scholarly journals Charge Compensation by Iodine Covalent Bonding in Lead Iodide Perovskite Materials

Crystals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 88
Author(s):  
Anthony Ruth ◽  
Michael Holland ◽  
Angus Rockett ◽  
Erin Sanehira ◽  
Michael Irwin ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
High Performance ◽  
Density Functional ◽  
Defect Formation ◽  
Covalent Bonding ◽  
Binding Energies ◽  
Structural Motif ◽  
Lead Iodide ◽  
Excess Iodine ◽  
Perovskite Materials

Metal halide perovskite materials (MHPs) are a family of next-generation semiconductors that are enabling low-cost, high-performance solar cells and optoelectronic devices. The most-used halogen in MHPs, iodine, can supplement its octet by covalent bonding resulting in atomic charges intermediate to I− and I0. Here, we examine theoretically stabilized defects of iodine using density functional theory (DFT); defect formation enthalpies and iodine Bader charges which illustrate how MHPs adapt to stoichiometry changes. Experimentally, X-ray photoelectron spectroscopy (XPS) is used to identify perovskite defects and their relative binding energies, and validate the predicted chemical environments of iodine defects. Examining MHP samples with excess iodine compared with near stoichiometric samples, we discern additional spectral intensity in the I 3d5/2 XPS data arising from defects, and support the presence of iodine trimers. I 3d5/2 defect peak areas reveal a ratio of 2:1, matching the number of atoms at the ends and middle of the trimer, whereas their binding energies agree with calculated Bader charges. Results suggest the iodine trimer is the preferred structural motif for incorporation of excess iodine into the perovskite lattice. Understanding these easily formed photoactive defects and how to identify their presence is essential for stabilizing MHPs against photodecomposition.

scholarly journals Covalent Functionalization of Nickel Phosphide Nanocrystals with Aryl-Diazonium Salts

2021 ◽  
Author(s):  
Ian Murphy ◽  
Peter Rice ◽  
Madison Monahan ◽  
Leo Zasada ◽  
Elisa Miller ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Photoelectron Spectroscopy ◽  
Density Functional ◽  
Binding Energies ◽  
Diazonium Salts ◽  
Surface Functional Group ◽  
Covalent Functionalization ◽  
Substitution Pattern ◽  
Core Electron ◽  
Functional Theory

Covalent functionalization of Ni2P nanocrystals was demonstrated using aryl-diazonium salts. Spontaneous adsorption of aryl functional groups was observed, with surface coverages ranging from 20-96% depending on the native reactivity of the salt as determined by the aryl substitution pattern. Increased coverage was possible for low reactivity species using a sacrificial reductant. Functionalization was confirmed using thermogravimetric analysis, FTIR and X-ray photoelectron spectroscopy. The structure and energetics of this nanocrystal electrocatalyst system, as a function of ligand coverage, was explored with density functional theory calculations. The Hammett parameter of the surface functional group was found to linearly correlate with the change in Ni and P core-electron binding energies and the nanocrystal’s experimentally and computationally determined work-function. The electrocatalytic activity and stability of the functionalized nanocrystals for hydrogen evolution were also improved when compared to the unfunctionalized material, but a simple trend based on electrostatics was not evident. We used density functional theory to understand this discrepancy and found that H adsorption energies on the covalently functionalized Ni2P also do not follow the electrostatic trend and are predictive descriptors of the experimental results.

Theoretical core spectroscopy of molecules interacting with ice surfaces 

2021 ◽  
Author(s):  
Richard Asamoah Opoku
Keyword(s):  
Electronic Properties ◽  
Photoelectron Spectroscopy ◽  
Density Functional ◽  
Trace Gases ◽  
Binding Energies ◽  
Photoelectron Spectra ◽  
Development Fund ◽  
Xps Spectra ◽  
The Core ◽  
Ice Surfaces

<p><strong>Céline TOUBIN</strong><strong><sup>2</sup></strong><strong> and </strong><strong>André Severo Pereira GOMES</strong><strong><sup> 3</sup></strong></p><p><sup>2,3</sup> Laboratoire de Physique des Lasers, des atomes et des Molécules, Université de Lille, Cité Scientifique, 59655 Villeneuve d’Ascq Cedex, France</p><p>E-mail : [email protected]<sup>2</sup> ; [email protected]<sup>3</sup></p><p>Ice plays an essential role as a catalyst for reactions between atmospheric trace gases. The uptake of trace gases to ice has been proposed to have a major impact on geochemical cycles, human health, and ozone depletion in the stratosphere [1]. X-ray photoelectron spectroscopy (XPS) [2], serves as a powerful technique to characterize the elemental composition of such interacting species due to its surface sensitivity. Given the existence of complex physico-chemical processes such as adsorption, desorption, and migration within ice matrix, it is important to establish a theoretical framework to determine the electronic properties of these species under different conditions such as temperature and concentration. The focus of this work is to construct an embedding methodology employing Density Functional (DFT) and Wave Function Theory (WFT) to model and interpret photoelectron spectra of adsorbed halogenated species on ice surfaces at the core level with the highest accuracy possible. </p><p>We make use of an embedding approach utilizing full quantum mechanics to divide the system into subunits that will be treated at different levels of theory [3].</p><p>The goal is to determine core electron binding energies and the associated chemical shifts for the adsorbed halogenated species such as molecular HCl and the dissociated form Cl- at the surface and within the uppermost bulk layer of the ice respectively [4]. The core energy shifts are compared to the data derived from the XPS spectra [4].</p><p>We show that the use of a fully quantum mechanical embedding method, to treat solute-solvent systems is computationally efficient, yet accurate enough to determine the electronic properties of the solute system (halide ion) as well as the long-range effects of the solvent environment (ice).</p><p>We acknowledge support by the French government through the Program “Investissement d'avenir” through the Labex CaPPA (contract ANR-11-LABX-0005-01) and I-SITE ULNE project OVERSEE (contract ANR-16-IDEX-0004), CPER CLIMIBIO (European Regional Development Fund, Hauts de France council, French Ministry of Higher Education and Research) and French national supercomputing facilities (grants DARI x2016081859 and A0050801859).</p><p> </p>

Computational study of Mg insertion into amorphous silicon: advantageous energetics over crystalline silicon for Mg storage

2013 ◽  
Vol 1540 ◽  
Author(s):  
Fleur Legrain ◽  
Oleksandr I. Malyi ◽  
Teck L. Tan ◽  
Sergei Manzhos
Keyword(s):  
Density Functional ◽  
Nearest Neighbor ◽  
Defect Formation ◽  
Crystalline Silicon ◽  
Computational Study ◽  
Binding Energies ◽  
Functional Theory ◽  
Wide Range ◽  
Insertion Sites ◽  
Formation Energies

ABSTRACTWe show in a theoretical density functional theory study that amorphous Si (a-Si) has more favorable energetics for Mg storage compared to crystalline Si (c-Si). Specifically, Mg and Li insertion is compared in a model a-Si simulation cell. Multiple sites for Mg insertion with a wide range of binding energies are identified. For many sites, Mg defect formation energies are negative, whereas they are positive in c-Si. Moreover, while clustering in c-Si destabilizes the insertion sites (by about 0.1/0.2 eV per atom for nearest-neighbor Li/Mg), it is found to stabilize some of the insertion sites for both Li (by up to 0.27 eV) and Mg (by up to 0.35 eV) in a-Si. This could have significant implications on the performance of Si anodes in Mg batteries.

scholarly journals Resonant Ta Doping for Enhanced Mobility in Transparent Conducting SnO2

2019 ◽  
Author(s):  
Benjamin Williamson ◽  
Thomas Featherstone ◽  
Sanjayan Sathasivam ◽  
Jack Swallow ◽  
Huw Shiel ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
High Performance ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Consumer Electronics ◽  
Electron Effective Mass ◽  
Conducting Oxides ◽  
Transparent Conducting ◽  
Earth Abundant ◽  
Sb Doping

<div>Transparent conducting oxides (TCOs) are ubiquitous in modern consumer electronics. SnO<sub>2</sub> is an earth abundant, cheaper alternative to In<sub>2</sub>O<sub>3</sub> as a TCO however, its performance in terms of electrical properties lags behind that of In<sub>2</sub>O<sub>3</sub>. Based on the recent discovery of mobility and conductivity enhancements in In<sub>2</sub>O<sub>3</sub> from resonant dopants, we use a combination of state-of-the-art hybrid density functional theory calculations, high resolution photoelectron spectroscopy and semiconductor statistics modelling to understand what the optimal dopant is to maximise performance of SnO<sub>2</sub>-based TCOs. We demonstrate that Ta is the optimal dopant for high performance SnO<sub>2</sub>, as it is a resonant dopant which is readily incorporated into SnO<sub>2</sub> with the Ta 5d states sitting ~1.4 eV above the conduction band minimum. Experimentally, the electron effective mass of Ta doped SnO<sub>2</sub> was shown to be 0.23m<sub>0</sub>, compared to 0.29m<sub>0</sub> seen with conventional Sb doping, explaining its ability to yield higher mobilities and conductivities.</div><div><br></div>

scholarly journals Resonant Ta Doping for Enhanced Mobility in Transparent Conducting SnO2

2019 ◽  
Author(s):  
Benjamin Williamson ◽  
Thomas Featherstone ◽  
Sanjayan Sathasivam ◽  
Jack Swallow ◽  
Huw Shiel ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
High Performance ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Consumer Electronics ◽  
Electron Effective Mass ◽  
Conducting Oxides ◽  
Transparent Conducting ◽  
Earth Abundant ◽  
Sb Doping

<div>Transparent conducting oxides (TCOs) are ubiquitous in modern consumer electronics. SnO<sub>2</sub> is an earth abundant, cheaper alternative to In<sub>2</sub>O<sub>3</sub> as a TCO however, its performance in terms of electrical properties lags behind that of In<sub>2</sub>O<sub>3</sub>. Based on the recent discovery of mobility and conductivity enhancements in In<sub>2</sub>O<sub>3</sub> from resonant dopants, we use a combination of state-of-the-art hybrid density functional theory calculations, high resolution photoelectron spectroscopy and semiconductor statistics modelling to understand what the optimal dopant is to maximise performance of SnO<sub>2</sub>-based TCOs. We demonstrate that Ta is the optimal dopant for high performance SnO<sub>2</sub>, as it is a resonant dopant which is readily incorporated into SnO<sub>2</sub> with the Ta 5d states sitting ~1.4 eV above the conduction band minimum. Experimentally, the electron effective mass of Ta doped SnO<sub>2</sub> was shown to be 0.23m<sub>0</sub>, compared to 0.29m<sub>0</sub> seen with conventional Sb doping, explaining its ability to yield higher mobilities and conductivities.</div><div><br></div>

scholarly journals Covalent Functionalization of Nickel Phosphide Nanocrystals with Aryl-Diazonium Salts

2021 ◽  
Author(s):  
Ian Murphy ◽  
Peter Rice ◽  
Madison Monahan ◽  
Leo Zasada ◽  
Elisa Miller ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Photoelectron Spectroscopy ◽  
Density Functional ◽  
Binding Energies ◽  
Diazonium Salts ◽  
Surface Functional Group ◽  
Covalent Functionalization ◽  
Substitution Pattern ◽  
Core Electron ◽  
Functional Theory

Covalent functionalization of Ni2P nanocrystals was demonstrated using aryl-diazonium salts. Spontaneous adsorption of aryl functional groups was observed, with surface coverages ranging from 20-96% depending on the native reactivity of the salt as determined by the aryl substitution pattern. Increased coverage was possible for low reactivity species using a sacrificial reductant. Functionalization was confirmed using thermogravimetric analysis, FTIR and X-ray photoelectron spectroscopy. The structure and energetics of this nanocrystal electrocatalyst system, as a function of ligand coverage, was explored with density functional theory calculations. The Hammett parameter of the surface functional group was found to linearly correlate with the change in Ni and P core-electron binding energies and the nanocrystal’s experimentally and computationally determined work-function. The electrocatalytic activity and stability of the functionalized nanocrystals for hydrogen evolution were also improved when compared to the unfunctionalized material, but a simple trend based on electrostatics was not evident. Density functional theory was used to understand this discrepancy, revealing that H adsorption energies on the covalently functionalized Ni2P also do not follow the electrostatic trend and are predictive descriptors of the experimental results.

scholarly journals Theoretical and Experimental Investigation of the Electronic and Optical Properties of Pure and Interstitial Nitrogen -Doped (TiO2)n Cluster

2021 ◽  
Author(s):  
Shaida Kakil ◽  
Hewa Y Abdullah ◽  
Tahseen G. Abdullah
Keyword(s):  
Photoelectron Spectroscopy ◽  
Density Functional ◽  
Cluster Structure ◽  
Binding Energies ◽  
Vibrational Modes ◽  
Force Microscopy ◽  
Nitrogen Doped ◽  
Quantum Size ◽  
Vis Spectroscopy ◽  
Quantum Espresso

Abstract The structural and electronic properties of pure and nitrogen-doped TiO2 nanoclusters are investigated using density functional theory (DFT) with vibrational modes. We performed numerical simulation using two methods based on theories at the Quantum Espresso/PBE and Gaussian/B3LYP/631G (d) levels. The properties of a single nitrogen-doped (TiO2)n nanocluster are also computed in this study. In both cases, interstitial and substitutional Nitrogen doping at all accessible sites was examined. For the experiment, Supersonic Cluster Beam Deposition (SCBD) was used to create pure and nitrogen-doped TiO2 films of nanocluster assemblies. Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), UV-Vis spectroscopy, and Raman techniques were used to characterize these samples. The binding energies (Np, O2s, Ti 2p1/2, and Ti 2p3/2) of N-doped TiO2 were estimated using XPS spectral results. The UV-Vis measurement confirmed the previously stated reasoning about the quantum size effect on the band gap of the pure and nitrogen doped TiO2 nanocluster. The theoretical vibrational modes frequencies are calculated using the B3LYP/6-31G (d) functional via the Gaussian16 code's implementation algorithm. The good agreement between simulation and experimental results implies that a significant advantage of interstitial over substitutional positions. N-O vibration modes appeared in interstitial doped TiO2, and each vibration was dependent on a different cluster structure.

scholarly journals Mott–Hubbard insulating state for the layered van der Waals $$\hbox {FePX}_3$$ (X: S, Se) as revealed by NEXAFS and resonant photoelectron spectroscopy

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Yichen Jin ◽  
Mouhui Yan ◽  
Tomislav Kremer ◽  
Elena Voloshina ◽  
Yuriy Dedkov
Keyword(s):  
Photoelectron Spectroscopy ◽  
Density Functional ◽  
2D Materials ◽  
Van Der Waals ◽  
Deep Understanding ◽  
Density Functional Theory Calculations ◽  
Binding Energies ◽  
Final State ◽  
Spectroscopy Studies ◽  
Low Dimensional

AbstractA broad family of the nowadays studied low-dimensional systems, including 2D materials, demonstrate many fascinating properties, which however depend on the atomic composition as well as on the system dimensionality. Therefore, the studies of the electronic correlation effects in the new 2D materials is of paramount importance for the understanding of their transport, optical and catalytic properties. Here, by means of electron spectroscopy methods in combination with density functional theory calculations we investigate the electronic structure of a new layered van der Waals $$\hbox {FePX}_3$$ FePX 3 (X: S, Se) materials. Using systematic resonant photoelectron spectroscopy studies we observed strong resonant behavior for the peaks associated with the $$3d^{n-1}$$ 3 d n - 1 final state at low binding energies for these materials. Such observations clearly assign $$\hbox {FePX}_3$$ FePX 3 to the class of Mott–Hubbard type insulators for which the top of the valence band is formed by the hybrid Fe-S/Se electronic states. These observations are important for the deep understanding of this new class of materials and draw perspectives for their further applications in different application areas, like (opto)spintronics and catalysis.

INFLUENCE OF DIANILINE CROSS-LINKING SYSTEMS ON THE STRUCTURE, CURING MECHANISM, AND PROPERTIES OF POLYACRYLICESTER ELASTOMER

2018 ◽  
Vol 91 (4) ◽  
pp. 729-750 ◽  
Author(s):  
Tuhin Saha ◽  
Anil K. Bhowmick ◽  
Takeshi Oda ◽  
Toshiaki Miyauchi ◽  
Nobuhiko Fujii
Keyword(s):  
Mechanical Properties ◽  
Photoelectron Spectroscopy ◽  
High Performance ◽  
Density Functional ◽  
Functional Theory ◽  
Spectroscopic Analyses ◽  
Curing Mechanism ◽  
Temperature Superposition ◽  
Kinetics Of ◽  
Kinetics Of Vulcanization

ABSTRACT To develop high-performance polyacrylicester (ACM) elastomeric components with higher scorch safety and superior thermal and mechanical properties, we replaced aliphatic diamine curatives with aromatic dianiline curatives. The influence of dianiline curatives 4,4′-(4,4′-isopropylidenediphenyl-1,1′-diyldioxy)dianiline, 4,4′-(hexafluoroisopropylidene)bis(p-phenyleneoxy)dianiline, and 4,4′-(1,1′-biphenyl-4,4′-diyldioxy)dianiline on the network structures and thermal, dynamic mechanical, and mechanical properties of ACM vulcanizates was investigated. The kinetics of vulcanization was analyzed for different dianiline curatives, with the use of rheometer curves. To understand the electronic properties and study the relation between chemical structure and reactivity, density functional theory was used. The time–temperature superposition principal was used to evaluate the activation energy for degradation of cross-linked samples. Finally, the curing mechanism of ACM in the presence of dianiline curative was studied with X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. These spectroscopic analyses suggested that the reaction mechanism took place via two steps: the first step was formation of the amide linkage and the second step was formation of imide linkages.

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