First-principles Investigation Research Articles

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-LDA, PBE-GGA, 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 investigations on the physical properties of the double perovskite Cs2OsI6

The double perovskites, as a novel material with promising applications in solar cells, have garnered significant research interest. The mechanical, electrical, optical, and thermodynamic characteristics of Cs2OsI6 are systematically studied using first-principles calculations. The material's mechanical stability satisfies the Born criteria, and it exhibits commendable elasticity and anisotropy. The application of the HSE06 hybrid functional reveals that Cs2OsI6 has a direct band gap of 1.14 eV at the Γ-point, with electronic states primarily originating from the I-p orbitals and Os-d orbitals. The optical properties, including the dielectric function, refractive index, and absorption coefficient, indicate that it has a strong UV absorption capacity. The thermodynamic properties, including the Debye temperature, heat capacity, enthalpy, entropy, and free energy, conform to the laws of thermodynamics. The results indicate that Cs2OsI6 exhibits good stability with changes in temperature. In addition, it has a suitable band gap and a strong light absorption coefficient, making it suitable for photovoltaic applications. It has great potential to be a candidate for perovskite solar cell materials.

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-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.

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

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.

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.

First-principle investigation of lead-free double perovskites Cs2MScCl6 (M = Na, K) for optoelectronic and thermoelectric applications

Double perovskite optoelectronic devices are gaining popularity due to their advantageous features, such as an efficient and easy-to-manage crystalline structure. In this study, we looked into the optoelectronic, mechanical, and thermoelectric attributes of Cs2MScCl6 (with M being Na or K) using density functional theory. The obtained results show that both compounds can exist stably in cubic double perovskite structure, space group Fm3¯m . The electronic band structures of Cs2NaScCl6 and Cs2KScCl6 demonstrate a direct semiconducting band gap of 3.829 eV and 3.996 eV, respectively. As the pressure rises up to 200 GPa, Cs2KScCl6 reveals extraordinary tunability along with an indirect band gap of 2.000 eV. Moreover, optical analysis—comprising dielectric constant calculations, absorption coefficient measurements, refractive indices checks, reflectivity assessments, energy loss estimations, and electrical conductivity appraisals—shows promising results too. Specifically, the absorption coefficient and conductivity predominantly fall within the ultraviolet range under normal atmospheric pressure. The thermoelectric characteristics suggest a noteworthy Seebeck coefficient, low thermal conductance and good figure of merit implying it could be used in the domain of sustainable energy.

High-performance supercapacitor electrodes: Hierarchical integration of bimetallic structures incorporating silver and copper phosphates with a 3D fernlike stellar dendritic architecture

Batteries and supercapacitors remain at the front of research within the field of energy storage technologies. Over the years, the continues evolution of battery and supercapacitor device components has demonstrated remarkable advancement, evolving from simple metal blocks to complex, porous, and engineered structures composed of metal-based active materials. Towards this goal, transition metal phosphates (TM-POs) offer significant role enhancing the properties and architecture of the resulting metal-based active materials. This study introduces a unique electrode material with a dendritic structure of silver copper phosphates, derived from AgPO3 integrated with hexagonal Cu2P2O7. The improved electrochemical performance of silver copper phosphates compared to pristine AgPO3 and Cu2P2O7 is demonstrated by its increased specific capacity, reduced resistivity, higher redox activity, and a more advantageous diffusion-dominated storage mechanism. An assembled solid-state symmetric (SSCs) device, using silver copper phosphate electrodes exhibits a capacitance of 298.5 F g−1 at 15 mA cm−2, and high energy density of 20.3 Wh kg−1 with superior power density, also retains 91.7 % of its capacitance after 7000 cycles. When assembled a solid-state asymmetric supercapacitor (SSACs), as an integrated device using activated carbon and silver copper phosphate electrodes exhibits a high energy density of 30.62 Wh kg−1 at a power density of 1334 W kg−1 with retaining its capacity retention of 87.9 % even after 10,000 cycles. The enhanced capacity performance is further evaluated through first-principle investigations, elucidating that the distinct and intact heterostructure of silver copper phosphate exhibits improved metallic characteristics. This research of innovative electrodes holding superior properties holds potential for advancing next-generation electrodes for supercapacitor devices.

First-principles investigation of the interaction between oxygen and alloy atoms in [formula omitted]-zirconium

Zirconium alloys, being crucial materials in the nuclear industry, frequently encounter issues related to oxidative corrosion. Understanding the interaction between O atom and alloying atoms at the atomistic scale is helpful for optimizing Zr alloys with improved corrosion resistance. In the present study, a first-principles approach is used to understand the stability and diffusion properties of an O atom in α-Zr with different alloy atoms (Sn, Nb, Fe and Cr). Our findings reveal that the most stable position for oxygen is always the octahedral (Oct) site whether it coordinates with an alloy atom or not. Comparing to other alloy atoms, Fe tends to exclude interstitial O even at the long range and the interaction is stronger than others, while the long-range interaction of Nb is the weakest. All alloy atoms considered in this work can enhance interstitial O diffusion rate, and promote the anisotropy of O diffusion. This work also confirms that the kinetically resolved activation method is a reliable method to predict the O diffusion barrier in α-Zr.

First-principles investigation on adsorption poisoning and heterogeneous nucleation mechanisms in Ca modified primary Mg2Si phase

We employed first-principles calculations to investigate the adsorption poisoning and heteroepitaxial nucleation mechanisms in the Ca modification of the primary Mg2Si phase. The extensive computations considering various factors such as lattice mismatch, interface energy, adsorption energy, charge density, work of adhesion, and interface mechanical properties, as well as comparisons of interface stacking modes reveal that Ca modification of the primary Mg2Si phase can occur through both adsorption poisoning and heteroepitaxial nucleation mechanisms simultaneously. The adsorption poisoning mechanism implies that Ca preferentially adsorbs on the Mg-terminated surfaces of Mg2Si(100) and Mg2Si(111). Meanwhile, the heteroepitaxial nucleation mechanism indicates the nucleation interface of Mg2Si(100)//CaSi2(001), where the Mg2Si(100) surface is terminated by Si, and the CaSi2(001) surface is terminated by Ca, with stacking modes of Si-Top and Si-Center. In addition, the inclusion of Ca in the primary Mg2Si phase through heteroepitaxial nucleation not only leads to refinement of the primary Mg2Si phase but also displays excellent interface mechanical properties, which suggests that Ca can be considered as an optimal modifier for the primary Mg2Si phase. This study provides a fundamental insight into the role of Ca in modifying the primary Mg2Si phase and has potential implications for the development of Si-containing magnesium alloys.