First-principles Density Functional Theory Research Articles

Study on Pd-MoTe2 monolayer for adsorption and sensing of air decomposition products in air-insulated switchgear

Detecting characteristic decomposition components has become a popular method for assessing the operational stability of air-insulated switchgear. This paper investigates the adsorption and sensing properties of a Pd-modified MoTe2 (Pd-MoTe2) for two common defective gases, namely, NO2 and CO, in air-insulated switchgear and employs the first-principles density functional theory (DFT) to conduct the analysis. According to the findings, Pd has a preference for doping in the TMo site on the MoTe2 monolayer, with a binding energy (Eb) of −2.240 eV. The Pd-MoTe2 monolayer exhibits effective adsorption of NO2 and CO, with both molecules chemisorbed. The adsorption energies (Ead) for NO2 and CO are −1.307 eV and −1.550 eV, respectively. Furthermore, there is an evident reduction of the band gap for the Pd-MoTe2 upon adsorbing NO2, decreasing the resistance value. In short, the Pd-MoTe2 monolayer has shown great promise as a gas sensor, laying the groundwork for improving power system stability.

Theoretical prediction of two-dimensional CrSi2N4 as a potential anode material for Na-ion batteries

Efficient anode materials are critical for high-performance rechargeable lithium-ion batteries (LIBs) and sodium-ion batteries. This paper systematically investigates the potential of the CrSi2N4 monolayer as anode material for LIBs and sodium-ion batteries by first-principles density functional theory calculations. It was found that CrSi2N4 exhibits outstanding performance in sodium-ion batteries, with a low diffusion energy barrier of 0.10 eV and a high theoretical specific capacity of 490 mAh g−1. Meanwhile, the average open circuit voltage is 0.47 V, comparable to the typical anode materials. In addition, a small lattice constant change of 0.3%–3.1% ensures the cycling stability of CrSi2N4 in sodium-ion batteries. This work suggests a promising candidate anode material for sodium-ion batteries.

DFT insights into the adsorption mechanisms of lithium polysulfides on Ni2P (0001) surface for lithium–sulfur batteries

Reliable and sustainable energy storage systems are crucial for a renewable energy future. The ultrahigh theoretical specific capacity and energy density of lithium–sulfur batteries (LSBs) make them one of the most promising next-generation battery technologies. However, their large-scale applications are seriously limited by rapid capacity fading and poor Coulombic efficiency owing to the shuttling of lithium polysulfides (LiPSs). Herein, we investigate nickel phosphide (Ni2P) as an effective host material to realize high-performance LSBs based on first-principles density functional theory (DFT) calculations. Our calculated adsorption energies of the LiPSs species reveal that the Ni2P(0001) surface possesses moderate to high adsorption strength and the adsorption process is facilitated via charge transfer from the LiPSs to the interacting Ni2P(0001) surface atoms. Due to the strong interactions between Ni2P(0001) and LiPSs (Li2Sx, x = 1, 2, 4, 6 and 8), we observe elongation of the intramolecular Li–S bonds in LiPSs upon their adsorption. The stronger adsorption of Li2S coupled with its spontaneous dissociation suggests a faster charging process could occur on the on Ni2P(0001) surface. These results demonstrate that Ni2P can provide effective anchoring sites for the soluble LiPSs, potentially having implications for the design of electrodes for practical LSBs.

A first-principle study on the pressure-dependent structural, electronic, and optical properties of 4-Hydrazine Benzene Sulfonamide

This study utilizes first-principle density functional theory (DFT) to explore the high-pressure behavior of 4-hydrazine benzene sulfonamide. Our investigation, spanning pressures from 0 to 300[Formula: see text]GPa, delves into diverse properties of the crystal (C6H9N3O2S), encompassing the crystal structure, band gap, density of states, permittivity, and conductivity. Under increasing pressure, intriguing observations emerge. Distortions in the molecular structure manifest notably at 70, 130, and 270[Formula: see text]GPa, accompanied by distinctive anisotropic behavior in lattice constants. Notably, our scrutiny of the band gap and density of states exposes a transition from a semiconductor to a metallic state and back to a semiconductor state, illuminating the profound influence of pressure on the material’s electronic structure. At 0[Formula: see text]GPa, the real part of permittivity registers negative values within the 15.6–20.2[Formula: see text]eV energy range, suggesting the crystal’s inability to propagate light and its manifestation of metallic reflection properties. Conversely, at 270[Formula: see text]GPa, the imaginary part of permittivity indicates metallic characteristics within the electronic structure, alongside a substantial energy loss in the crystal’s real part of conductivity. Moreover, the imaginary part of conductivity unveils pronounced energy conversion between the driving electric field and current excitation, hinting at structural instability under this extreme pressure. This research contributes vital insights into the behavior of hydrocarbons under high pressure, filling crucial gaps in our understanding of their properties.

Surface band structure of the reconstructed Ir(001)-[formula omitted] surface

It is well known that the atomic structure of the Ir(001)-(5 × 1) surface consists of a quasi-hexagonal topmost layer on top of quadratic substrate layers. In the present work, we investigate how the electronic structure of Ir(001)-(1 × 1) is modified by the (5 × 1) reconstruction. For this purpose, we perform a first-principles density functional theory (DFT) calculation for semi-infinite Ir(001)-(1 × 1) and -(5 × 1) surfaces by employing the surface embedded Green’s function technique. It will be shown that surface bands on the (1 × 1) surface are strongly modified upon reconstruction. At the same time, we will demonstrate that one-dimensional (1D) surface bands localized in atomic rows in the [110] direction characterizing the buckled hexagonal layer emerge on the reconstructed surface.

Exploring sustainable corrosion inhibition of copper in saline environment: An examination of hydroquinazolinones via experimental and ab initio DFT simulations

Copper's potential in various applications is constrained due to environmental degradation, particularly in high-salinity environments, representing a sustainability concern. Herein, two novel hydroquinazolinones, namely 1-((4-hydroxynaphthalen-1-yl)methyl)-2-phenyl-2,3-dihydroquinazolin-4(1H)-one (DQ-H) and 1-((4-hydroxynaphthalen-1-yl)methyl)-2-(p-tolyl)-2,3-dihydroquinazolin-4(1H)-one (DQ-CH3), were analyzed for their ability to inhibit copper corrosion in a 3.5 % NaCl solution. The compounds, characterized by 1H and 13C NMR, were evaluated via potentiodynamic polarization curves, electrochemical impedance spectroscopy, and weight loss measurements. Comprehensive analyses utilizing scanning electron microscopy, Fourier Transform Infrared, and UV–vis spectroscopy have revealed insights into the surface morphology and the interactive nature of inhibitor molecules with the copper surface. Our findings highlight the formation of a strong, sustainable inhibitor film on the copper surface due to the addition of hydroquinazolinones, thereby exhibiting an enhanced polarization resistance and decreased double-layer capacitance. Both DQ-H and DQ-CH3 demonstrated a considerable inhibition effect, with efficiencies of 92 % and 94 % respectively, illustrating their potential for sustainable copper protection. Electrochemical impedance spectroscopy (EIS) results indicated a significant increase in polarization resistance from 605.7 (blank) to 9403 and 12861 Ω cm2, after the addition of DQ-H and DQ-CH3, respectively. Furthermore, the adsorption attributes of the compounds on the Cu(111) surface were examined using first-principles density functional theory simulation, revealing several covalent bonds formation. Our work aims to contribute to sustainability efforts in materials science by offering a corrosion-protective solution that is less harmful to the environment and more efficient in preserving copper's durability, particularly in saline environments.

Stability, electronic and optical properties of buckled XO (X = Ge, Cu) graphenylene monolayers: A first-principles study

The demand for sustainable semiconducting devices that can be used in various applications necessitates the development of revolutionary materials with multifunctional properties. Using van der Waals interactions corrected first-principles density functional theory (DFT) calculations, we propose porous g-XO (X = Ge, Cu) inorganic graphenylene monolayers. These monolayers extend the family of synthesized porous organic graphenylene materials. Stability checks reveal that the g-XO monolayers are energetically, mechanically, dynamically, and thermally stable. Additionally, g-GeO monolayer is auxetic 2D material. The auxetic property of g-GeO monolayer could be advantageous for important applications in mechanics and tissue engineering, electromechanical devices, and flexible electronics. Based on the HSE06 electronic band structure results, these g-CuO and g-GeO monolayers exhibit wide and ultra-wide indirect bandgap semiconducting properties, respectively. The satisfactory absorption coefficient of 104–105 cm−1 spanning the visible to UV region implies their potential for optoelectronics and UV shields applications. Our theoretical results provide a hints for the potential of these porous g-XO monolayers in energy harvesting/conversion, nanofiltration membranes, optoelectronic, thermoelectric, and flexible electronics.

Effect of uniaxial strain on the electronic and magnetic properties of N2SrRb: a DFT study

ABSTRACT Using the first-principles density functional theory calculations, we examined the effect of uniaxial strain on the electronic and magnetic properties of full-Heusler alloy N2SrRb. Our results show that N2SrRb is a ferromagnetic full-Heusler alloy, and it exhibits half metallic properties with 100% spin polarisation when no strain is applied. The half-metallic and magnetic properties of N2SrRb were retained under the ranges of tensile and compressive strain applied. The spin flip gap was found to increase as the tensile strain increases, while it decreases as the compressive strain increases. The mechanical properties show that the full-Heusler alloy is mechanically stable and having a ductile characteristics

Prediction of new 212 M2AB2 borides as a promising candidate for future engineering: DFT calculations

The elemental diversity is critical for identifying ternary MAB phases with exceptional properties by tuning bonding types and strength between constitutive atoms. The interactions between M and A atoms significantly impact the physical and chemical properties of MAB phases. M2AB2 (where M = Hf, Zr; A = Ga, Ge) was studied using first-principles density functional theory (DFT). Lattice constants (a, c) and internal coordinates have been found after optimization. The lattice parameters in terms of structure exhibit conformity with findings from earlier research. The electronic band structure (EBS) density of states (DOS) and density of states (DOS) have been determined. According to the band structures and density of states investigation, these compounds are electrical conductors. The elastic constants were computed using the stress-strain method. The computed elastic constants and phonon dispersion patterns support this newly found compound's mechanical and dynamical stability. The isotropic elastic moduli bulk modulus (B), shear modulus (G), Young's modulus (E), Poisson's ratio (v), and Vickers hardness (Hv) have been explored within the framework of the Voigte-Reusse-Hill approximation. Specific heat capacity, Debye temperature, entropy, Helmholtz free energy, and internal energy changes of M2AB2 (where M = Hf, Zr; A = Ga, Ge) compounds were investigated using thermodynamic characteristics. The minimum thermal conductivity (Kmin) and melting temperature (Tm) of the compounds have also been computed to assess whether they are suitable as thermal barrier coating (TBC) materials or for high-temperature applications. These compounds' optical properties have been studied, demonstrating their usefulness as coating materials for reducing solar heat absorption. The examined physical characteristics of M2AB2 (where M = Hf, Zr; A = Ga, Ge) are contrasted with those of comparable 212 and 211 MAB phases.

High Curie temperature and high magnetization potential Fe2CoS alloy soft magnet

Developing soft magnets is attracting extensive research efforts for several device applications and other issues. Here, we investigate the finite temperature magnetic properties of the Fe2CoS alloy using first-principles density functional theory calculations and Monte Carlo simulations. Without a demagnetization factor, it exhibits semi-hard-magnetic properties at room temperature. For instance, it exhibits a coercivity of 290 mT, a magnetic anisotropy constant of 218 kJ/m3, and a magnetic hardness parameter of 0.3. By considering the demagnetization factor at 300 K, the coercivity, magnetic anisotropy constant, and hardness parameter are reduced to 1.5 mT, 0.7 kJ/m3, and 0.035. Besides, compared to ferrites soft magnets, the Fe2CoS alloy shows a high relative permeability of 10,000 and low energy loss of 0.16 Watt/kg. The curie temperature (940 K) and high saturation magnetization MS (1.49 T) of the Fe2CoS alloy are significantly higher than those of soft ferrites and Permalloy. Therefore, we propose that the Fe2CoS alloy can be used as a potential Fe-based soft magnet.

In-Plane Hybrid Structure of h-BN and Graphene for Hydrogen Storage Application: A First-Principles Density Functional Theory Study

In-Plane Hybrid Structure of h-BN and Graphene for Hydrogen Storage Application: A First-Principles Density Functional Theory Study

First-principles prediction of n-type diamond: novel co-doped structure using N and Be impurities

To address the limitation of diamond-based electronic devices, a comprehensive study on n-type diamond is crucial. A novel dopant structure, nitrogen–beryllium co-doping, is proposed for achieving n-type doping. The dopant structure, electronic property, synthesis route and internal strain are analyzed using first-principles density functional theory. The formation energy and ionization energy of xN–Be (x = 1–4) are compared to elucidate the distinct doping effects associated with varying numbers of N atoms. The formation energy initially decreases and then gradually increases with an incensing number of N atoms. Notably, 3N–Be and 4N–Be exhibit appealing n-type diamond properties, with low ionization energies of 0.30–0.41 eV (3N–Be) and 0.23–0.37 eV (4N–Be). To facilitate the preparation of 3/4N–Be co-doped diamond, a non-molecular synthetic route is proposed, involving the prior generation of the 3N-V and 4N-V. The 3/4N–Be co-doped diamond exhibits relatively small strain energy. Finally, this investigation highlights the potential of 3/4N–Be co-doping as excellent choices for n-type dopants, providing a greater variety of n-type structures with similar ionization energy compared to 4N–Li co-doping.

Elastic Properties of Alloyed Cementite M3X (M = Fe, Cr; X = C, B) Phases from First-Principle Calculations and CALPHAD Model.

Fe-Cr-C-B wear-resistant steels are widely used as wear-resistant alloys in harsh environments. The M3X (M = Fe, Cr; X = C, B) cementite-type material is a commonly used strengthening phase in these alloys. This study investigated the mechanical properties of cementite (Fe, Cr)3(C, B) using the first-principle density functional theory. We constructed crystal structures of (Fe, Cr)3(C, B) with different concentrations of Cr and B. The bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and hardness of the material were calculated, and a comprehensive mechanical property database based on CALPHAD modeling of the full composition was established. The optimal concentrations of the (Fe, Cr)3(C, B) phase were systematically evaluated across its entire composition range. The material exhibited the highest hardness, shear modulus, and Young's modulus at Cr and B concentrations in the range of 70-95 at% and 40 at%, respectively, rendering it difficult to compress and relatively poor in machinability. When the B content exceeded 90 at%, and the Cr content was zero, the shear modulus and hardness were low, resulting in poor resistance to deformation, reduced stiffness, and ease of plastic processing. This study provides an effective alloying strategy for balancing the brittleness and toughness of (Fe, Cr)3(C, B) phases.

First-principles study of intrinsic defects and helium in tungsten trioxide

Understanding the behavior of intrinsic defects and helium (He) in tungsten oxides is useful for the application of tungsten (W) in a fusion environment because of the oxidation of W surfaces. The formation and diffusion energies of intrinsic defects and He in monoclinic γ-WO3 have been investigated using first-principles density functional theory calculations. The formation energy and diffusion activation energy of O defects are lower than W defects. O vacancy prefers to diffuse along the ⟨001⟩ direction, then followed by ⟨010⟩ and ⟨100⟩ directions; however, the W vacancy is immobile at temperatures lower than 2000 K. The stability of Schottky defects (SDs) is sensitive to their geometry and orientation. W interstitials prefer to move along the [100] direction, while O interstitials jump around W atoms rather than through the W quasi-cubic centers. He interstitial atoms are predicted to have a high solubility and an anisotropic diffusion mechanism in γ-WO3. In addition, the effect of biaxial strain on the solubility and diffusivity of He interstitials was investigated. He interstitials prefer to reside at individual sites rather than clusters. He atoms are weakly trapped by single vacancies or SDs. Vacancies assist the local migration of nearby He. Correspondingly, He self-clustering and bubble formation are less likely to form in γ-WO3 relative to bcc W. The energetics obtained in this work can be used to predict the microstructure evolution of the WO3 layer on a W substrate exposed to He plasmas at different temperatures.

First-principles study of LiFePO4 modified by graphene and defective graphene oxide

The energy stability and electronic structural of graphene and defective graphene oxide (GO) parallel to the surface of LiFePO4 (010) were theoretically investigated by using first-principles density functional theory calculations within the DFT + U framework. The calculated formation energy shows that GO coating on the surface of LiFePO4 (010) is energetically favorable and has higher bond strength compared to graphene. The calculation of the electronic structure indicates that the emergence of band in-gap states originates from graphene coating, with adsorbed O atoms contributing significantly above the Fermi level. Electron density difference indicate that GO stands on the LFP (010) surface through C–O and Fe–O bonds, rather than relying on van der Waals forces placed parallel to the LFP crystal, with the chemical bond at the LFP/GO interface (Fe–O–C) both anchoring the coated carbon layer and promoting electron conductivity at the interface. In addition, LFP/GO shows superior electrochemical performance, Atomic Populations suggests that the average Fe–O bonding on the surface of LiFePO4 (010) was clearly changed after graphene or GO coating, which led to the expansion of Li+ channels and favored the migration insertion and extraction of Li+.

Unleashing the power of Fe2(MoO4)3 as a multifunctional material for energy storage and photocatalysis with theoretical insight from density functional theory

In a world facing urgent environmental issues and an increasing demand for sustainable energy solutions, the quest for versatile materials that can tackle a wide range of energy challenges has become essential. This paper aims to capture the diverse capabilities of Fe2(MoO4)3, highlighting its role as a multifunctional material applicable in both photocatalysis and energy storage. A simple strategy for the synthesis of Fe2(MoO4)3 via a one-step hydrothermal route is designed to allow for multifunctional properties, such as high photocatalytic activity under visible light irradiation and excellent electrochemical behaviour for its use as the electrode in a supercapacitor.The photodegradation tests reveal that Fe2(MoO4)3 can efficiently degrade 96 % of methylene blue (MB) dye within only 70 min of exposure to visible light. The maximum Langmuir adsorption capacity of Fe2(MoO4)3 was 94.33 mg/g at 30 °C and it also followed pseudo-second order kinetic models as well. The result of thermodynamic data showed that the adsorption was spontaneous and endothermic in nature. At the same time the use of Fe2(MoO4)3 as an electrode material for supercapacitors exhibits impressive characteristics, including a high specific capacitance (472 F/g at 1 A/g), excellent cycling stability (85.4 % retention after 10,000 cycles), impressive rate capability (323 F/g even at 6 A/g), as well as noteworthy energy and power density (16 Wh/kg and 1497 W/kg). The capacitive and diffusion-controlled contribution is also investigated for Fe2(MoO4)3 using Dunn's method. First-principles Density Functional Theory simulations also support our experimental findings by demonstrating that maximum quantum capacitance can reach 580 F/g at an electrode potential of 0.65 V. All of these promising results demonstrate the multifunctionality of Fe2(MoO4)3 as a potential electrode material as well as a novel photocatalytic candidate for organic contaminant removal in water.

Raman spectroscopy of zirconium hydride

The characterization of zirconium hydride is important in the nuclear industry because of the hydrogen-induced embrittlement of Zircaloy cladding and its use as a neutron moderator. This paper introduces the use of Raman spectroscopy for the characterization of zirconium hydride. First-principles density functional theory (DFT) calculations were used to predict the Raman spectra of ζ-ZrH0.5, γ-ZrH, δ-ZrH1.5, δ-ZrH1.66, and ε-ZrH2 with all their predicted symmetries; ζ-ZrH0.5 (P3m1, R3¯m, C2/m, Cm, Cmmm, and Pn3¯m); γ-ZrH (P222, Ccce, and P42/mmc); δ-ZrH1.5 (P4¯m2, P42/mcm, Fmmm, Pn3¯m, Ibam, P2/c, PI, and P42/nnm); δ-ZrH1.66 (Fm3¯m); and ε-ZrH2 (Fm3¯m, R3¯m, and I4/mmm). Two samples of Zircaloy-4 containing 133 wt ppm and 360 wt ppm hydrogen were characterized by Raman spectroscopy, showing two signal lines at 215 cm−1 and 1,187 cm−1, which were assigned to the presence of δ-ZrH1.66. These signals had a good spatial correlation with visible hydride precipitates in Raman spectroscopy images. This work provides the basis for the characterization of all possible zirconium hydride compositions and structures using Raman spectroscopy.

First-principles density functional theory for the structural, electronic, and phonon calculations of Ca-doped bilayer graphene

Density functional theory is adopted for the electronic structure and phonon calculation of Ca-doped bilayer graphene. The AA and AB stacking configurations are simulated, and the atoms are relaxed so that the atomic forces working on them are close to zero ([Formula: see text] eV/Å). In the final relaxation, the symmetry of [Formula: see text] is [Formula: see text] for AA stacking and [Formula: see text] for AB stacking. The formation energy of AA stacking (1.72 eV) is much lower than that of AB stacking ([Formula: see text] eV). According to the electronic structure calculations, the Dirac point shifts down from the Fermi level, indicating that the Ca atom behaves as an n-type dopant. The calculated Fermi velocities for pristine bilayer graphene are [Formula: see text] (AA stacking) and [Formula: see text] m/s (AB stacking). Those for Ca-doped bilayer graphene are [Formula: see text] (AA stacking) and [Formula: see text] m/s (AB stacking). Phonon calculations revealed that considering the vibrational effect, the defect concentration is [Formula: see text] cm[Formula: see text] in the AA stacking system. Meanwhile, concentration is deficient in the AB stacking system due to the asymmetric defect configuration.

Mn-L-based multifunctional molecular spintronic device: A first-principles investigation

A transition metal coordination complex Mn-L-based multifunctional molecular spintronic device is proposed and its spin-polarized transport properties in two magnetic configurations (parallel and anti-parallel alignments) are evaluated using the first-principles density functional theory and non-equilibrium Green’s function method. Four high-performance physical effects, including spin-filtering, spin-rectifying, giant magnetoresistance and negative differential resistance, are revealed in the proposed device. The physical mechanisms are analyzed through the spin-resolved bias-dependent transmission spectra, and projected device density of states spectra. These results demonstrate that the proposed system holds great promise in developing the multifunctional molecular spintronic devices.

Influence of water on the thermoelastic properties of Fe bearing ringwoodite: A first-principles study

Using first-principles density functional theory (DFT), we model the thermoelastic properties of hydrated ringwoodite (γ-(Fe, Mg)2SiO4), a potential water reservoir in the Earth's mantle transition zone (MTZ). Our calculations indicate that hydration, in general, leads to a reduction in the sound wave velocity of ringwoodite. However, increased pressure tends to suppress this reduction. For our 1.56 wt% H2O containing ringwoodite model, we find that the suppression is so large that at pressure and temperature (P-T) conditions relevant to the lower part of the MTZ the sound wave velocities for the hydrous (1.56 wt% H2O) ringwoodite become very similar to that of the anhydrous ringwoodite. However, when the water concentration is increased to 3.3 wt%, the pressure-induced suppression of the velocity reduction due to hydration is not so significant. We have given a plausible explanation for the same on the basis of the electronic structure of the hydrous ringwoodite models. We conclude that in the lower part of the MTZ, seismic wave data is sufficiently robust to detect regions of very high-water content (∼3.3 wt%). However, if the water concentration is less than 1.56 wt%, sound wave velocities may not be able to precisely detect the state of hydration of the MTZ.