First-principles Approach Research Articles

A self-adaptive first-principles approach for magnetic excited states

The profound impact of excited magnetic states on the intricate interplay between electron and lattice behaviors in magnetic materials is a topic of great interest. Unfortunately, despite the significant strides that have been made in first-principles methods, accurately tracking these phenomena remains a challenging and elusive task. The crux of the challenge that lies before us is centered on the intricate task of characterizing the magnetic configuration of an excited state, utilizing a first-principle approach that is firmly rooted in the ground state of the system. We propose a versatile self-adaptive spin-constrained density functional theory formalism. By iteratively optimizing the constraining field alongside the electron wave function during energy minimization, we are able to obtain an accurate potential energy surface that captures the longitudinal and transverse variations of magnetization in itinerant ferromagnetic Fe. Moreover, this technique allows us to identify the subtle coupling between magnetic moments and other degrees of freedom by tracking energy variation, providing new insights into the intricate interplay between magnetic interactions, electronic band structure, and phonon dispersion curves in single-layered CrI3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$\\mathrm{CrI} _{3}$\\end{document}. This new methodology represents a significant breakthrough in our ability to probe the complex and multifaceted properties of magnetic systems.

Hydrogen storage capacity and reversibility of BC3N2 monolayers with and without Li decoration insights from first-principles methods

The identification and development of novel materials for effective hydrogen storage is of paramount significance in the context of hydrogen-based economies. In this investigation, the hydrogen storage capabilities of the BC3N2 monolayer both with and without lithium (Li) decoration was examined by utilizing first-principles approaches. The findings indicate that the BC3N2 monolayer possesses a notable hydrogen storage capacity of 13.8 wt%. However, it is noteworthy that the average adsorption energy of H2 molecules is approximately 0.16 eV, resulting in a relatively low desorption temperature. This characteristic poses a significant obstacle to the practical utilization of the BC3N2 monolayer. Decoration of the BC3N2 monolayer with Li atoms was shown to be thermodynamically beneficial and resulted in non-aggregation on the surface. The monolayers of BC3N2 decorated with Li exhibited a remarkably high capacity for hydrogen adsorption, reaching 9.9 wt%. The ideal adsorption energies for this system were found to be in the range of 0.32–0.47 eV/H2. These results exceed the target set by the US DOE (6.5 wt%) and demonstrate superior performance compared to the majority of CN-based monolayers. The electrostatic properties of the interaction between H2 molecules and the monolayer decorated with Li were verified through the analysis of ELF and DOS. The reversibility of H2 molecule adsorption and desorption on Li-decorated BC3N2 monolayers has been demonstrated through the analysis of occupation number and desorption temperature under practical working conditions. The results of the study indicate that the incorporation of Li into BC3N2 monolayers has great potential as a highly efficient medium for hydrogen storage.

Ab-Initio Investigation into the Physical Characteristics of CuInSe2 and CuInTe2 Compounds

In this study, an analysis of chalcopyrite compounds CuInTe2 and CuInTe2 is presented, with a focus on their electronic, structural, optical, and thermal properties. The full-potential linearized augmented plane wave (FP-LAPW) method is employed for the investigation of these properties, based on a first-principles approach rooted in density functional theory (DFT). Two distinct approximations for the exchange and correlation potential, namely the WC-GGA and mBJ-GGA approximations, are considered in our calculations to ensure a robust and accurate examination of the materials under scrutiny. The findings obtained closely align with previously established theoretical and experimental data, thereby validating the reliability of our computational methodology. It is noteworthy that a novel dimension is introduced by this study, as the influence of both pressure and temperature on the thermal parameters of CuInTe2 and CuInTe2 compounds is explored. This facet of the research is distinguished by its innovative nature, as there is no prior record, to the best of our knowledge, of a similar analysis in the existing literature. The thermal properties are deemed of paramount significance, particularly in the context of crystal growth process optimization and the prediction of performance under extreme thermodynamic conditions.

Exploring novel Zr2GeX (X = C, N, F) MAX phases by first-principles approach

In recent years, there has been a surge of interest in the thermodynamically stable nanolaminate ternary carbides/nitrides known as MAX phases. In this first-principles research work, we focus on the MAX phases with a particular emphasis on Zr2GeX (X = C, N, F) compounds. These novel Zr2GeX compounds exhibited considerable values of cohesive energy, demonstrating stability comparable to well-established MAX compounds. Our calculations for the structural parameters of Zr2GeX agree well with the literature, indicating the reliability of our results. The absorption coefficients for ultraviolet (UV) light are approximately 105/cm and 106/cm, respectively, highlighting their significance for energy harvesting devices. Additionally, these metallic compounds demonstrate impressive reflectivity, reflecting over 50% of infrared and visible light. Similarly, they exhibit the highest refraction for infrared light, with a significant decrease in refraction for visible and UV light. Consequently, the transparency of Zr2GeX compounds diminishes, rendering them opaque against UV light and highly likely to absorb most incident UV radiation. Results presented in this paper highlight the potential applications of Zr2GeX MAX phases for optoelectronic devices due to their exceptional electronic and optical properties.

First-Principles Approach to Elucidating Significant Rectification Ratios in Oppositely Charged Dipeptides

First-Principles Approach to Elucidating Significant Rectification Ratios in Oppositely Charged Dipeptides

Thermoelectric properties of M[formula omitted]AgAlBr[formula omitted] (M = K, Rb, Cs) double perovskites: A first principles study

Structural, electronic, and transport properties of aluminum-based double halide perovskite M2AgAlBr6 (M = K, Rb, Cs) are here subject of investigation, using first-principles approaches based on density functional theory, as implemented in the plane-wave pseudopotential method. Thermoelectric performance was evaluated by analyzing the results of first-principles band structure calculations and semiclassical Boltzmann theory within the constant relaxation time approximation. The theoretically predicted values for the electronic contribution for the figure of merit are close to 1.0 at room temperature, suggesting that all compounds studied are promising candidates for applications in thermoelectric devices.

First-principles study on the adsorption of divalent heavy metal ions by black phosphorus in water

With the rapid development of electronics, the application and research of two-dimensional materials have been at the forefront of the world’s scientific research. Black phosphorus (BP) has the advantages of large specific surface area, anisotropy, band tunability, high electrical conductivity and high theoretical specific capacity, which make it very promising for research in the fields of medicine, aerospace and electrochemistry. This paper calculates the electronic structure and adsorption properties of BP in water for different heavy metal ions of Pb[Formula: see text], Hg[Formula: see text] and Cd[Formula: see text], including adsorption energy, bandgap, electron density and Mulliken population analysis, based on the first-principles approach of density generalized theory. First principles are quantum mechanical calculations based on density functional theory (DFT), which is a dominant well-developed method in the field of materials simulations, with low errors and high efficiency, especially in systems containing metallic particles. The results showed that the Pb[Formula: see text] adsorption system in water was more stable than the Hg[Formula: see text] adsorption system and the Cd[Formula: see text] adsorption system. The bandgap values of 0.617, 0.785 and 0.715[Formula: see text]eV of BP after adsorption of Pb[Formula: see text], Hg[Formula: see text] and Cd[Formula: see text] in water are smaller compared to 0.891[Formula: see text]eV of intrinsic BP, and its properties change from direct bandgap semiconductor to indirect bandgap semiconductor. The higher the stability of a system for the adsorption of different heavy metal ions by BP, the higher the internal electron activity of the adsorption system and the amount of electron transfer. Meanwhile, it is concluded that the electrons mainly transfer from P to heavy metal ions in all the adsorption systems. The electron transfer of the BP-Pb[Formula: see text], Hg[Formula: see text], and Cd[Formula: see text] adsorption system occurs mainly in the p, s, and s/p orbitals, respectively. The above content investigated the electronic structure changes and internal electron transfer of heavy metal ions adsorbed by black phosphorus in water, expecting to provide a new reference basis for the detection of heavy metal ions in industrial wastewater using black phosphorus.

Study of electronic and magnetic properties of Mn-doped KNbO3: A first-principles approach

Changes in the electronic structure of Mn-doped KNbO3 have been studied by first-principles calculations, using the projector-augmented-wave method, within the generalized gradient approximation with on-site Hubbard-U potential (GGA + U), for the exchange-correlation potential. In our study, we analyze different Mn-dopant concentrations, namely 2.5, 5, and 10 %, with Mn entering Nb, K or both sites. Our results show that all doped structures acquire a ferromagnetic character. When Mn enters in Nb or K sites, the structures acquire a metallic character and when Mn enters in both Nb and K, the structures conserve a semiconductor character. The site-decomposed partial density of states shows that the metallic character comes from an up-shift in energy of O-p orbitals when Mn enters Nb sites and a down-shift energy when Mn enters K sites. Furthermore, when Mn enters in both Nb and K sites, a combination of the former cases takes place, resulting a structure with a semiconductor character. Analyzing the formal oxidation states of component atoms allows us to explain changes in electrical and magnetic properties.

Structure and mechanical properties of novel lightweight refractory high entropy alloys NbMoTiZr-(Al/V): a combined first principles and experimental study

NbMoTaW refractory high entropy alloy (RHEA) has excellent high temperature mechanical properties, but low room temperature ductility and high density severely limit its practical applications. In the present work, to overcome this deficiency, the composition was adjusted, and the mechanical properties of four novel as-cast NbMoTiZr-(Al/V) lightweight refractory high entropy alloys (LRHEAs) were investigated by theoretical calculations combined with experimental methods. The first-principle calculations approach based on density functional theory predicts the mechanical properties of LRHEAs and explains the alloying effects at the atomic and electronic levels. The body-centered-cubic (BCC) phase structure of the alloys were predicted on the formation enthalpy and cohesive energy, as well as empirical parameters such as ΔSmix, ΔHmix, VEC, and the atomic size difference, in conjunction with CALPHAD and XRD. The microstructure of the LRHEAs were also analyzed by SEM. The experimental results, along with the calculated elastic constants and moduli, show significant improvement in the strength and ductility of NbMoTiZr-(Al/V) LRHEAs compared to NbMoTaW RHEA. LRHEAs exhibit elastic anisotropy and are therefore more suitable for use in engineering applications. The strengthening mechanisms of the alloys were analyzed in terms of total and partial densities of states, overlapping Mulliken population, charge density contour and atomic distances. The increased plasticity of LRHEAs is mainly due to the formation of Ti-Ti, Zr-Zr and Zr-Al metallic bonds in the alloys. The calculated results agree with the experimental results, indicating that first-principles calculations are an effective method for predicting the improved properties of lightweight refractory high-entropy alloys. The present work provides a good guideline for the design and research of lightweight refractory high entropy alloys.

First-Principles Approaches to Magnetoelectric Multiferroics

Magnetoelectric multiferroics, which display both ferroelectric and magnetic orders, are appealing because of their rich fundamental physics and promising technological applications. The revival of multiferroics since 2003 led to a comprehensive understanding of the mechanisms that facilitate the coexistence of electric and magnetic orders and conceptually new design strategies for device architectures, which brought us an important step closer to multiferroic-based technology. In the past thirty years, first-principles calculations based on the laws of quantum mechanics played a crucial role in understanding the electronic, magnetic, and structural properties of multiferroics and guided the design of new multiferroics with improved properties. In this review, we provide a comprehensive overview of first-principles approaches to magnetoelectric multiferroics, especially in low-dimensional forms. In particular, we discuss methods to build an effective Hamiltonian from first principles for magnets, ferroelectrics, and multiferroics. The recently developed machine learning potential approach for multiferroics is also outlined. Furthermore, we present the unified model for spin-induced ferroelectricity and methods for computing the linear magnetoelectric coupling tensor. Finally, recent progress in multiferroic systems and the applications of first-principles approaches to these systems are reviewed.

First-principles Approach to Image Lightness Processing

First-principles Approach to Image Lightness Processing

First-principles study of the structural, mechanical, dynamical, and transport properties of Cs2NaInX6[X = Br,I] for thermoelectric applications

Thermoelectricity generation techniques utilized for conversion of waste heat into electric power are currently gaining prominence. It is necessary that for improved efficiency, the materials used for such applications should have a high thermoelectric figure of merit (ZT) and appropriate stability. In this study, the properties of Cs2NaInX6 double perovskites (DPs) were examined using a first-principles approach to ascertain their suitability as thermoelectric materials. The findings revealed that the materials are mechanically stable according to the Born stability criteria for cubic crystals. They were also observed to be anisotropic given isotropic values of 0.702 and 0.662 for Cs2NaInBr6 and Cs2NaInI6 DPs respectively. Phonon calculations indicate soft modes at the Brillouin zone boundary and center (Γ) for Cs2NaInI6 DP, which suggests ferroelectric and anti-ferroelectric distortions. Similarly for Cs2NaInBr6 DP, the soft modes were exclusively found at the BZ center (Γ), suggesting ferroelectric distortion. The transport coefficient properties calculated are used for the determination of the ZT values. The calculated values of ZT at ambient temperature are of the order 1.0 for all the DPs which is high enough for thermoelectric applications suggesting that they may be potential thermoelectric materials

Black phosphorene/SnSe van der Waals heterostructure as a promising anchoring anode material for metal-ion batteries

Black phosphorene (BP) is a glowing two-dimensional semiconducting layer material for cutting-edge microelectronics, with high carrier mobility and thickness-dependent band gap. Here, based on van der Waals (vdW)-corrected first-principles approaches, we investigated stacked BP/tin selenide (BP/SnSe) vdW heterostructure as an anode material for metal ion batteries, which exhibits a significant theoretical capacity, along with relatively durable binding strength compared to the constituent BP and SnSe monolayers. Our calculations demonstrated that the Li/Na adatom favors insertion into the interlayer region of BP/SnSe vdW heterostructure owing to synergistic interfacial effect, resulting in comparable diffusivity to the BP and SnSe monolayers. Subsequently, the theoretical specific capacities for Li/Na are found to be as high as 956.30 mAhg−1 and 828.79 mAhg−1, respectively, which could be attributed to the much higher storage capacity of Li/Na adatoms in the BP/SnSe vdW heterostructure. Moreover, the electronic structure calculations reveal that a large amount of charge transfer assists in semiconductor-to-metallic transition upon lithiation/sodiation, ensuring good electrical conductivity. These simulations verify that the BP/SnSe vdW heterostructure has immense potential for application in the design of metal-ion battery technologies.

Physical properties of different polymorphs of sulfur doped ZnO studied in the framework of first-principles approaches

Various physical properties of pure and sulfur-doped zinc oxide in the germanium phosphide (GeP), cesium chloride (CsCl), and nickel arsenide (NiAs) type structures are studied using the first-principles approaches in this research. The structural characteristics of the ZnOS alloys in GeP, CsCl, and NiAs type polymorphs show a slight deviation from Vegard's law, which is consistent with the available literature. It is observed that the electronic band structures of the ZnOS alloys show an exciting impact of sulfur (S) substitution in the ZnO. The ZnOS alloys, in CsCl type structure, display their metallic character. The static dielectric constants of the GeP, CsCl, and NiAs type’s polymorphs demonstrate that with increasing S concentration, polarization is enhanced. Moreover, the CsCl type phase of the ZnOS alloys exhibits the maximum value of the static dielectric constant along with showing metallic character. The optical results highlight the potential of S-doped ZnO in these structures as the highest absorption, reflectivity, and conductivity peaks shift towards low photon energies. The examination of the absorption spectra demonstrates that GeP-type ZnOS alloys are suitable for infrared to visible regime applications. On the other hand, NiAs-type ZnOS alloys are appropriate for use in the visible light regime.

DFT Investigation of the Structural, Electronic, and Optical Properties of AsTi (Bi)-Phase ZnO under Pressure for Optoelectronic Applications

Pressure-induced phases of ZnO have attracted considerable attention owing to their excellent electronic and optical properties. This study provides a vital insight into the electronic structure, optical characteristics, and structural properties of the AsTi (Bi) phase of ZnO under high pressure via the DFT-based first-principles approach. The phase transformation from BN(Bk) to the Bi phase of ZnO is estimated at 16.1 GPa using local density approximation, whereas the properties are explored precisely by the hybrid functional B3LYP. The electronic structure exploration confirms that the Bi phase is an insulator with a wider direct bandgap, which expands by increasing pressure. The dielectric function evidenced that the Bi phase behaves as a dielectric in the visible region and a metallic material at 18 eV. Optical features such as the refractive index and loss function revealed the transparent nature of the Bi phase in the UV range. Moreover, the considered Bi phase is found to possess a high absorption coefficient in the ultraviolet region. This research provides strong theoretical support for the development of Bi-phase ZnO-based optoelectronic and photovoltaic devices.

Electrical Conductance and Thermopower of β-Substituted Porphyrin Molecular Junctions─Synthesis and Transport.

Molecular junctions offer significant potential for enhancing thermoelectric power generation. Quantum interference effects and associated sharp features in electron transmission are expected to enable the tuning and enhancement of thermoelectric properties in molecular junctions. To systematically explore the effect of quantum interferences, we designed and synthesized two new classes of porphyrins, P1 and P2, with two methylthio anchoring groups in the 2,13- and 2,12-positions, respectively, and their Zn complexes, Zn-P1 and Zn-P2. Past theory suggests that P1 and Zn-P1 feature destructive quantum interference in single-molecule junctions with gold electrodes and may thus show high thermopower, while P2 and Zn-P2 do not. Our detailed experimental single-molecule break-junction studies of conductance and thermopower, the latter being the first ever performed on porphyrin molecular junctions, revealed that the electrical conductance of the P1 and Zn-P1 junctions is relatively close, and the same holds for P2 and Zn-P2, while there is a 6 times reduction in the electrical conductance between P1 and P2 type junctions. Further, we observed that the thermopower of P1 junctions is slightly larger than for P2 junctions, while Zn-P1 junctions show the largest thermopower and Zn-P2 junctions show the lowest. We relate the experimental results to quantum transport theory using first-principles approaches. While the conductance of P1 and Zn-P1 junctions is robustly predicted to be larger than those of P2 and Zn-P2, computed thermopowers depend sensitively on the level of theory and the single-molecule junction geometry. However, the predicted large difference in conductance and thermopower values between Zn-P1 and Zn-P2 derivatives, suggested in previous model calculations, is not supported by our experimental and theoretical findings.

Exploration of the structural, optoelectronic, magnetic, elastic, vibrational, and thermodynamic properties of molybdenum-based chalcogenides A2MoSe4 (A =Li, K) for photovoltaics and spintronics applications: a first-principle study.

In the present work, the cubic phase of the chalcogenide materials, i.e., A2MoSe4 (A =Li, K) is examined to explore the structural, optoelectronic, magnetic, mechanical, vibrational, and thermodynamic properties. The lattice parameters for Li2MoSe4 are found to be a= 7.62 Å with lattice angles of α=β=γ=90° whereas for K2MoSe4, a= 8.43 Å, and α=β=γ=90°. These materials are categorized as semiconductors because Li2MoSe4 and K2MoSe4 exhibit direct energy band gap worth 1.32 eV and 1.61 eV, respectively through HSE06 functional. The optical analysis has declared them efficient materials for optoelectronic applications because both materials are found to be effective absorbers of ultraviolet radiations. These materials are noticed to be brittle while possessing anisotropic behavior for various mechanical applications. The vibrational properties are explored to check the thermal stability of the materials. On the basis of thermodynamics and heat capacity response, Li2MoSe4 is more stable than K2MoSe4. The results of our study lay the groundwork for future research on the physical characteristics of ternary transition metal chalcogenides (TMC). These physical properties are explored for the first time while using a first-principles approach based on density functional theory (DFT) in the framework of Cambridge Serial Total Energy Package (CASTEP) by Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) functional. However, GGA+U and HSE06 are also employed to improve electronic properties. Kramers-Kronig relations are used to evaluate the dielectric function with a smearing value of 0.5 eV. Voigt-Reuss-Hill approximation is used for seeking the elastic response of these materials. The thermodynamic response is sought by harmonic approximation. The density functional perturbation theory (DFPT) approach is used for investigating atomic vibrations.

Physical properties 211-type of MAX phases based on Mn2AlX (X = C, N, and F) through first-principles approaches

Over the past two decades, researchers have shown great interest in the MAX phases owing to their intriguing combination of metallic and ceramic properties. In this study, we analyzed the physical properties of the 211-type MAX phases exploiting the Mn2AlX (X = C, N, and F) as base materials. Our main focus lies on exploring their physical characteristics encompassing the lattice parameters, electronic properties, magnetic behavior, and optical properties by employing the “density functional theory (DFT) based full-potential linearized augmented plane wave (FP-LAPW) method”. The obtained results are found consistent with the literature, affirming the reliability of the selected approach. The cohesion of these MAX phases has been verified by calculating their cohesive energies recorded as 5.12 eV, 9.30 eV, and 3.77 eV for Mn2AlC, Mn2AlN, and Mn2AlF, respectively. The Mn2AlX demonstrated non-uniform distributions of the density of states (DOS) that has tuned substantial ground states magnetization with magnitudes of 6.228 μβ, 6.343 μβ, and 13.706 μβ per unit cell for Mn2AlC, Mn2AlN, and Mn2AlF, respectively. These MAX phases have also demonstrated notable variations in their optical absorption and reflectivity spectra, which are dependent on the crystallographic orientation. The static refractive indices for x-component (z-component) recorded for Mn2AlC, Mn2AlN, and Mn2AlF are 8.391 (8.612), 9.162 (6.834), and 5.031(4.219), respectively. This highlights the considerable role of crystallographic orientation on their optical characteristics and also suggests their promising use in photovoltaic systems and other optical devices.

Exploration of Solid Solutions and the Strengthening of Aluminum Substrates by Alloying Atoms: Machine Learning Accelerated Density Functional Theory Calculations.

In this paper, we studied the effects of a series of alloying atoms on the stability and micromechanical properties of aluminum alloy using a machine learning accelerated first-principles approach. In our preliminary work, high-throughput first-principles calculations were explored and the solution energy and theoretical stress of atomically doped aluminum substrates were extracted as basic data. By comparing five different algorithms, we found that the Catboost model had the lowest RMSE (0.24) and lowest MAPE (6.34), and this was used as the final prediction model to predict the solid solution strengthening of the aluminum matrix by the elements. Calculations show that alloying atoms such as K, Na, Y and Tl are difficult to dissolve in the aluminum matrix, whereas alloy atoms like Sc, Cu, B, Zr, Ni, Ti, Nb, V, Cr, Mn, Mo, and W exerted a strengthening influence. Theoretical studies on solid solutions and the strengthening effect of various alloy atoms in an aluminum matrix can offer theoretical guidance for the subsequent selection of suitable alloy elements. The theoretical investigation of alloy atoms in an aluminum matrix unveils the fundamental aspects of the solution strengthening effect, contributing significantly to the expedited development of new aluminum alloys.

First-principles approach to closing the 10–100 eV gap for charge-carrier thermalization in semiconductors

First-principles approach to closing the 10–100 eV gap for charge-carrier thermalization in semiconductors