Electronic Density Of States Research Articles

EFFECT OF Rh-DOPING ON THE OPTICAL ABSORPTION OF THE (001) BaTiO<sub>3</sub> SURFACE

Barium titanate is one of the most studied perovskite materials due to its substitution ability at both nodes of the crystal lattice, high dielectric constant, and stability. It has many outstanding characteristics, especially ferroelectric and dielectric properties, which can be improved by alloying, making this material suitable for a wide range of applications. In this paper, the effect of Rh doping on the structural, optical properties and electronic density of states of this compound is investigated. According to our calculations, Rh doping is a method that helps to increase the ability of BaTiO3 to absorb more light and reduce the excess potential required for water oxidation. Calculations of the electronic density of states were carried out using the hybrid functional HSE06. The analysis of optical properties was performed on the basis of matrix elements with a transient dipole moment. Studies have confirmed that the (001) BaTiO3 surface with terminated TiO2 has significant potential for use as a catalyst. Rh doping leads to an expansion of the spectrum of absorbed light over the entire visible range.

Energy‐saving hydrogen production by heteroatom modulations coupling urea electrooxidation

AbstractDeveloping efficient electrocatalysts with low‐cost for the urea oxidation reaction (UOR) is a significant challenge in energy‐saving H2 production owing to its lower thermodynamic potential. Heteroatom incorporation strategy has been proven to boost electrocatalytic activity by altering electronic structures and revealing more active sites on catalysts. Herein, nickel hydroxide nanosheets with various vanadium incorporation (Vx‐Ni(OH)2) were developed through a facile hydrothermal approach. By optimizing the incorporated vanadium contents, V6‐Ni(OH)2 catalyst exhibited easily accessible active sites and enhanced charge transfer with structural advantages, then assembled as the working electrode for urea‐assisted H2 production. Consequently, V6‐Ni(OH)2 catalyst demonstrated superior UOR activity compared with other incorporated samples with an overpotential of 1.33 V and a Tafel slope of 28.3 mV dec−1. Theoretical calculations revealed that the improved UOR activity was attributed to the potential determining step of V‐Ni(OH)2, which exhibited lower energy in comparison with the pristine Ni(OH)2 and increased electronic states density near the Fermi level. Both experimental and theoretical calculations confirmed vanadium incorporation on Ni(OH)2 could modify the electronic structure of Ni(III) species, improving electrical conductivity, and optimizing the adsorption energy for key reaction intermediates. Furthermore, the crucial contribution of vanadium incorporation with optimized electronic structures to the high UOR activity of Ni(OH)2 is demonstrated.image

Structure, bonding, and properties of RCr6Ge6 intermetallics (R[dbnd]Gd–Lu)

We report the discovery and characterization of three novel ternary compounds: TmCr6Ge6, YbCr6Ge6, and LuCr6Ge6, which complete the series of RCr6Ge6 intermetallics with kagome lattice. Energy dispersive X-ray analysis revealed the off-stoichiometric composition of RCr6Ge6 (RGd, Tb, Dy, Ho, Er, Tm, Yb, and Lu). The powder XRD analysis with subsequent Rietveld refinement showed that investigated compounds crystallize in the SmMn6Sn6 structure type (space group P6/mmm), a disordered variant of the MgFe6Ge6-type, with a small number of vacancies at the rare earth (1a) and germanium (2e) sites and two additional 1b and 2e sites partially occupied by additional rare earth and germanium atoms, respectively. A tendency to structure ordering is observed with decreasing rare earth ionic radii. Electrical resistivity measurements indicate a metallic conductivity type for all studied compounds. Magnetic characterization reveals paramagnetic behavior for TmCr6Ge6 and LuCr6Ge6, respectively, and suggests YbCr6Ge6 as a ferrimagnetic material. The DFT modeling of RCr6Ge6 shows a distinct high electron localization between Ge1 atoms, corresponding to strong covalent bonding. The calculated enthalpies of formation range from −18.56 kJ/mol for Gd to −19.60 for Tm compounds, while the distribution of the density of electronic states (DOS) confirms the metallic type of conductivity for all the series. The calculated elastic properties show brittle behavior and a high hardness level for the whole series. DFT modeling allowed us to reveal mechanisms of RCr6Ge6 formation and the origin of disorder in their crystal structure.

Intrinsic Limits of Charge Carrier Mobilities in Layered Halide Perovskites

Layered halide perovskites have emerged as potential alternatives to three-dimensional (3D) halide perovskites due to their improved stability and larger material phase space, allowing fine tuning of structural, electronic, and optical properties. However, their charge carrier mobilities are significantly smaller than those of 3D halide perovskites, which has a considerable impact on their application in optoelectronic devices. Here, we employ state-of-the-art approaches to unveil the electron-phonon mechanisms responsible for the diminished transport properties of layered halide perovskites. Starting from a prototypical AMX3 halide perovskite, we model the case of n=1 and n=2 layered structures and compare their electronic and transport properties to the 3D reference. The electronic and phononic properties are investigated within density functional theory (DFT) and density functional perturbation theory (DFPT), while transport properties are obtained via the Boltzmann transport equation. The vibrational modes contributing to charge carrier scattering are investigated and associated with polar-phonon scattering mechanisms arising from the long-range Fröhlich coupling and deformation-potential scattering processes. Our investigation reveals that the lower mobilities in layered systems primarily originate from the increased electronic density of states at the vicinity of the band edges, while the electron-phonon coupling strength remains similar. Such an increase is caused by the dimensionality reduction and the break in octahedra connectivity along the stacking direction. Our findings provide a fundamental understanding of the electron-phonon coupling mechanisms in layered perovskites and highlight the intrinsic limitations of the charge carrier transport in these materials. Published by the American Physical Society 2024

Studying supercapacitance and thermoelectric performance of semiconductor BaTiO[formula omitted] along with its halfmetal alloy of BaTiFO[formula omitted]: A DFT+U investigation

In the present work, the electrical, supercapacitance, and thermoelectric properties of BaTiO3 semiconductor perovskite and its alloy with F atoms (in replacement of one of the O atoms) have been investigated using density functional theory and implementing general gradient approximation by considering Hubbard’s potential (U). The electronic density of state results for the BaTiO3 exhibit energy band gaps of 1.833 and 2.143 eV without and with considering U, respectively. Moreover, by implementing the F atom and because of the existence of Ti atoms in the compound the ferromagnetic property appeared in the alloy compound with the total magnetization of 0.97 Bohr mag/cell. The halfmetallic behavior emerged in the alloy compound by using GGA+U and the spin down showed an energy band gap of 3.32 eV while the spin up exhibited metallic properties. Furthermore, the most significant peak of the areal quantum capacitance was 871.71 μF/cm2 for BaTiO3 by the GGA method, and by considering U it was 765.78 μF/cm2. In addition, the most prominent peak of thermoelectric power factor per relaxation time at room temperature belonged to BaTiO3 with a value of 42.05 × 1016μW m−1 s−1 K−2 with considering U, and without considering U, it was 34.7 × 1016μW m−1 s−1 K−2.

First-principles study of electronic, mechanical, and optical properties of M3GaB2 (M = Ti, Hf) MAX phases

Integrating ceramic and metallic properties in MAX phases makes them highly desirable for diverse technological applications. In this study, through first-principles density functional theory (DFT), we investigated the physical properties of two new 312 MAX compounds, M3GaB2 (M = Ti, Hf). Chemical stability is confirmed via formation energy assessment, while mechanical stability is established by determining elastic stiffness constants. A thorough analysis of mechanical behaviors includes bulk modulus, shear modulus, Young's modulus, and hardness parameters. M3GaB2 demonstrates elastic constants and moduli closely aligned with other 312 carbides. Understanding the electronic band structure and density of states (DOS) sheds light on metallic properties, with anisotropy in electrical conductivity clarified through energy dispersion analysis. Investigation of photon interaction with titled compounds, including dielectric constants (real and imaginary parts), refractive index, absorption coefficient, photoconductivity, reflectivity, and energy loss function, has been carried out. The potential of M3GaB2 borides as a coating to reduce solar is evaluated based on the reflectivity spectra. These findings deepen our understanding of material properties and suggest diverse applications for M3GaB2 in various technological domains.

Ab-initio insights into the mechanical, phonon, bonding, electronic, optical and thermal properties of hexagonal W2N3 for prospective applications

We thoroughly investigated the structural, mechanical, electronic, vibrational, optical, thermodynamic, and a number of thermophysical properties of W2N3 compound through first-principles calculations using the DFT based formalism. The calculated structural parameters show very good agreement with the available theoretical and experimental results. The mechanical and dynamical stabilities of this compound have been investigated theoretically from the elastic constants and phonon dispersion curves. The Pugh's and Poisson's ratios of W2N3 are located quite close to the brittle/ductile borderline. W2N3 is elastically anisotropic. The calculated electronic band structure and density of states reveal that W2N3 is conducting in nature. The Fermi surface topology has also been explored. The analysis of charge density distribution map shows that W atoms have comparatively high electron density around compared to the N atoms. Presence of covalent bondings between W–N, W–W, and N–N atoms are anticipated. High melting temperature and high phonon thermal conductivity of W2N3 imply that the compound has potential to be used as a heat sink system. The optical characteristics show anisotropy. The compound can be used in optoelectronic devices due to its high absorption coefficient and low reflectivity in the visible to ultraviolet spectrum. Furthermore, the quasi-harmonic Debye model is used to examine temperature and pressure dependent thermal characteristics of W2N3 for the first time.

Structural, electronic, and optical properties of ferroelectric hybrid (Me[formula omitted]NH[formula omitted])[NaFe(CN)[formula omitted](NO)] crystal: Density functional theory simulation

Utilizing density functional theory (DFT), we embarked on a comprehensive investigation of the structural, electronic, and optical properties characteristic of the ferroelectric hybrid (Me2NH2)[NaFe(CN)5(NO)] crystal. The geometry of the crystal structure in the Pna21 phase was optimized. We simulated the electronic band structure within the first Brillouin zone. The calculated band gap for the indirect U-X transition is 2.401 eV, indicative of a wide band gap semiconductors. We also simulated the density of electronic states across the Brillouin zone. The simulation of the electronic structure revealed that the crystal comprises both ionic and covalent bonds. We accurately predicted various optical parameters including the dielectric function, conductivity, reflectivity, loss function, absorption, and refractive index. The reflectivity of the crystal does not exceed 21 percent. All calculated optical properties of the (Me2NH2)[NaFe(CN)5(NO)] crystal are anisotropic.

Bifunctional Strontium Cobalt Molybdenum Oxide (Sr2CoMoO6) Perovskite as an Efficient Catalyst for Electrochemical Water Splitting Reactions in Alkaline Media

AbstractDeveloping earth‐abundant low‐cost electrocatalysts is of prime research interest towards the need for clean energy technology, such as water‐splitting reactions. Herein, we have explored the electrocatalytic activity of the double perovskite‐based strontium cobalt molybdenum oxide (SCMO) towards water‐splitting reactions, both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), in harsh alkaline condition (1 M KOH). Prepared by scalable autocombustion synthesis, the as‐synthesised bulk SCMO perovskite exhibited impressive electrocatalytic performance attributed to its substantial electrochemical active surface area, measured at 26.3 cm2. For the OER, it exhibited an overpotential of 350 mV with a Tafel slope value of 76 mV/dec. Concurrently, it showed proficient activity in the HER, revealing an overpotential of 270 mV and a Tafel slope of 112 mV/dec. Further, this perovskite material was stable during continuous electrocatalysis over a 24 h period in harsh alkaline media with a negligible increase in observed overpotential value. The electronic density of states confirmed that the Co plays a pivotal role in enhancing electrocatalytic activities. This is achieved by a substantial reduction in the band gap and enhancement of the d‐band centre to an optimal level, rendering the system more favourable for electrocatalytic reactions. Our study contributes essential insights to the advancement of the design and utilization of perovskite‐based catalysts in the realm of sustainable energy technologies.

Theoretical study of alkali metals (Li, Na, K) intercalation in the H2Ti3O7(1 0 0) surface

The H2Ti3O7 system has potential to be applied as a Li/Na/K-ion battery anode material. It is relevant to theoretically study the (100) nanosheet of this material since there are no studies regarding intercalation of Li/Na/K in it. Density Functional Theory calculations with the Hubbard methodology (DFT + U) were conducted in order to find and test several intercalation sites for the three different metals, finding stability and high voltages in all of them. Moreover, the electronic density of states confirms the stability of the systems and charge transfer studies were performed to compare the electron transfer between the most stable sites of each intercalated metal and the surface. Nudged Elastic Band (NEB) calculations were performed, finding lower barriers of 0.54 eV and 0.41 eV for Li and Na diffusion. This study shows that this material is promising and can be a guide for future works.

Adsorption mechanisms of heavy metal atoms As, Pb, and Zn on thermally activated palygorskite Si–O/Mg–O (200) surfaces: A first-principles calculations

Heavy metal pollution on air, water, and soil is an issue of increasing global concern. Adsorption is widely recognized as one of the most effective methods for removing heavy metal pollution. The adsorption mechanisms of As (Arsenic), Pb (Lead), and Zn (Zinc) atoms on thermally activated palygorskite Si–O (200) and Mg–O (200) surfaces were investigated using first-principles calculations based on DFT. The coverage dependence of the adsorption configurations and energies on the most stable adsorption sites was also analyzed. The bridge site was found to be the most stable adsorption site for As and Pb on the Si–O (200) surface, while the adsorption energy of Zn was ＜ 0.1 eV on the surface. The adsorption capacity order of the surface was As > Pb ≫ Zn. On the Mg–O (200) surface, the hollow site was the most stable site for three heavy metal atoms. The adsorption energies of them gradually decreased with increasing coverage, thus indicating the lower stability of surface adsorption due to the repulsion of neighboring heavy metal atoms. The adsorption capacity of the Mg–O (200) surface followed the order of As > Pb > Zn. Further exploration was performed on the changes in structure and electronic properties within the adsorption process by studying the lattice relaxation, Bader charge, and electronic density of states (DOS) of the thermally activated palygorskite (200)/heavy metal atoms system.

Thermoelectric performance of Ag2GeX3 (X = S, Se, Te) with intrinsically low lattice thermal conductivity: A first principles study

Low lattice thermal conductivity is one of the key factor for excellent thermoelectric performance of materials. In this work, we have systematically studied the thermoelectric properties of Ag2GeX3 (X = S, Se, Te) by first-principles calculations in combination with Boltzmann transport theory. In terms of phonon transmission performance, due to the low frequency of acoustic phonons, strong coupling between low-frequency optical phonons and acoustic phonons, and relatively strong anharmonicity, Ag2GeX3 (X = S, Se, Te) exhibits extremely low lattice thermal conductivity of 0.30 Wm−1K−1, 0.28 Wm−1K−1 and 0.65 Wm−1K−1 at room temperature, respectively. At the same time, Ag2GeX3 (X = S, Se, Te) also exhibits good electrical transport performance. The appropriate band gap and high slope of electronic density of states (DOS) near the Fermi level result in a large Seebeck coefficient of the materials. As a result, the optimal ZT values of p(n)-type Ag2GeX3 (X = S, Se, Te) are 1.4(1.2), 2.2(0.7), and 0.9(0.7) at 800 K, respectively. These results demonstrate outstanding thermoelectric performance of Ag2GeSe3 for energy conversion applications.

On Chemical Bonding in ht-Ga3Rh and Its Effect on Structural Organization and Thermoelectric Behavior.

In the course of systematic studies of intermetallic compounds Ga3TM (TM─transition metal), the compound Ga3Rh is synthesized by direct reaction of the elements at 700 °C. The material obtained is characterized as a high-temperature modification of Ga3Rh. Powder and single-crystal X-ray diffraction analyses reveal tetragonal symmetry (space group P42/mnm, No. 146) with a = 6.4808(2) Å and c = 6.5267(2) Å. Large values and strong anisotropy of the atomic displacement parameters of Ga atoms indicate essential disorder in the crystal structure. A split-position technique is applied to describe the real crystal structure of ht-Ga3Rh. Bonding analysis in ht-Ga3Rh performed on ordered models with the space groups P1̅, P42nm, and P42212 shows, besides the omnipresent heteroatomic Ga-Rh bonds in the rhombic prisms ∞3[Ga8/2Rh2], the formation of homoatomic Ga-Ga bonds bridging the Rh-Rh contacts and the absence of significant Rh-Rh bonding. These features are essential reasons for the experimentally observed disorder in the lattice. In agreement with the calculated electronic density of states, ht-Ga3Rh shows temperature-dependent electrical resistivity of a "bad metal". The very low lattice thermal conductivity of less than 0.5 W m-1 K-1 at 300 K, being lower than those for most other Ga3TM compounds, correlates with the enhanced bonding complexity.

Theoretical analysis of magnetic, optoelectronic, and thermoelectric properties of Cs2CuCrX6 (X = Cl and Br) double perovskites for spintronic and data storage devices

Spintronics is an emerging field that has the potential to replace conventional electronics due to their comparatively high speed, low power consumption, and infinite endurance. The phenomena of ferromagnetism with high spin polarization in double perovskites make them the desired materials for spintronics. In the present work, the structure of Cs2CuCrX6 (X = Cl and Br) and their magnetic and optoelectronic properties were studied by utilizing density functional theory (DFT). For the calculations of exchange-correlation potential, PBE-sol approximation was utilized while for the accurate measurement of electronic band structure and density of states (DOS), we employed mBJ potential. Both materials exhibit cubic structure and are thermodynamically stable as confirmed by volume optimization and negative formation energy respectively. Spin-based energy-volume optimization and values of exchange constants reveal the ferromagnetic nature of materials. It has been observed that 3-d states of Cr are responsible for ferromagnetism and have the major contribution to the net magnetic moment caused by exchange splitting. Furthermore, investigations of band structure and electronic density of states showed that both Cs2CuCrCl6 and Cs2CuCrBr6 were indirect bandgap (Eg) semiconductors with the Eg values of 1.2 eV and 0.33 eV respectively. The optical spectra of materials showed strong absorption in the ultraviolet region. Lastly, the transport and thermoelectric properties (TE) of materials were investigated in the range of temperature 300 K–800 K by using the BoltzTrap code. The transport parameter which included the electrical conductivity (σ/τ) and thermal conductivity (κe/τ) of the materials showed a decreasing trend with temperature whereas the Seebeck coefficient (S) and Power factor (P.F) showed an increasing trend for Cs2CuCrCl6 while decreases in case of Cs2CuCrBr6. Furthermore, a high figure of merit (ZT) with values of 0.75 and 0.64 was obtained for Cs2CuCrCl6 and Cs2CuCrBr6 respectively. The results of this work are encouraging and show the capabilities of the discussed materials in the fields of spintronics, thermoelectric, and optoelectronics.

Ce3Bi4Ni3 – A large hybridization-gap variant of Ce3Bi4Pt3

The family of cubic noncentrosymmetric 3-4-3 compounds has become a fertile ground for the discovery of novel correlated metallic and insulating phases. Here, we report the synthesis of a new heavy fermion compound, Ce3Bi4Ni3. It is an isoelectronic analog of the prototypical Kondo insulator Ce3Bi4Pt3 and of the recently discovered Weyl-Kondo semimetal Ce3Bi4Pd3. In contrast to the volume-preserving Pt-Pd substitution, structural and chemical analyses reveal a positive chemical pressure effect in Ce3Bi4Ni3 relative to its heavier counterparts. Based on the results of electrical resistivity, Hall effect, magnetic susceptibility, and specific heat measurements, we identify an energy gap of 65–70 meV, about eight times larger than that in Ce3Bi4Pt3 and about 45 times larger than that of the Kondo-insulating background hosting the Weyl nodes in Ce3Bi4Pd3. We show that this gap as well as other physical properties do not evolve monotonically with increasing atomic number, i.e., in the sequence Ce3Bi4Ni3−Ce3Bi4Pd3−Ce3Bi4Pt3, but instead with increasing partial electronic density of states of the d orbitals at the Fermi energy. This work opens the possibility to investigate the conditions under which topological states develop in this series of strongly correlated 3-4-3 materials. Published by the American Physical Society 2024

Prediction of electronic density of states in guanine-TiO2 adsorption model based on machine learning

The electronic density of states is a property of the material that is extensively used in quantum systems in condensed matter physics. It refers to the energy level of the electrons in a solid crystal. One of the most current ways to compute it is by Density Functional Tight Binding (DFTB), given the geometry of the material. Nevertheless, this computation could be very computationally demanding, although applied to some materials with a very reduced number of atoms. This paper presents a method to deduce the electronic density of states, which is based on a neural network, thus, almost linear with respect to the number of atoms in the material. Specifically, we have applied our method to a metal oxide structure interacting with a nucleic base guanine. We have focused on stoichiometric and O-defective anatase TiO2 (101) surfaces. The data set of the electronic density of states needed to train the neural network has been obtained by a DFTB+ numerical solver given an initial molecular geometry model, which computed a track of time-dependent geometry and their associated electronic density of states. We validated that the predicted electronic density of states deduced by our method and by DFTB tends to be very similar, thus, opening the door to other computations such that introducing our method in the process of generating the time-dependent geometry analysis.

Density of electronic states in silicon nanocrystals embedded in a SiO2 matrix and passivated by hydrogen

Subject of study. This study is devoted to the optical transitions and density of electron and hole states in silicon nanocrystals embedded in a SiO2 dielectric matrix and silicon nanocrystals passivated by hydrogen. Aim of study. The aim is to calculate the probability of optical transitions, density of electron and hole states, and absorption cross-section in silicon nanocrystals surrounded by different environments. Another goal is to adapt the tight-binding method for correct passivation of dangling bonds of silicon. Method. The calculations are performed using the variant of the tight-binding method that accounts for a large number of orbitals: s, p, d, and s∗. Main results. The local density of states of electrons and holes, probabilities of optical transitions, and absorption cross-sections of silicon nanocrystals passivated by hydrogen and nanocrystals embedded in a SiO2 matrix were calculated. It is shown that the electron and hole states in hydrogen-passivated silicon nanocrystals are localized within the crystal, and optical transitions occur at wavelengths in the range of 440–620 nm. The presence of the SiO2 matrix surrounding the nanocrystal increases the probability of optical transitions and leads to the appearance of the local density of states outside the nanocrystal, with radiative emission in the wavelength range of 410–620 nm. Practical significance. The results highlight the feasibility of utilizing silicon nanocrystals in photonics and photovoltaics. They are expected to contribute to the development of technology for creating silicon nanocrystals with specific optical properties.

Luminescence enhancement effects of CaxSr2‒xNb2O7:Er3+,Tm3+ phosphors for temperature sensing and anti-counterfeiting applications

Er3+- and Tm3+-doped CaxSr2‒xNb2O7 (CxS2‒xN, x = 0.6, 0.8, 1.0, 1.2, 1.4) phosphors with layered perovskite structure were designed. These phosphors exhibit a dominant emission peak at 549 nm under 980 nm laser excitation, attributed to the 4S3/2→4I15/2 transition. By increasing the content of Ca2+, the crystal field regulation of rare earth ions is realized and the luminescence enhancement is induced, which is manifested by the increase of 2H11/2,4S3/2→4I15/2 emission. Furthermore, the temperature sensing sensitivities of C0.6S1.4N:Er,Tm and C0.6S1.4N:Er,Tm based on non-thermally coupled energy levels were studied. Finally, an anti-counterfeiting imprint was prepared using phosphors, which have high brightness and excellent photothermal stability. This work not only confirms that closer ionic radii substitution enables to increase the electronic density of states, improve the crystal field symmetry and enhance the luminescence, but also provides a promising phosphor system for temperature sensing and anti-counterfeiting applications, opening up new prospects in the optimization of the optical properties of phosphors.

Velocity Map Imaging Photoelectron Spectroscopy of Silver Iodide Aerosol Particles.

The valence band electronic structure of isolated silver iodide nanoparticles (AgI NP) was investigated by vacuum-ultraviolet aerosol photoelectron spectroscopy using the velocity map imaging technique (VUV VMI-PES). The VUV VMI-PES results were obtained for polydisperse aerosol produced by aggregation of hydrocolloid of silver iodide particles 8-15 nm in size. The ionization energy of the AgI particles was found to be 6.0±0.1 eV with respect to the vacuum level. The DFT calculations showed that the main contribution to the density of AgI electronic states in the valence region originates from I 5p orbitals. The dependence of the asymmetry parameter on the electron energy showed that the value of the characteristic energy loss of excited photoelectrons was 2.7 eV, which coincided with the band gap of the nanomaterial.

Amorphous MoS2 from a machine learning inter-atomic potential.

Amorphous molybdenum disulfide has shown potential as a hydrogen evolution catalyst, but the origin of its high activity is unclear, as is its atomic structure. Here, we have developed a classical inter-atomic potential using the charge equilibration neural network method, and we have employed it to generate atomic models of amorphous MoS2 by melting and quenching processes. The amorphous phase contains an abundance of molybdenum and sulfur atoms in low coordination. Besides the 6-coordinated molybdenum typical of the crystalline phases, a substantial fraction displays coordinations 4 and 5. The amorphous phase is also characterized by the appearance of direct S-S bonds. Density functional theory shows that the amorphous phase is metallic, with a considerable contribution of the 4-coordinated molybdenum to the density of states at the Fermi level. S-S bonds are related to the reduction of sulfur, with the excess electrons spread over several molybdenum atoms. Moreover, S-S bond formation is associated with a distinctive broadening of the 3s states, which could be exploited for experimental characterization of the amorphous phases. The large variety of local environments and the high density of electronic states at the Fermi level may play a positive role in increasing the electrocatalytic activity of this compound.