First-principles Investigation Research Articles

First-principle investigation the initial oxidation of methane on Pd doped LaCo0.2Fe0.8O3-δ anode surfaces of solid oxide fuel cells

Initial oxidation of methane (CH4) is essential for subsequent oxidation reactions on anode surfaces of solid oxide fuel cells (SOFCs). Here first principle method was employed to investigate the initial oxidation mechanism of CH4 on Pd doped LaCo0.2Fe0.8O3-δ (LCF) anode. Results show that Pd-doping decreases formation energies of surface oxygen vacancy. The adsorption ability of CH4 molecules is also improved on perfect LCF surface by Pd-doping. Dissociation barriers of CH4 on LCF surfaces are greatly decreased with min value of 1.14 eV by Pd-doping and surface oxygen vacancy compared to those on perfect and defective LCF surfaces (min values of 1.76 and 1.34 eV, respectively). Results of Bader charges and bond lengths of CH4 (or CH3) and OH show that the initial oxidation of CH4 molecules is namely the oxidation of dissociated H atoms from CH4 molecules. And higher valences of surface metal atoms interacted with CH4 molecules mean the lower dissociation barriers of CH4 molecules.

First-principles investigation of the thermal properties of XO (X=Be, Mg and Sr) nanosheet

The electronic structures and thermal properties of hexagonal XO ([Formula: see text], Mg and Sr) nanosheets are studied within the density functional theory. The thermal properties are computed using the specified structural parameters of the electronic properties. Thermal properties including entropy, enthalpy, free energy and heat capacity for XO nanosheets are reported. It is found that BeO is an insulator, whereas MgO and SrO are semiconductors based on the energy gap value within GGA and HSE06. The electronegativity and bonding nature of XO nanosheets differ, resulting in considerable variations in thermodynamic parameters that follow a similar pattern as a function of temperature. Enthalpy and entropy increase with temperature whereas free energy falls, owing to a change in the binary oxide internal energy of the system and the electron density distribution. Thermal energy absorbed by the lattices grows with increasing temperature to the point at which all of their modes are activated and the systems start to display unharmonicity deviating from a linear dependence. Variable parameter ranges for XO nanosheets are useful in the development of thermoelectric nanodevices.

New stable inorganic BX (X= P, As, Sb) biphenylene and graphenylene monolayers: A first-principles investigation

Porous two-dimensional (2D) materials with semiconducting property are promising candidates for a variety of multifunctional energy harvesting applications. Motivated by the successful synthesis of porous organic biphenylene and graphenylene materials, herein, we demonstrate the ground-state properties of a new family of b-BX and g-BX monolayers inorganic biphenylene and graphenylene monolayers using first-principles calculations based on density functional theory. Stability tests show that the b-BX and g-BX monolayers are energetically, mechanically, dynamically, and thermally stable. Moreover, g-BX (X = As, Sb) monolayers are auxetic 2D materials. According to the HSE06 electronic band structure results, these monolayers of b-BX and g-BX exhibit moderate and wide indirect bandgap semiconducting properties. These novel ground state properties of b-BX and g-BX monolayers demonstrate their aforementioned potential applications in addition to optoelectronic, thermoelectric, and flexible electronics. Besides all these newly proposed b-BX and g-BX monolayers expand the family of inorganic biphenylene and graphenylene non-magnetic materials.

SiX2 (X = S, Se) Nanowire Gate-All-Around MOSFETs for Sub-5 nm Applications.

The gate-all-around (GAA) field-effect transistor (FET) holds great potential to support next-generation integrated circuits. Nanowires such as carbon nanotubes (CNTs) are one important category of channel materials in GAA FETs. Based on first-principles investigations, we propose that SiX2 (X = S, Se) nanowires are promising channel materials that can significantly elevate the performance of GAA FETs. The sub-5 nm SiX2 (X = S, Se) nanowire GAA FETs exhibit excellent ballistic transport properties that meet the requirements of the 2013 International Technology Roadmap for Semiconductors (ITRS). Compared to CNTs, they are also advantageous or at least comparable in terms of gate controllability, device dimensions, etc. Importantly, SiSe2 GAA FETs show superb gate controllability due to the ultralow minimum subthreshold swing (SSmin) that breaks "Boltzmann's tyranny". Moreover, the energy-delay product (EDP) of SiX2 GAA FETs is significantly lower than that of the CNT FETs. These features make SiX2 nanowires ideal channel material in the sub-5 nm GAA FET devices.

From Stability to Superconductivity: A First-Principles Investigation of Sr–N Phases under Pressures and the N-Enhanced Tc Phenomenon

From Stability to Superconductivity: A First-Principles Investigation of Sr–N Phases under Pressures and the N-Enhanced <i>T</i>_c Phenomenon

The Bell-Evans-Polanyi relation for hydrogen evolution reaction from first-principles

The versatile Bell-Evans-Polanyi (BEP) relation stipulates the kinetics of a reaction in terms of thermodynamics. Herein, we establish the BEP relation for the hydrogen evolution reaction (HER) from fundamental electrochemical principles leveraging the Butler-Volmer relation for a one-step, one-electron process and the transition state theory. Based on first-principles investigations of HER mechanisms on fourteen metal electrodes, we firmly justify the BEP relation solely using an easy-to compute hydrogen adsorption free energy and universal electrochemical constants.

First-principles Investigations of Structural, Thermodynamic, Optoelectronic and Thermoelectric Properties of Rb2CuMF6 (M = As3+, Bi3+) Eco-friendly Halide Double Perovskites: Materials for Green Energy Applications

First-principles Investigations of Structural, Thermodynamic, Optoelectronic and Thermoelectric Properties of Rb2CuMF6 (M = As3+, Bi3+) Eco-friendly Halide Double Perovskites: Materials for Green Energy Applications

Pressure influenced electronic phase transition, mechanical, optoelectronic, and transport characteristics of double perovskite Rb2AgSbCl6: A first-principles investigation

In this work, we used density functional theory (DFT) simulations to investigate the structural, elastic, electronic, optical, and transport characteristics of pressure-induced Rb2AgSbCl6. By calculating the octahedral and the tolerance factors, the phase stability has been verified. The calculated formation energy and Gibbs free energy values have demonstrated the thermodynamic stability of the material. The outcomes of the mechanical behavior analysis revealed that the pressure-driven Rb2AgSbCl6 is mechanically stable and sustains ductility as well as anisotropy. Additionally, as the pressure is increased from 0 GPa to 100 GPa, the band gap has been reduced from 2.64 eV to 0 eV. The hydrostatic pressure of 100 GPa was the critical pressure at which the material revealed a metallic nature. The optical properties such as absorbance and optical conductivity shift towards lower energy and comparatively higher at increased pressure with minimal energy loss. The thermoelectric characteristics are examined utilizing the BoltzTraP code at different pressures. The figure of merit (ZT) value was increased from 0.76 to 0.80 with the increase in pressure at room temperature. These characteristics render pressure-influenced Rb2AgSbCl6 favorable candidates for utilization in solar cells as well as thermoelectric devices.

First-principles investigation on potential profile induced in graphene by surface and edge metal contacts

To utilize graphene as an electronic device graphene has to be brought into contact with a metal electrode and the metal contact has a significant impact on the characteristics of the device. We have investigated the potential profile induced in graphene layer by metal contacts, which describes how charges are redistributed between metal and graphene in order to eliminate the difference in work function between them, by using first-principles calculations. It is found that the potential profiles are much different between surface and edge contact metal/graphene junctions. For surface contacts the potential profile is significantly influenced by Pauli exclusion interactions and bond formation between metal and graphene. On the other hand, the edge contacts lack Pauli exclusion interactions and the non-graphene-like metallic states of C atoms near the metal edges, which are induced by bond formation, are suggested to have a major effect on eliminating the work function difference.

The unique geometries and magnetic anisotropy energy of FenPt (n = 3–13) clusters: A first-principles investigation

Enthusiasm for exploring magnetic anisotropy energy (MAE) and spin–orbit coupling (SOC) effects in magnetic studies of transition metal alloy clusters remains high. In this paper, the first-principle method was used to investigate the global minimum energy structure of FenPt (n = 3–13) clusters and their interesting magnetic properties. Comparative structural analyses show that FenPt (n = 3–13) clusters have unique structures, and their relative stability analyses indicate that the increase in the number of atoms influences the geometrical arrangement of the clusters. The exploration of magnetic properties has focused on two areas. First, FenPt (n = 3–13) is found to have a large magnetic moment, while the magnetic moment increment surprisingly varies in the same way in different cases with and without the inclusion of SOC effects. Second, the calculations show that FenPt (n = 3, 4, 9, 13) has MAE, ranging from 1.420-2.687 meV/atom. The SOC matrix results show the interaction of Pt dx2-y2 and Pt dxy, and the interaction of Pt dz2 and Pt dyz, exhibit an indispensable force in determining the MAE.

Effect of solutes segregation in a binary TiAl alloy: A first-principles calculation method

Comprehending the interfacial structures and energetics of interfaces between γ-TiAl and α2-Ti3Al phase is critical to understanding the stabilities of the binary-phase TiAl-Ti3Al alloy. Here a comprehensive first-principles investigation is reported on the structures and energetic properties of γ-TiAl(111)/α2-Ti3Al(0001) interfaces with 19 segregated transition metals considered. The results indicate that all considered atoms have a tendency to segregate at the interface. The interfacial strength enhancement occurs after V, Cr, Mn, Fe, Nb, Mo, Tc, Ru segregated in TiAl, Ag segregated in Ti3Al, and almost all solute atoms can improve interface stability. Compared with the pure interface, the bonding between the segregated atoms and the surrounding atoms is stronger at the interface after V or Nb segregation, while the bonding between Cd and the surrounding atoms is weaker. Our calculations provide the necessary interfacial structures and energetics for predicting the stabilities of binary TiAl alloy.

First-principles investigations for electronic and thermoelectric properties of XGeF[formula omitted](X = K, Rb): Nonlocal corrections and SCAN insights

In this research work we have studied the electronic band structures, density of states and thermoelectric parameters of fluorine based cubic perovskites KGeF3 and RbGeF3 using PW, PBE, SCAN, rVV10 and vdW-DF3 exchange correlation functionals implemented in Quantum ESPRESSO for thermoelectric applications. The lattice constant and bulk modulus of KGeF3 (RbGeF3) is 4.409 (4.407 Å) and 50.8 (51.8 GPa), respectively. KGeF3 has band gap of 1.917eV and RbGeF3 has band gap of 1.982eV with PBE. The band structures of both compounds are consistent to total density of states. The Seebeck coefficient, power factor, electrical and thermal conductivity are studied in a wide range of temperature from 0 to 800K. The detailed study of band gaps and thermoelectric parameters with variety of DFT methods indicates the significance of KGeF3 and RbGeF3 in thermoelectric devices under high temperature.

First-principles investigation of Cu/Ti-TM/Si (TM=W, Ru) interfaces: Role of Ti-TM binary alloys as diffusion barrier layers

This study employs first-principles calculations to investigate the role of Ti-TM (TM=W, Ru) binary alloys as diffusion barrier layers in Cu/Ti-TM/Si interfaces, which are critical for enhancing the performance and reliability of microelectronic devices. The calculated results reveal that TiRu and Ti4W12 alloys exhibit exceptional stability and low contact resistance, outperforming traditional Cu/Si interfaces. The introduction of these alloys into the interface structure results in a reduced Cu s-d coupling effect, which is pivotal for inhibiting Cu diffusion. Additionally, the presence of pseudogap features and enhanced electron distribution at the interface indicate strong atomic interactions, contributing to the formation of covalent bonds and further improving barrier properties. The findings suggest that TiRu and Ti4W12 alloys are promising candidates for diffusion barrier layers, offering a balance of low contact resistance, thermal stability, and effective Cu diffusion inhibition. Therefore, from the results, it is concluded that the formation of the new interface structure will improve performance in various aspects, and thus the strategy can be applied in various directions, such as new energy materials, electronic materials, and so on. In addition, the combination of the previous work and the present work suggests that Ti-based alloys have the potential to be used as diffusion barrier materials.

First-principles investigations and MOCVD growth of Si-doped β-Ga2O3 thin films on sapphire substrates for enhancing Schottky barrier diode characteristics

In the realm of high-power electronics, the potential of gallium oxide (β-Ga2O3) as a front-runner material has garnered significant attention due to its wide bandgap and the capacity to withstand high critical electric fields. To push the boundaries of performance for β-Ga2O3 devices, a meticulous exploration into the effects of silicon (Si) doping on β-Ga2O3 films was carried out using the metalorganic chemical vapor deposition (MOCVD) technique with various tetraethoxysilane (TEOS) flow rates (0–30 sccm). The Si-doped β-Ga2O3 films were systematically studied and characterized using XRD, SEM, and XPS techniques. XRD patterns demonstrated the preservation of the β-Ga2O3 monoclinic structure in the Si-doped β-Ga2O3 films, without any evidence of secondary phases. In addition to this, first-principles calculations were performed to explore the incorporation of Si atoms in Ga2O3 supercells, which revealed the preference of Si atoms to occupy substitutional Ga tetrahedral sites within the Ga2O3 lattice. Through the utilization of Si-doped β-Ga2O3 films, a unique design of donut-shaped Schottky barrier diode (SBD) was successfully engineered. Remarkably, the Si-doped β-Ga2O3 SBD (employed with 20 sccm TEOS flow rate) exhibited the breakdown voltage (Vbr) of 497 V and Baliga's Figure of Merit (BFOM) value of 1.16 kW/cm2, which is five-order higher BFOM compared to undoped β-Ga2O3 SBD. This substantial improvement in BFOM underscores the significant potential of Si-doped β-Ga2O3 films for high-power electronics, opening avenues for enhanced device efficiency and capabilities.

A First-Principles Investigation of InSiN2 Monolayer: A Novel Two-Dimensional Material with Enhanced Stability and Tunable Vibrational and Electronic Properties

A First-Principles Investigation of InSiN₂ Monolayer: A Novel Two-Dimensional Material with Enhanced Stability and Tunable Vibrational and Electronic Properties

A first-principles investigation of light weight high mechanical performance high-entropy carbides: The research of bottom-up compositional designing

Designing high-entropy carbides with light weight and high mechanical performance is a promising strategy for upgrading titanium carbides applied in fields of aerospace materials. Herein, a bottom-up compositional designing method and the density functional theory calculations are combined, and properties of the six high-entropy carbides are investigated developed from the light-weight (Ti1/3Zr1/3V1/3)C medium-entropy carbide. The five of them are predicted to be preparable except for (W0·25Ti0·25Zr0·25V0.25)C. Among them, (Nb0·25Ti0·25Zr0·25V0.25)C exhibits the both low density and excellent mechanical performance: for density 5.471g/cm3, Young's modulus 456.4GPa, Vicker's hardness 23.76GPa, fractural toughness 3.371MPa∙m1/2, low-temperature and high-temperature friction resistance indicators 0.052 and 0.064GPa, and melting point 3974±300K. The ab-initio simulations also reveal its good high-temperature strength and toughness, showing the predictable potential for upgrading traditional titanium carbide based materials.

Influence of high pressure on mechanical and electronic properties of C3060 allotropes—A first-principles investigation

The influence of external uniaxial pressure, ranging from 0 GPa to 50 GPa, on (3,0)(6,0) carbon (C3060), is examined through first-principles calculation. The mechanical descriptors, including elastic constants, bulk modulus, shear modulus, and Young's modulus, are studied and reported. Moreover, these characteristics demonstrate the adaptable robustness of C3060 to mechanical stress under various pressure conditions. Also, the ductility and brittleness analysis is obtained based on Cauchy pressure, Poisson's ratio, and Pugh's criteria. The structural and dynamical stability of C3060 are ensured using cohesive formation energy, phonon band spectrum, and phonon density of states. Further, the thermodynamic properties of C3060 under high pressure are discussed with regard to Gibbs free energy and entropy. Also, the electronic properties of C3060 under pressure within the range of 0 GPa–50 GPa are explored based on the band structure and projected density of the state spectrum. In short, this work emphasizes how uniaxial pressure influences the mechanical characteristics and electronic attributes of C3060, providing information on the adaptability of the material's structural features with regard to mechanical attributes.

Microwave assisted synthesis of nickel oxide nanoparticles at different pH via sol gel method: Experimental and first-principles investigations

Nickel oxide (NiO) nanoparticles were synthesized at different pH levels via a sol–gel method and calcined using microwave assistance. The study explored the effects of pH on NiO nanoparticles morphology, structure and electronic properties. Density functional theory (DFT + U) calculations were employed to investigate the structural and electronic properties of the material. NiO synthesized at pH 8 displayed superior crystallinity and particle size distribution, with spherical-like nanoparticles averaging 3 nm in size. DFT + U calculations revealed a band gap of 4.07 eV and a surface energy convergence of 51 meV/Å2, indicating stability. These findings suggest pH 8 as the optimal condition for NiO synthesis. Electrochemical tests demonstrated a high specific capacitance of 87.7F g−1 at a scan rate of 10 mV s−1, indicating promising electrochemical properties for supercapacitor applications.

Spheroidization of Sulfide in Sulfur Bearing Steels by Oxygen: An Experimental and First-Principle Investigation

Spheroidization of Sulfide in Sulfur Bearing Steels by Oxygen: An Experimental and First-Principle Investigation

First-principles investigation of elastic anisotropy and thermal transport property of transition metal monosilicides CrSi, TiSi, and ZrSi under pressure

In this paper, the influence of pressure on the elastic anisotropy and thermodynamics of CrSi, TiSi, and ZrSi monosilicides are investigated by the first-principles method. Those three alloys have elastic anisotropy, and the degree of anisotropy meets the relationships TiSi > ZrSi > CrSi. In addition, all the elastic anisotropy is enhanced with the increasing pressures. The melting point and Vicker’s hardness are investigated, and the results show that CrSi, TiSi, and ZrSi alloys may be promising high-temperature and hard materials. Furthermore, the lattice thermal conductivity is calculated by Slack’s equation only using the elastic properties. The pressure-dependent Debye temperature, Grüneisen parameter, and lattice thermal conductivity are systematically analyzed. Debye temperature enhances with increasing pressure while the Grüneisen parameter reduces with pressure. Consequently, the lattice thermal conductivity can be enhanced by the pressure, which benefits heat transportation. The calculation reveals that the pressure can effectively control the elastic anisotropy, Deby temperature, Grüneisen parameter, and the lattice thermal conductivity, which is useful for its practical application in industry.