Interatomic Charge Transfer Research Articles

Controlling Ultrafast Magnetization Dynamics via Coherent Phonon Excitation in a Ferromagnet Monolayer.

Exploring ultrafast magnetization control in 2D magnets via laser pulses is established, yet the interplay between spin dynamics and the lattice remains underexplored. Utilizing real-time time-dependent density functional theory (rt-TDDFT) coupled with Ehrenfest dynamics and nonadiabatic molecular dynamics (NAMD) simulations, we systematically investigate the laser-induced spin-nuclei dynamics with pre-excited A1g and E2g coherent phonons in the 2D ferromagnet Fe3GeTe2 (FGT) monolayer. Selective pre-excitation of coherent phonons under ultrafast laser irradiation significantly alters the local spin moment of FGT, consequently inducing additional spin loss attributed to the nuclear motion-induced asymmetric interatomic charge transfer. Excited spin-resolved charge undergoes a bidirectional spin-flip between spin-down and spin-up states, characterized by a subtle change in the spin moment within approximately 100 fs, followed by unidirectional spin-flip, which will further contribute to the spin moment loss of FGT within tens of picoseconds. Our results shed light on the coupling of coherent phonons with magnetization dynamics in 2D limit.

Electronic Force Density Fields: Insights into Partial Bonds, Transition States, and Chemical Structure Evolution.

This paper presents the quantum-topological binding approach, in which the electrostatic and total static force density fields, Fes(r) and , together with the electron density gradient field ∇ρ(r), are simultaneously analyzed to elucidate the chemical structure of transition states and the nature of interatomic interactions for semibroken semiformed partial chemical bonds. The approach attributes the discrepancies between the force fields and Fes(r) to the nonclassical electron-electron interaction effects. The internuclear gap between the zero-flux boundaries of Fes(r) and ∇ρ(r) indicates the interatomic charge transfer phenomenon (ICT) that occurs upon the formation of a system from free atoms. Concomitantly, the mismatch of the zero-flux surfaces defined in and ∇ρ(r) can be interpreted as a phenomenon of the electron-transfer-induced quantum chemical response (QCR), which originates from the electron exchange correlation. Our study permits the assertion of parallels between partial bonds and noncovalent interactions, as both typically exhibit incomplete QCRs, indicating the partial electron sharing of the transferred density. The changes in atomic and pseudoatomic charges are employed to describe the evolution of the chemical structure upon the substitution reaction. It is observed that the acquired difference in the actual atomic electronegativity causes polarization upon the heterolytic breaking of virtually nonpolar bonds. It is further proposed that the proximity of closely related stationary states along the reaction path on a potential energy hypersurface implies their similarity in the manifestation of the ICT and sympathetic QCR. Furthermore, the involvement of an electron pair in a partial bond facilitates its delocalization through the attraction by the static forces and Fes(r) to a neighboring nucleus and through the smearing by the Pauli kinetic force FP(r).

Engineering of active site coupling to facilitate interatomic charge transfer for bifunctional oxygen electrocatalysis

Interatomic charge transfer emerges as a robust technique for enhancing catalytic efficacy in key energy reactions, specifically the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Despite its potential, advancing simultaneous improvements in reversible oxygen catalysis pose considerable challenges. Herein, we detailed an active site coupling engineering method to create a CoCu@NSC bifunctional oxygen electrode. In this configuration, OER-active Cu sites were alloyed with ORR-active Co within a N/S-doping carbon nanobox. This arrangement yielded a half-wave potential of 0.924 V for ORR, alongside an overpotential of η10 = 356 mV for OER. The fabricated CoCu@NSC cathode yielded a discharge capacity of 768 mAh/gZn, a peak power density of 295 mW/cm2, and extensive cycling durability. Work function assessments indicated that the chemical integration of Co and Cu components at the atomic level promoted interfacial charge redistribution, effectively optimizing the adsorption-desorption dynamics of intermediates at the active sites, thereby substantially enhancing the catalytic performance for both OER and ORR. Additionally, doping with N/S species enhanced the conductivity of the hollow carbon matrix, facilitating more effective mass and charge transport pathways. These insights illuminate a compelling approach for the design and synthesis of effective bifunctional oxygen electrodes that is pivotal for advanced energy storage advice.

Effect of tensile and compressive strains on the electronic structure of O-atom-doped monolayer MoS2

We investigate the effects of biaxial tensile and compressive strains on the electronic structure of O-doped monolayer MoS2 by density functional theory (DFT) in this paper. O-doped monolayer MoS2 is an exothermic reaction. The doping of O leads to the transformation of the system from direct bandgap to indirect, and the bonding of Mo and O causes a large amount of charge transfer. The application of tensile strain leads to a decrease in the stability of the doped system, and the system always maintains the nature of indirect bandgap. The degree of interatomic charge transfer and bandgap value gradually decrease with the increase of tensile strain. The application of compression strain improves the stability of the doped system, and as the compressive strain increases, the bandgap of the doped system completes the indirect–direct–indirect transformation. The bandgap value shows a trend of increasing and then decreasing. Additionally, the degree of charge transfer between atoms is strengthened.

Carbon Dioxide Electroreduction and Formic Acid Oxidation by Formal Nickel(I) Complexes of Di-isopropylphenyl Bis-iminoacenaphthene.

Processing CO2 into value-added chemicals and fuels stands as one of the most crucial tasks in addressing the global challenge of the greenhouse effect. In this study, we focused on the complex (dpp-bian)NiBr2 (where dpp-bian is di-isopropylphenyl bis-iminoacenaphthene) as a precatalyst for the electrochemical reduction of CO2 into CH4 as the sole product. Cyclic voltammetry results indicate that the realization of a catalytically effective pattern requires the three-electron reduction of (dpp-bian)NiBr2. The chemically reduced complexes [K(THF)6]+[(dpp-bian)Ni(COD)]- and [K(THF)6]+[(dpp-bian)2Ni]- were synthesized and structurally characterized. Analyzing the data from the electron paramagnetic resonance study of the complexes in solutions, along with quantum-chemical calculations, reveals that the spin density is predominantly localized at their metal centers. The superposition of trajectory maps of the electron density gradient vector field and the electrostatic force density field per electron, as well as the atomic charges, discloses that, within the first coordination sphere, the interatomic charge transfer occurs from the metal atom to the ligand atoms and that the complex anions can thus be formally described by the general formulae (dpp-bian)2-Ni+(COD) and (dpp-bian)2 -Ni+. It was also shown that the reduced nickel complexes can be oxidized by formic acid; resulting from this reaction, the two-electron and two-proton addition product dpp-bian-2H is formed.

First‐Principles Study of Schottky Barrier Heights on Metal/4H‐SiC Polar Interfaces

4H‐SiC based devices have garnered significant interest within the realm of high‐voltage and high‐frequency electronic equipment. Schottky barrier heights (SBHs) play a pivotal role in determining the properties of metal/4H‐SiC contacts and holding significance for electrical performance of 4H‐SiC devices. Herein, the first‐principles method is utilized to investigate the interface properties between various metals (Sc, Mg, Zr, Ag, Al, Ru, Rh, Pd, Ni, Au, Ir, and Pt) and 4H‐SiC. The results reveal an approximate linear relationship between SBH and work function of these metals. Fermi‐level pinning factors are determined to be 0.27 and 0.32 for the Si‐face and C‐face interfaces, respectively. The disparity in pinning factors arises from polarization differences between the two interfaces, which stem from uneven net charge distribution on the Si‐face and C‐face. Meanwhile, the SBH values indicate a strong pinning effect, due to the charge transfer occurring at the metal/4H‐SiC interface. Through further analysis of layer density and differential charge density, the interatomic interaction and charge transfer between metal and SiC atoms are analyzed. This work offers fundamental insights into the structural changes in metal/4H‐SiC interfaces and provides valuable guidance in the potential prediction and optimization of device performance.

Adhesion properties of the B- and N-doped graphene/Fe(110) interface

Influence of B and N substitutional impurities on the adhesion properties, electronic and magnetic characteristics of the external and internal graphene/Fe(110) semi-coherent interface was investigated by the projector augmented-wave method within the density functional theory. The analysis of interatomic distances, charge densities, charge transfer and magnetic states of atoms was performed. It was shown that B-doped graphene has a higher adhesion energy on the Fe(110) surface and in the iron bulk in comparison with the undoped systems; whereas, N-doped graphene in the Fe bulk demonstrates the opposite trend and on the surface it has no effect. Boron acts as electron donor that increases charges of the nearest C atoms by 0.5–0.6e. Nitrogen due to its high electronegativity is an acceptor and as a result the nearest C atoms lose 0.2–0.3e. Both impurities, depending on the position, influence differently on the magnetic moment of the nearest iron atoms.

Deciphering non-covalent interactions in unprecedented binuclear copper complex: Spectroscopic, Hirshfeld surface and DFT investigation

Binuclear Cu(II) complex derived from taurine and 2‑hydroxy-4-methoxybenzaldehyde adduct was synthesised and characterised by X-ray crystallography, spectroscopic, Hirshfeld surface and DFT studies. The complex crystallises in monoclinic system with I 2/a space group. A theoretical study of the Cu (II) complex is performed with unrestricted density functional method at the level of B3LYP/ LANL2DZ/6–311 G (d, p) and a comparison between the experimental and simulated results were conducted. As predicted by the experiment, the computed results support distorted pyramidal geometry at metal centre. Non-covalent interactions primarily H-bonding and π-π stacking close contacts were observed at the intramolecular and intermolecular levels of the complex. An analysis of the FMO parameters reveals less reactivity and stability of complex. A high HOMO energy value and interatomic charge transfer has taken place with the Schiff base ligand. Furthermore, MEP used for predicting reactive sites clearly shows this complex is void of electrophilic reaction site. This complex has been subjected to NBO analysis to determine its hyperconjugation and therefore stability. The NBO analysis revealed the delocalization of charge within the molecule. Based on Hirshfeld surface analysis, there is evidence for a wide range of interactions and a significant contribution from several non-covalent interactions to crystal packing.

A combined theoretical and experimental study of nickel derivative [Daiquiris(nicotinamide-jN1)nickel (II)]-lfumarato-K2O1:O4

The ground state geometry of the nickel derivative [Daiquiris(nicotinamide-jN1) nickel(II)]-fumarato-K2O1:O4 has been optimized and is being led toward its quantum chemical analysis in this paper. For more accuracy, we used the 6-311[Formula: see text]G (d, p) basis set for C, H, N, and O atoms and the LAN2DZ basis set for Ni. The calculated and experimental infrared (IR) spectra for the title molecule are well correlated, and the correlation factor [Formula: see text] shows that the method effectively interprets the molecule’s IR spectra. The electronic properties such as highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies and associated energy gap have been calculated by Time-Dependent Density Functional Theory (TD-DFT) approach. The natural bond orbital (NBO) analysis of the molecule describes how interatomic charge transfer results in the formation of bonding–nonbonding interactions. The experimental and calculated Ultraviolet visible (UV-Vis) spectra are compared. We anticipate our work will inspire fresh approaches to the title molecule’s ongoing research.

Applicability of transferable multipole pseudo-atoms for restoring inner-crystal electronic force density fields. Chemical bonding and binding features in the crystal and dimer of 1,3-bis(2-hydroxyethyl)-6-methyluracil.

We considered it timely to test the applicability of transferable multipole pseudo-atoms for restoring inner-crystal electronic force density fields. The procedure was carried out on the crystal of 1,3-bis(2-hydroxyethyl)-6-methyluracil, and some derived properties of the scalar potential and vector force fields were compared with those obtained from the experimental multipole model and from the aspherical pseudo-atom model with parameters fitted to the calculated structure factors. The procedure was shown to accurately replicate the general vector-field behavior, the peculiarities of the quantum potentials and the characteristics of the force-field pseudoatoms, such as charge, shape and volume, as well as to reproduce the relative arrangement of atomic and pseudoatomic zero-flux surfaces along internuclear regions. It was found that, in addition to the quantum-topological atoms, the force-field pseudoatoms are spatially reproduced within a single structural fragment and similar environment. In addition, the classical and nonclassical hydrogen bonds in the uracil derivative crystal, as well as the H...O, N...O and N...C interactions in the free π-stacked dimer of the uracil derivative molecules, were studied using the potential and force fields within the concepts of interatomic charge transfer and electron lone pair donation-acceptance. Remarkably, the nitrogen atoms in the N...O and N...C interactions behave rather like a Lewis base and an electron contributor. At the same time, the hydrogen atom in the H...O interaction, being a Lewis acid, also participates in the interatomic electron transfer by acting as a contributor. Thus, it has been argued that, when describing polar interatomic interactions within orbital-free considerations, it makes more physical sense to identify electronegative (electron occupier) and electropositive (electron contributor) atoms or subatomic fragments rather than nucleophilic and electrophilic sites.

Domain-limited growth strategy to construct Fe3C@C@CNTs heterogeneous interfaces for multi-functional high-performance lithium-ion storage and microwave absorption

Rational designed cost-effective material is significant in the field of electric energy storage and microwave absorber. In this work, carbon coated Fe3C nanoparticles (NPs) encapsulated carbon nanotubes (Fe3C@C@CNTs) is delicately constructed through in-situ chemical vapor deposition (CVD) strategy. As a promising anode material for lithium-ion batteries (LIBs), the Fe3C@C@CNTs nanocomposite facilitates electron transport with intensive interfacial interaction, making it an ideal prototype to thoroughly understand the mechanisms of interatomic charge transfer mechanism. As a result, this well-designed Fe3C@C@CNTs anode exhibits a high reversible capacity of 1027 mAh g−1 after 150 cycles at 0.1 A g−1 and excellent cycling stability with 71 % capacity retention at 519 mAh g−1 after 1000 cycles at 1.0 A g−1. Electrochemical kinetic results confirm that the pseudocapacitance contributions reach up to 90.1 % at 1.0 mV s−1, and the higher pseudocapacitance characteristic is ascribed to the multi-dimensional encapsulated by CNT layer and carbon layer. Meanwhile, depending on the peculiar cavity structure and heterogeneous interfaces effects constructed by multi-dimensional encapsulated structure, the minimum reflection loss (RLmin) of Fe3C@C@CNTs nanocomposite can reach up to −67.63 dB in effective absorption bandwidth (EAB) of 7.12 GHz with the optimal matching thickness of 2.28 mm, suggesting its extensive potential application as practical alternative absorber. This domain-limited growth strategy opens a new horizon to achieve multi-functional application and beyond for Fe-based nanomaterial.

Curtailing the Excess eg-Orbital Filling of a Ni Atom by Enhanced Interatomic Charge Transfer within a Bimetallic 2D Metal–Organic Framework for the Oxygen Evolution Reaction

Electrochemical conversion technologies rely on the design and creation of highly efficient electrocatalysts. The oxygen evolution reaction (OER), which has applications in water splitting and metal–air batteries, is a crucial process in such conversions. Herein, a bimetallic Co, Ni-based ultrathin metal–organic framework nanoribbon (NiCo-NR) is reported for an efficient OER. It is proposed that in ultrathin MOF nanoribbons, the surface atoms (Co, Ni) are coordinatively unsaturated, due to which the interatomic electron transfer within the MOF makes more active adsorption sites on the surface. The catalyst exhibits an overpotential of 244 mV at a current density of 10 mA cm–2 with a Tafel slope value of 85 mV dec–1. For the stability experiment, the catalyst was exposed for 35 h of uninterrupted operation at a current density of 100 mA cm–2. Our findings showed that coordinatively unsaturated transition metal atoms were dominant active sites and the electrocatalytic activity can be tuned by the coupling interactions of Ni and Co metals. The excess eg-orbital filling of the Ni atom, which limits the electrocatalytic performance, can be reduced by π-donation from Ni to Co through the oxygen atom.

Electronic and Crystal Packing Effects in Terms of Static and Kinetic Force Field Features: Picolinic Acid N-Oxide and Methimazole

Herein, we experimentally obtained and studied the inner-crystal scalar potential fields and the associated vector force fields of static and kinetic nature in picolinic acid N-oxide (PANO) and methimazole. The “through-bond” and “through-space” electronic effects were defined and distinguished via the vector fields and concurred with the penetration of the electron contributor’s electrostatic and kinetic force field pseudoatoms (φes- and φk-basins) into the occupier’s chemical atom (ρ-basin). A special focus was given to the dipolar N+–O– bond as well as to the thioamide N–C═S and carboxylic O═C–OH fragments. An unusual way of interatomic charge transfer was revealed between two nonbonded hydrogen atoms [COO−]H···H[−C] in the PANO crystal. The experimental electric and kinetic force fields in the molecular crystals were compared to the theoretical ones for the free molecules and hydrogen-bonded associates, which helped figure out the natural consequences of the crystal packing effect. As expected, the appearance of neighboring attractors in a dense crystal packing requires zero-flux surfaces (ZFSs) emerging in the vector fields and the compression of the outer force field pseudoatoms of a molecule. We proposed to consider a ZFS in the kinetic force field to be a turning surface for electrons in the sense that an electron passed through the boundary is immediately affected by the redirected force attributed to another attractor. The strengthening and noticeable increase observed in the covalency of the intramolecular hydrogen bond O–H···O in the PANO crystal is a direct consequence of such compression of the hydrogen atom and pseudoatoms by the inner-crystal environment. The Pauli and fermionic scalar and vector fields were applied to locate electron lone pairs and describe their involvement in noncovalent interactions within the donor–acceptor mechanism.

Real-Space Interpretation of Interatomic Charge Transfer and Electron Exchange Effects by Combining Static and Kinetic Potentials and Associated Vector Fields.

Intricate behaviour of one-electron potentials from the Euler equation for electron density and corresponding gradient force fields in crystals was studied. Channels of locally enhanced kinetic potential and corresponding saddle Lagrange points were found between chemically bonded atoms. Superposition of electrostatic and kinetic potentials and electron density allowed partitioning any molecules and crystals into atomic - and potential-based -basins; -basins explicitly account for the electron exchange effect, which is missed for -ones. Phenomena of interatomic charge transfer and related electron exchange were explained in terms of space gaps between zero-flux surfaces of - and -basins. The gap between - and -basins represents the charge transfer, while the gap between - and -basins is a real-space manifestation of sharing the transferred electrons caused by the static exchange and kinetic effects as a response against the electron transfer. The regularity describing relative positions of -, -, and - basin boundaries between interacting atoms was proposed. The position of -boundary between - and -ones within an electron occupier atom determines the extent of transferred electron sharing. The stronger an H⋅⋅⋅O hydrogen bond is, the deeper hydrogen atom's -basin penetrates oxygen atom's -basin, while for covalent bonds a -boundary closely approaches a -one indicating almost complete sharing of the transferred electrons. In the case of ionic bonds, the same region corresponds to electron pairing within the -basin of an electron occupier atom.

Mo-O-Bi Bonds as interfacial electron transport bridges to fuel CO2 photoreduction via in-situ reconstruction of black Bi2MoO6/BiO2-x heterojunction

High photogenerated carrier separation efficiency plays a crucial role in determining the rate of photocatalytic CO2 reduction, but the directional transfer of carrier remains challenging. Here, improved CO2 photoreduction rate and enhanced stability were realized by in-situ construction of BiO2-x nanoparticles on Bi2MoO6 nanoflowers using H2/Ar low temperature plasma. As evidenced by DFT calculations and photocurrent measurements, the Mo-O-Bi bonds between the Bi2MoO6 and BiO2-x interfaces act as a charge transport bridge, facilitating the directional transport of electrons and thus enhancing the rate of photocatalytic reduction reactions involving multiple electrons. Compared with pristine Bi2MoO6, Bi2MoO6/BiO2-x heterojunction has excellent photostability (12 h) and efficient photocatalytic activity (≈ 3.0 times). This indicates that the charge transfer bridge can effectively inhibit the charge recombination and deactivation of pristine Bi2MoO6. This interatomic charge transfer bridges mode can not only solve the stability problem of bismuth-based materials, but also help to design more photocatalytic systems for efficient reduction of CO2.

Core electron spectroscopic studies on new structure type iron based superconductors CaKFe4As4 and KCa2Fe4As4F2: DFT predictions

Theoretical predictions on X-ray absorption near edge structure (XANES) for two different newly discovered hybrid iron-based superconducting compounds, CaKFe4As4 and KCa2Fe4As4F2, are presented. The Fe and As K-edge absorption spectra of these hybrid compounds as well as their parent building block materials KFe2As2, CaFe2As2, and CaFeAsF are theoretically calculated and contrasted with each other. In particular, for the hybrid compounds, As K-edge absorption spectra are qualitatively different for two distinct types of As atoms belonging to dissimilar coordination environments. No such differences are found in the XANES of the building block compounds, in which all of the As atoms belong to an equivalent coordination environment. Our density functional theory-based first principles studies in the presence and absence of the core-hole effect are presented separately, to understand the role of the core-hole effect in determining the XANES for these compounds. In general, the core-hole effect is most significant in CaKFe4As4 compared to the other compounds, for which its effect is moderate. The distinct peak features of the absorption spectra signify specific electronic transitions, which are thoroughly explained in terms of the unoccupied atom projected partial density of states. Very prominent pre-edge features found in KFe2As2, CaFeAsF, and CaKFe4As4 imply perfect tetrahedral coordination of the absorbing Fe atom in these compounds, while this is slightly distorted in CaFe2As2 and KCa2Fe4As4F2. The interrelationship between the inter-atomic charge transfer and the shift in the Fe K-edge absorption for various compounds is established through Bader charge analysis. We find that the Fe atom transfers relatively less charge in the case of KFe2As2 compared to KCa2Fe4As4F2, which shifts the corresponding absorption edge of KCa2Fe4As4F2 to higher photon energy.

Changes in the spectroelectrochemical properties of copper(II) hexacyanoferrate(III) during electrochemical insertion of alkaline ions

In this work, the influence of the electrochemical insertion of different alkali ions, e.g., lithium, sodium, and potassium, on the electrochromic properties of copper(II) hexacyanoferrate(III) (CuHCF) was addressed. CuHCF was electrochemically synthesized on FTO substrates, and a nucleation and growth analysis was shown that follows a 3D progressive nucleation with diffusion-controlled growth, which was confirmed by SEM analysis. The spectroelectrochemical study demonstrated that spectral changes were centered into three regions: a green band (506 nm) associated with a charge transfer (FeIII → CuII), a violet band (413 nm) associated with d-d orbital transition for Cu+2 ions, and an ultraviolet band (354 nm) associated with a ligand-metal charge transfer (CN-→ FeIII). This electronic transfer, along with the calculated electrochromic efficiency averages, indicates a relationship between the ionic radius of insertion ions and the deformation generated in CuHCF. An increase in the ionic radius decreases the interatomic charge transfer, which produces a low electrochromic efficiency.

Orbital-Free Quantum Crystallographic View on Noncovalent Bonding: Insights into Hydrogen Bonds, π⋅⋅⋅π and Reverse Electron Lone Pair⋅⋅⋅π Interactions.

A detailed analysis of a complete set of the local potentials that appear in the Euler equation for electron density is carried out for noncovalent interactions in the crystal of a uracil derivative using experimental X-ray charge density. The interplay between the quantum theory of atoms in molecules and crystals and the local potentials and corresponding inner-crystal electronic forces of electrostatic and kinetic origin is explored. Partitioning of crystal space into atomic basins and atomic-like potential basins led us to the definite description of interatomic interaction and charge transfer. Novel physically grounded bonding descriptors derived within the orbital-free quantum crystallography provided the detailed examination of π-stacking and intricate C=O⋅⋅⋅π interactions and nonclassical hydrogen bonds present in the crystal. The donor-acceptor character of these interactions is revealed by analysis of Pauli and von Weizsäcker potentials together with well-known functions, e. g., deformation electron density and electron localization function. In this way, our analysis throws light on aspects of these closed-shell interactions hitherto hidden from the description.

Out-of-plane ionicity versus in-plane covalency interplay and electron–phonon coupling in MgB2 superconductor

Using the Density Functional Theory (DFT) within the Generalized Gradient Approximation (GGA) pseudopotential and plane wave basis method along with the frozen-phonon approach that starts from the ab initio evaluation of the total energy Etot of the solid with frozen-in atomic displacements, it is found that a superposition of A2u and the E2gvibrations modes is the key factor in the superconducting mechanism in MgB2 compound. Electron–Phonon coupling to these A2u and E2g phonon modes especially at the zone-boundary A point of the hexagonal Brilliouin zone leads to an interband hole charge transfer (and transfer back) between in-plane σ bond to the out-of-plane π bond along with an interatomic electron charge transfer (and transfer back) between the Magnesium s-states to the Boron out-of-plane pz-state. The direction of the electronic current is opposite to that of hole current so that it reinforces the polarization associated with these currents and may generate a large dynamical charge at a given critical temperature Tc that drives the compound into the superconducting state.

Valence charge distribution in homogenous silicon-aluminium thin-films

Homogenous aSi1−xAlxHy alloyed thin films, made by magnetron sputtering, has been found to exhibit tunable band gap and dielectric constant depending on their composition. The optical properties of alloys are largely defined by their electronic structure, which is is strongly influenced by interatomic charge transfer. In this work we have quantified interatomic charge transfer between Si, Al and H in aSi1−xAlxHy thin-films, with and . Charge transfer was found experimentally using x-ray photoelectron spectroscopy, by incorporating Auger parameter data into the Thomas and Weightman model. Both the perfect and imperfect screening models were tested, and the results were compared to models calculated using density functional theory based molecular dynamics. Using imperfect screening properties of Si and Al resulted in an excellent agreement between the experimental and computational results. Alloying aSi with Al is associated with donation of electrons from Al to Si for y = 0. For y > 0 electrons are transferred away from both Al and Si. The change in Si valence charge increases linearly with increasing band gap and decreasing dielectric constant. These relationships can be used as a quick guide for the evaluation of the Si valence charge and subsequently optoelectronic properties, at specific Al/Si ratios.