored for various energy- and environmentally related applications. For both applications, a controlled formation of GHs is desired. Management of hydrate formation by allowing them to form within the pipelines in a controlled form over their complete mitigation is preferred. Moreover, environmental, benign, non-chemical methods to accelerate the rate of hydrate formation are in demand. This review focused on the progress made in the last decade on the use of various surface coatings and treatments to control the hydrate formation at atmospheric pressure and in realistic conditions of high pressure. It can be inferred that both surface chemistry (hydrophobicity/hydrophilicity) and surface morphology play a significant role in deciding the hydrate adhesion on a given surface. Full article

(This article belongs to the Section Kinetics and Thermodynamics)

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Open AccessArticle

Identification of Adsorbed Species and Surface Chemical State on Ag(111) in the Presence of Ethylene and Oxygen Studied with Infrared and X-ray Spectroscopies

by

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and

Physchem 2021, 1(3), 259-271; https://doi.org/10.3390/physchem1030020 - 12 Nov 2021

Abstract

Using a combination of two surface-sensitive spectroscopy techniques, the chemical state of the Ag(111) surface and the nature of the adsorbed species in the presence of ethylene and oxygen gases are identified. In the 10 mbar pressure range and 25–200 °C studied here, [...] Read more.

Using a combination of two surface-sensitive spectroscopy techniques, the chemical state of the Ag(111) surface and the nature of the adsorbed species in the presence of ethylene and oxygen gases are identified. In the 10 mbar pressure range and 25–200 °C studied here, Ag(111) remains largely metallic even in O₂-rich conditions. The only adsorbed molecular species with a low but discernible coverage is surface carbonate, which forms due to further oxidation of produced CO₂, in a similar manner to its formation in ambient air on Ag surfaces. Its formation is also pressure-dependent, for instance, it is not observed when the total pressure is in the 1 mbar pressure range. Production of carbonate, along with carbon dioxide and water vapor as the main gas-phase products, suggests that an unpromoted Ag(111) surface catalyzes mainly the undesired full oxidation reaction. Full article

(This article belongs to the Special Issue Novel Characterization Tools for Catalysis of Energy-Transition Related Reactions)

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Open AccessArticle

The Local Structure of the BiS₂ Layer in RE(O,F)BiS₂ Determined by In-Plane Polarized X-ray Absorption Measurements

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and

Physchem 2021, 1(3), 250-258; https://doi.org/10.3390/physchem1030019 - 10 Nov 2021

Abstract

We have investigated the local structure of BiS

_{2}

-based layered materials by Bi L

_{3}

-edge extended X-ray absorption fine structure (EXAFS) measurements performed on single crystal samples with polarization of the X-ray beam parallel to the BiS

_{2}

plane. The results [...] Read more.

We have investigated the local structure of BiS

_{2}

-based layered materials by Bi L

_{3}

-edge extended X-ray absorption fine structure (EXAFS) measurements performed on single crystal samples with polarization of the X-ray beam parallel to the BiS

_{2}

plane. The results confirm highly instable nature of BiS

_{2}

layer, characterized by ferroelectric like distortions. The distortion amplitude, determined by the separation between the two in-plane (Bi-S1) bonds, is found to be highest in LaO

_{0.77}

F

_{0.23}

BiS

_{2}

with

Δ

R∼0.26 Å and lowest in NdO

_{0.71}

F

_{0.29}

BiS

_{2}

with

Δ

R∼0.13 Å. Among the systems with intrinsic doping, CeOBiS

_{2}

shows smaller distortion (

Δ

R∼0.15 Å) than PrOBiS

_{2}

(

Δ

R∼0.18 Å) while the highest distortion appears for EuFBiS

_{2}

revealing

Δ

R∼0.22 Å. It appears that the distortion amplitude is controlled by the nature of the RE(O,F) spacer layer in the RE(O,F)BiS

_{2}

structure. The X-ray absorption near edge structure (XANES) spectra, probing the local geometry, shows a spectral weight transfer that evolves systematically with the distortion amplitude in the BiS

_{2}

-layer. The results provide a quantitative measurements of the local distortions in the instable BiS

_{2}

-layer with direct implication on the physical properties of these materials. Full article

(This article belongs to the Special Issue Physical Chemistry Perspectives for the New Decade)

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Open AccessPerspective

Toward Computational Accuracy in Realistic Systems to Aid Understanding of Field-Level Water Quality Issues

by

William A. Alexander

Physchem 2021, 1(3), 243-249; https://doi.org/10.3390/physchem1030018 - 31 Oct 2021

Abstract

Contemplating what will unfold in this new decade and those after, it is not difficult to imagine the increasing importance of conservation and protection of clean water supplies. A worrying but predictable offshoot of humanity’s technological advances is the seemingly ever-increasing chemical load [...] Read more.

Contemplating what will unfold in this new decade and those after, it is not difficult to imagine the increasing importance of conservation and protection of clean water supplies. A worrying but predictable offshoot of humanity’s technological advances is the seemingly ever-increasing chemical load burdening our waterways. In this perspective are presented a few modest areas where computational chemistry modelling could provide benefit to these efforts by harnessing the continually improving computational power available to the field. In the acute event of a chemical spill incident, true quantum-chemistry-based predictions of physicochemical properties and surface-binding behaviors can be used to help decision making in remediating the spill threat. The chronic burdens of microplastics and perfluorinated “forever chemicals” can also be addressed with computational modelling to fill the gap between feasible laboratory experiment timescales and the much-longer material lifetimes. For all of these systems, field-level accuracy models will avail themselves as the model computational systems are able to incorporate more realistic features that are relevant to water quality issues. Full article

(This article belongs to the Special Issue Physical Chemistry Perspectives for the New Decade)

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