First-principles Investigation Research Articles

Transition Metal (Cu, Pd, and Ag)-Modified Nb2S2C Monolayer for Highly Efficient Catechol Sensing: A First-Principles Investigation.

Motivated by recent advancements and the escalating application of two-dimensional (2D) gas or molecule sensors, this study explores the potential of the 2D Nb2S2C monolayer for detecting biomolecule catechol (Cc), whose excess concentration is highly dangerous to living beings. We use first-principles density functional theory (DFT) calculations to assess the Cc sensing performance of pure and transition metal (TM = Cu, Pd, Ag)-modified Nb2S2C monolayers. The Nb2S2C monolayer belonging to the new class of synthesized 2D materials, TM carbo-chalcogenides (TMCC), combines distinctive properties from both TM dichalcogenides and TM carbides and exhibits physisorption (-0.66 eV) toward the Cc molecule. Notably, the surface modifications with these TMs significantly enhanced the adsorption energy of Cc. The chemisorption of the Cc molecule on the Pd to Cu-modified monolayer is demonstrated with adsorption energies ranging from -1.09 to -1.3 eV and is due to the robust charge transfer and orbital interactions between the valence orbitals of TMs and Cc. In addition, the modification of the surface by TM leads to an increased work function sensitivity toward the Cc molecule. The study establishes the thermal stability at 300 K and dynamic stability of TM-Nb2S2C through ab initio molecular dynamics (AIMD) simulations and Phonon calculations, respectively. The theoretical estimation of achievable recovery time at 400 and 450 K for Pd and Ag and at 500 K for the Cu-modified Nb2S2C monolayer, respectively, confirms the potential practical application of the sensor for Cc detection. These compelling characteristics position the Nb2S2C monolayer as a promising nanomaterial for detecting Cc molecules in the environment.

Investigation of TM (TM=Mg, Cu) doping effect on the luminescence performance of CsPbCl3 from a first-principles investigation

The inorganic perovskite CsPbCl3 has raised great concern in recent years due to its great tunability of luminescence properties via impurity doping. However, the blue-emitting mechanism of the impurity-doped CsPbCl3 is unexplored. In this work, we focus on the structural, electronic, and optical properties of CsPb1-x TM x Cl3 (TM=Mg, Cu; x = 0, 0.037, 0.074) based on the first-principles calculations. It is indicated that TM doping decreases the lattice parameter, deforms octahedral structure, and improves the stability of CsPbCl3. The increased direct bandgap values and unique TM energy levels occupation show that the doped systems behave only blue-emitting well. The Mg-s and Cu-3d (eg) states out the bandgaps are close to the valence band edge and conduction band edge respectively, both promoting the carrier radiation recombination. Furthermore, the density of states analyses demonstrates that the enhanced emission of TM-doped CsPbCl3 benefits from the TM different electronic configurations and the different hybridization ways (Mg 3s/Cl 3p, Cu eg/Cl 3p), producing more carriers with increasing x respectively. The obtained optical properties imply that the TM-doped systems exhibit significant optical absorption and high carrier mobilities, promoting excellent luminescence efficiency. Our work explains the blue-emitting mechanism of the TM-doped CsPbCl3, providing a prospective strategy for designing highly efficient blue-emitting devices for optoelectronic applications based on the available parent materials by modulating the bandgap, synergistic relation of impurity energy level and band edge, and optical property.

Correlations, disorder, and multimagnon processes in terahertz spin dynamics of magnetic nanostructures: A first-principles investigation

Correlations, disorder, and multimagnon processes in terahertz spin dynamics of magnetic nanostructures: A first-principles investigation

First-principles investigation on the effect of Nb and Ta doping on the hydrogen storage performance of ZrCo

The ZrCo alloy has demonstrated significant potential in the storage of hydrogen and its isotopes, but there are still some issues such as insufficient dynamic properties. In this paper, the impact of Nb/Ta doping on the hydride stability of ZrCo was examined based on the density functional theory, and the improvement of H diffusion through Nb/Ta doping was investigated. The focal point lies in exploring the influence of Nb/Ta doping on the alloy’s resistance to poisoning and disproportionation. The results demonstrate that the crystal lattice maintains mechanical and thermodynamic stability even after Nb/Ta doping. Nb/Ta doping induces lattice contraction in ZrCo-Hx (x = 1.0–3.0) and reduce the enthalpy of formation, thereby facilitating cyclic hydrogen storage. Additionally, Nb/Ta doping enhances the diffusion performance of H atoms within O-containing lattice, improving the alloy’s resistance to poisoning. Furthermore, Nb/Ta doping lowers the energy barrier of H atoms escape from 8e sites, promoting anti-disproportionation.

First-Principles Investigation of the Effects of UF4 and ThF4 Fuels on the Structural, Dynamic, and Thermodynamic Properties of LiF-NaF.

An in-depth understanding and characterization of molten salt properties are necessary for the optimized design, efficient operation, and safety assurance of molten salt reactors (MSRs). Investigating molten salt properties in experimental settings can be challenging and time-consuming due to the high temperatures of interest, the salt's corrosiveness, purity and composition control, and health and safety concerns. Therefore, it is beneficial to perform computational screening to assist in the ultimate experimental measurements. Herein, we used first-principles molecular dynamics simulations to calculate several thermophysical, structural, and dynamic properties of eutectic LiF-NaF with fuel additives UF4 and ThF4. We found that with the incorporation of uranium or thorium, a prepeak appears in the structure factor, indicative of a medium-range structural ordering. Furthermore, we explore the mechanism through which these structural changes enhance shear stress correlations, thereby increasing the salt's viscosity. This work highlights the importance of studying the atomic-scale structure of molten salts and how the addition of fuel elements can substantially affect it.

First-principles investigations on magnesium oxynitride for electronic, thermoelectric, and optical applications

First-principles investigations on magnesium oxynitride for electronic, thermoelectric, and optical applications

Optoelectronic Property Exploration in SnS2 Monolayer and Homojunctions with Non-metallic Element (B, C, N) Doping: A First-Principles Investigation

Optoelectronic Property Exploration in SnS2 Monolayer and Homojunctions with Non-metallic Element (B, C, N) Doping: A First-Principles Investigation

First-Principles Investigations of Structural, Elastic, Mechanical Properties of ZnCr2S4 under Pressure

First-Principles Investigations of Structural, Elastic, Mechanical Properties of ZnCr2S4 under Pressure

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.

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.

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.

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.

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.