Plane Wave Method Research Articles

Study of lanthanide based Ln2MgSe4 (Ln = Er, Pm) spinels for spintronic and optoelectronic applications

Abstract Herein, the full potential linearized augmented plane wave (FP-LAPW) method within the framework of density functional theory (DFT) is used to examine the physical features of Ln2MgSe4 (Ln = Er, Pm) spinel selenides. Exchange correlation energies are estimated through modified Becke–Johnson potential (mBJ). Band structures (BS) and density of states (DOS) data proved that Er2MgSe4 is ferromagnetic (FM) semiconductor while Pm2MgSe4 is half metallic (HFM) ferromagnetic in nature. The Er-f contributed majorly to the vicinity of Fermi level for both compounds. The structural stability is determined through calculating the tolerance factor and geometry optimization, while thermodynamical stability has been realized by computing the formation enthalpy. Furthermore, various optical parameters have been computed which describe the considered materials’ response to incident light. Our study explored the physical properties of two Ln based spinels which are found to have potential for being used in various optoelectronic and spintronic devices.

First principle insight of CaBS[formula omitted] (B= Sn, Zr and Hf) chalcogenide perovskite as eco-friendly material for photovoltaics

Lead-free perovskite-type materials, renowned for their easy processing and tunable bandgaps, have emerged as a cost-effective alternative for fabricating high-efficiency tandem solar cells. Utilizing density functional theory (DFT) combined with the full-potential linearized augmented plane wave (FP-LAPW) method and the modified Becke-Johnson exchange potential (TB-mBJ), this study investigates the potential of CaBS3 (B = Zr, Hf, and Sn) compounds as promising absorbers for next-generation tandem applications. Our results demonstrate that CaBS3 compounds exhibit semiconducting properties with direct bandgaps. This study investigates the unique properties of CaBS3 perovskites, revealing their potential to enhance the efficiency of next-generation photovoltaic devices. Our findings demonstrate that CaZrS3 exhibits a remarkable Seebeck coefficient of up to 3200 μV/K, indicating superior p-type conduction and enhanced thermoelectric efficiency. Furthermore, the direct bandgaps and ambipolar conductive behavior of these materials position them as strong candidates for photovoltaic applications. Notably, a four-terminal tandem solar cell configuration comprising CaZrS3 and CaSnS3 achieves a peak conversion efficiency of 55.5% at an absorber thickness of 500 nm, surpassing the traditional Shockley-Queisser limit. These results underscore the promising capabilities of CaBS3 perovskites in advancing renewable energy technologies, paving the way for innovative designs in solar energy solutions.This investigation lends empirical credence to the optimization of tandem cell designs, thus catalyzing advancements in next-generation photovoltaic technologies.

First-principle study origin of ferromagnetism in non-magnetic perovskite BaSnO3 doped with 2p-X (X=C, N)

In this study, our goal is to analyze the origin of magnetization in non magnetic cubic structure perovskite BaSnO3 doped with 2p-X (X=C, N) using the full potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT). For the exchange and correlation potential we have applied the generalized gradient approximation (GGA) and the GGA plus-modified Becke-Johnson potential (mBJ-GGA). The results show that BaSnO3 doped with C then with N and finally with C and N exhibit half-metallic ferromagnetism behavior with the integer magnetic moment of 1, 2 and 3 μB per cell respectively. The origin of the ferromagnetism that occurs within these compounds is mainly caused by the p-p hybridization between 2p-impurities and its neighboring oxygen atoms. These results allowed to conclude that doped perovskite could provide a new type of materials, called half-metallic for future spintronic devices.

The Structural, Elastic, and thermodynamic properties of Sr2P7Br Double Zintl salt with heptaphosphanortricyclane configuration

We investigated the effects of externally applied pressure on the Sr2P7Br compound’s properties, specifically its crystalline structure, elasticity, and thermodynamics. This investigation was carried out using the pseudopotential plane wave method within the framework of density functional theory. We used the well-known PBEsol variant of the exchange–correlation general gradient approximation specifically designed for solid-state analysis. This is the first endeavor to investigate the effects of pressure on the Sr2P7Br material using a theoretical approach. The computed equilibrium structural parameters closely match the relevant experimental counterpart values. The determined elastic constants, obtained under both ambient pressure and hydrostatic pressures up to 18 GPa, satisfy the mechanical stability requirements. Based on the computed Pugh’s ratio, Cauchy pressure, and Poisson’s ratio, it can be concluded that the Sr2P7Br compound exhibits ductile behavior. The polycrystalline elastic moduli, including the isotropic bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio, at ambient pressure and under pressure effects, were derived from the single-crystal elastic constants. Additionally, associated parameters, such as average sound velocity, Debye temperature, minimum thermal conductivity, and Vickers hardness, were examined under pressure influences. The quasi-harmonic Debye approximation was used to investigate the relationship between temperature and some macroscopic physical parameters, such as lattice parameter, bulk modulus, Debye temperature, volume thermal expansion coefficient, and isobaric and isochoric heat capacities, at fixed pressures of 0, 4, 8, 12, and 16 GPa. The results derived from the elastic constants exhibit substantial concordance with those computed using the Debye quasi-harmonic model, thereby validating the reliability of our findings.

Complex band structure of two-dimensional thermal wave crystals

We investigate the complex band structure of temperature oscillations in a two-dimensional thermal wave crystal. We use the Cattaneo-Vernotte heat model to describe the thermal properties. We apply the plane wave method to calculate the complex band structure of a square lattice composed of an infinite array of square bars. We find that a complete band gap exists across the whole Brillouin zone, where temperature oscillations are forbidden. This has potential applications in thermal management, thermal cloaking, and other areas.

Optoelectronic and thermodynamic properties of the Yttrium filled skutterudite YFe4P12

In this work, we sought to understand the structural, electronic, optical, and thermodynamic properties of the compound YFe4P12 using the full-potential and linear augmented plane-wave method (FP-LAPW) based on density functional theory (DFT), our calculation of the lattice parameter of this compound YFe4P12 is reasonably in good agreement with the experimental results. Calculations carried out on the electronic band structure showed that the YFe4P12 compound is classified as a direct-gap Half- half-metallic in the minority spins. Moreover, optical properties, such as the optical absorption coefficient, real and imaginary parts of the dielectric function, optical conductivity, refractive index, and optical reflectivity have been studied. The effects of pressure and temperature on the lattice parameter, heat capacities, coefficients of thermal expansion, entropy, and Debye temperature were explored using the quasi-harmonic Debye model.

Theoretical aspects of structure, electronic, optical and elastic properties of Ca(1-x)CxSe mixed alloys in binary and ternary phases

The structural, optoelectronic, and elastic properties of Carbon doped Calcium Selenide binary and ternary semiconductor alloys with the general form of Ca(1-x)CxSe, 0 ≤ x ≤ 1 in B1 and B3 phases have been scrutinized adopting augmented plane wave plus local orbital methods within density functional theory applying different approximations like the Local density approximation (LDA), Wu-Cohen-Generalized Gradients Approximation (WC-GGA) and modified Becke-Johnson (mBJ). Structural properties summarize the crystal structure, relevant atomic positions, lattice constant, Bulk modulus B0, minimum energy E0, and minimum volume V0. Elastic constants confirm the structure stability of the B1 and B3 phases. The band gap was modified from a wider for appropriate optoelectronic devices application to narrow that enhanced the range of applicability of these binary and ternary semiconductor compounds for optoelectronic device applications. Whereas optical properties which include the study of zero frequency limit of static dielectric constant ε0(ω) with its real and imaginary parts, static refractive index n(0), optical reflectivity R(ω), optical absorption coefficient α(ω), optical conductivity σ(ω), and loss function L(ω) studied comprehensively to get real electrical and optical properties of these materials and give semiconductor market best alternative candidate which shows its effectiveness in the visible, ultraviolet and infrared region of the electromagnetic spectrum. Obtained results compared together and with the available experimental along with theoretical work on these binary and ternary Carbon-doped Alkaline earth Selenide.

Nonlinear plane-wave expansion method for analyzing dispersion properties of piezoelectric metamaterial lattices with encapsulated resonators

Nonlinear plane-wave expansion method for analyzing dispersion properties of piezoelectric metamaterial lattices with encapsulated resonators

A study of optical properties and electron energy loss spectra of ZnS by linear response theory

The linear response theory has been applied to study the optical properties and electron energy loss spectra of ZnS. The ground state is built using the Full-Potential Linearized Augmented Plane Wave method. Thereafter, the electronic properties such as band structure and density of states are calculated. Calculations of electron energy loss spectra and optical properties are performed on the top of these ground state electronic properties. The calculations are performed using three exchange–correlation kernels namely, adiabatic local density approximation, long range contribution, and the bootstrap. The random phase approximation is also considered. An approach proposed by us to find the material dependent parameter α is used in long range contribution kernel to capture more accurate optical properties. Three values of α viz 0.78, 1.09, and 1.22 are considered. It is observed that the α = 0.78 gives very good results. This proposed scheme is found to work very well for ZnS also. The effect of local field and electron–hole interaction on the spectra is examined. For example after incorporating local field effect the high frequency dielectric constant ε∞ [i.e. ε1E→0eV ], reduces by 9.19, 12.26, 13.51 and 11.02% for random phase approximation, adiabatic local density approximation, long range contribution and bootstrap kernel respectively. In EELS plasmon peak positions are found using the three kernels and random phase approximation. A good accord with experimental results is noted after incorporating local field effects. It is observed that local field effect causes redshift of prominent peak (i.e. plasmon peak) in electron energy loss spectra by 0.61 eV.

Elastic mechanical thermodynamic and thermoelectric properties of pristine and titanium doped Mg2Si: a density functional theory study

Herein, we report a systematic investigation of the effect of Titanium doping on the structural, elastic, mechanical, thermodynamic, and thermoelectric (TE) dynamics of Mg2Si Compounds using first-principle investigation. The present study has been carried out using the full potential linearized augmented plane wave method as implemented inWien2kcode undermBJexchange potentials. The investigations revealed that Mg2-xTixSi compounds have structural stability with cubic phase (Fm-3msymmetry) and possess degenerate semiconducting nature. The analysis of elastic constants revealed mechanical stability of the investigated compounds following Born criteria. Thermodynamic investigations have been carried out in the temperature range of 100-1500 K at zero pressure and the quantities like heat capacity, Debye temperature, Grüneisen constant, and thermal expansion coefficient have been critically analyzed. Lastly, the TE performance of Mg2-xTixSi compounds has been predicted by estimating the thermopower (S2σ) and TE figure of merit (zT) in the temperature range of 300-1500 K. The predicted value ofzTmaxfor Mg2-xTixSi compound is 0.67 at 800 K forx= 0.25 titanium content, suggesting materials promising application for TE energy harvesting and mechanical devices.

KCaAs and KCaP: promising half-Heusler compounds for UV protection and thermoelectric applications

This study investigates the structural, electrical, optical, and thermoelectric properties of the half-Heusler compounds KCaAs and KCaP using the Full-Potential Linearized Augmented Plane Wave (FP-LAPW) method within the framework of density functional theory. Our analysis reveals that both compounds exhibit favourable characteristics for high-performance applications. Specifically, KCaAs and KCaP show high static refractive indices and significant reflectivity in the ultraviolet (UV) range, making them ideal for UV protection and optical devices. Thermoelectric analysis indicates that both materials are p-type semiconductors with high Seebeck coefficients at low temperatures, high electrical conductivity, and relatively low thermal conductivity. The temperature-dependent figure of merit ( ZT ) reveals robust thermoelectric performance across a wide temperature range, with maximum ZT values of approximately 0.77 for both compounds. These results suggest that KCaAs and KCaP are promising candidates for thermoelectric applications, offering significant potential for energy conversion and sustainable energy solutions.

Effect of substitutional Sb doping on the structural stability, half-metallicity, elastic properties, electronic properties, and magnetism of the Co₂MnSn full Heusler compound

We conducted Density Functional Theory (DFT) calculations using the full potential linearized augmented plane wave (FP-LAPW) method to modify the Fermi level by introducing Sb doping into Co2MnSn.This was done through the Generalized Gradient Approximation (GGA) and modified Becke-Johnson (mBJ-GGA) formalisms to enhance spin polarization and suggest signs of half-metallicity. For both ferromagnetic and paramagnetic phases, lattice optimization was performed to identify the stable magnetic structure. The results designate that the doped alloys are stable in a ferromagnetic phase with L21 structure. The calculated elastic constants suggest that the doped alloys meet the criteria for mechanical stability. The magnetism in these compounds is primarily due to the localized moments on the Mn and Co atoms. According to mBJ-GGA calculations, the total magnetic moment slightly increases with Sb doping. Analysis of the optical constants revealed the optoelectronic properties, confirming semiconducting behavior. Doping elements to achieve half-metallicity is demonstrated to be an effective method for discovering new materials suitable for spintronics applications.

Investigation of a new group of low band-gap semiconducting double perovskite K2MgSnZ6 (Z = Cl, Br, & I) materials and their structural, electronic, mechanical, and optical behaviors via DFT study

This study focuses on potassium based double perovskite materials, specifically a series of K2MgSnZ6 (Z = Cl, Br, & I) halide materials. For the investigated materials, all primary calculations were performed using the Full-Potential Linearized Augmented Plane-Wave (FP-LAPW) method, supported by density functional theory (DFT), and implemented in the WIEN2k code. The Gold-Schmidt tolerance factor values confirm the structural stability of the compounds, while the negative values of formation energy indicate the feasibility of experimental synthesis of the studied materials. The lattice constants were observed to increase as the halide element at the ‘Z’ position was replaced by one with a larger ionic radius. The recorded band-gap values were 2.60 eV, 2.00 eV, and 1.37 eV for K2MgSnCl6, K2MgSnBr6, and K2MgSnI6, respectively. After calculating the elastic constants for all K2MgSnZ6 (Z = Cl, Br, & I) materials, it was found that they satisfy the primary conditions for Born stability required for cubic-phase materials: (1) C11 > B > C12, (2) C11 + 2C12 > 0, (3) C11 > 0, (4) C44 > 0, and (5) C11–C12 > 0. The optical parameters of the K2MgSnZ6 (Z = Cl, Br, & I) double perovskite materials suggest that these materials could play a significant role in practical applications such as solar cells, UV detectors, and various optoelectronic devices.

Generalizing deep learning electronic structure calculation to the plane-wave basis.

Deep neural networks capable of representing the density functional theory (DFT) Hamiltonian as a function of material structure hold great promise for revolutionizing future electronic structure calculations. However, a notable limitation of previous neural networks is their compatibility solely with the atomic-orbital (AO) basis, excluding the widely used plane-wave (PW) basis. Here we overcome this critical limitation by proposing an accurate and efficient real-space reconstruction method for directly computing AO Hamiltonian matrices from PW DFT results. The reconstruction method is orders of magnitude faster than traditional projection-based methods to convert PW results to the AO basis, and the reconstructed Hamiltonian matrices can faithfully reproduce the PW electronic structure, thus bridging the longstanding gap between the AO basis deep learning electronic structure approach and PW DFT. Advantages of the PW methods, such as high accuracy, high flexibility and wide applicability, thus can be all integrated into deep learning electronic structure methods without sacrificing these methods' inherent benefits. This allows for the construction of large-scale and high-fidelity training datasets with the help of PW DFT results towards the development of precise and broadly applicable deep learning electronic structure models.

Investigation on Lithiated Half‐Heusler Alloy CoMnSi for Lithium‐Ion Batteries

ABSTRACTIn this work, we report on CoMnSi half‐Heusler alloy as a cathode material for secondary lithium‐ion batteries using ab initio methodology based on the density functional theory. The first‐principle calculations have been performed via the Wien2k package, which utilizes the full potential linearized augmented plane wave (FP‐LAPW) method to estimate the stability of the proposed structures and electronic characteristics while considering the exchange and correlation effects within the generalized gradient approximation. This alloy is found structurally stable with better electronic properties and with the alloying of lithium (Li) into the host lattice of CoMnSi, the metallic character is attained for LixCo1−xMnSi (0.125 ≤ x ≤ 1). We propose possible reactions at electrodes during the electrochemical lithiation. The addition of Li in place of the Co atom is found to be an endothermic process. With the increase in lithium concentration, a substantial change in the total and atom projected density of states around the Fermi level is observed. The theoretical maximum specific capacity (CM) and theoretical open circuit voltage (OCV) increase with the increase of lithium concentration in CoMnSi. The CM and OCV values attain a maximum value of around 297 mAh/g and 2.4 Volts for x ≥ 0.75, which means towards the complete conversion of CoMnSi into LiMnSi. The LiMnSi exhibits a similar structure as CoMnSi, which is also advantageous for the overall performance of lithium‐ion batteries to avoid any volumetric change during the charging and discharging cycles. Hence, the proposed half‐Heusler alloys have great potential to be used as a cathode material for lithium‐ion batteries.

Electronic and optical properties of Cr-Mn co-doped in monolayer MoS2: A first-principles study

The effects of Cr-Mn co-doping of neighboring and spacer sites on the electronic and optical properties of monolayer molybdenum disulfide (ML-MoS2) are investigated using a first-principles plane-wave pseudopotential method based on density-functional theory (DFT). The results show that the band structure (BS) and the bandgap of pristine ML-MoS2 are in good agreement with the available experimental and theoretical data. Electronic analysis implies that the bandgap of Cr-Mn co-doped ML-MoS2 is smaller than that of the pristine ML-MoS2 and the bandgap of Cr-Mn co-doped ML-MoS2 at spacer sites is the smallest. Moreover, the ML-MoS2 changes from a direct bandgap to an indirect bandgap semiconductor, which facilitates electron-hole pair transfer. In addition, pristine ML-MoS₂ has no magnetism, while Cr-Mn co-doped ML-MoS2 at neighboring and spacer sites present ferromagnetism. Studies of optical properties have shown that doped ML-MoS2 systems, especially Cr-Mn co-doped at spacer sites, exhibit higher sensitivity to visible and ultraviolet (UV) light along the x-axis as well as to UV light along the z-axis. This suggests the possibility of applications in photodetectors, solar cells, and photocatalysis. It is noteworthy that Cr-Mn co-doping at the spacer sites significantly improves the photovoltaic performance and light utilization efficiency of ML-MoS2 by increasing the dielectric tensor, absorption coefficient, and photoconductivity while decreasing the extinction coefficient compared with pristine ML-MoS2.

DFT study of structural, electronic, magnetic, elastic, and thermoelectric properties of Ta-based half-Heusler alloys CsTaX (X = C, Si, and Ge) for spintronics and thermoelectric technologies

The structural, electronic, elastic, magnetic, and thermoelectric characteristics of three novel Ta-based half-Heusler alloys, CsTaC, CsTaSi, and CsTaGe, have been investigated using the Full-Potential Linearized Augmented Plane Wave (FP-LAPW) method within the density functional theory (DFT). The volume-optimization graphs show that all compounds are stable in the ferromagnetic (FM) phase. Half-Metallicity of these compounds is confirmed by the density of states (DOS) and band structures. The total magnetic moment for CsTaC is 6 μB, and for CsTaX (X = Si, Ge) is 2 μB. The negative pd exchange energy and exchange constants confirm ferromagnetism. The values of Pugh’s ratio (B/G) and Poisson’s ratio (v) reveal that CsTaC is ductile and CsTaX (Si, Ge) is brittle. The thermoelectric response is estimated using the BoltzTraP code, demonstrating that at room temperature, maximum ZT values for CaTaC, CsTaSi, and CsTaGe are 0.99, 0.97, and 0.90, respectively. Consequently, CsTaX (X = C, Si, and Ge) are suitable candidates for spintronic and thermoelectric technologies.

Electronic structure of ultrathin single-walled platinum nanotubes

Using Density Functional Theory based on the plane wave method and linearized augmented cylindrical wave method, and taking into account the spin–orbit interaction, the structural, electronic and spin properties of ultrathin single-walled nanotubes consisting of six platinum rows are obtained. The nanotubes are found to possess metallic electronic mobility, including the nonchiral Pt(6,0) with the largest number (15G0) of ballistic channels. Analysis of the density of electronic states at Fermi level revealed that the chiral Pt(5,1) has a difference in concentration of mobile electrons with opposite spins of 1.42 times, and up to 3–4 times under a weak torsional strain.

Analysis of the electronic nature and transport properties of Co2CrGe, Co2FeGe, and Co2NiGa by computational electronic structure calculations

AbstractElectronic and thermoelectric properties of the full‐Heusler materials Co2CrGe, Co2FeGe, and Co2NiGa are studied, using first‐principles full potential linearized augmented plane waves method. To treat the exchange correlation, Generalized Gradient Approximation parameterized by PBE‐sol with the inclusion of spin polarization is used. The frequency fluctuation order is continual at 300 K after heating to 3 ps with very small distraction in the atomic structure conforming the structure stability of the studied structures. Also inclusion of spin‐orbit coupling effect on density of states undermines significant change in peaks specially d‐states in the materials and caused a degeneracy. Band structure analysis clarified that states crossing the Fermi level have the importance for enhancing the thermoelectric properties of the materials. The topology of the states indicates a gap at the bulk level, which is the unique character of the heavy elements in the materials Co2CrGe, Co2FeGe, and Co2NiGa. Thermoelectric properties are calculated for a temperature of 300 K using semi‐classical Boltzmann's theory implemented in BoltzTraP code. In these calculations, it is found that these materials favor electron doping with having maximum values of ZT in the n‐type region.

Thermoelectric and optoelectronic features of C- and N- doped CsZnBr3 halide perovskite for use in spin filter and energy efficient devices

Present study reports mainly thermoelectric and optical properties followed by its structural, electronic, magnetic properties of CsZnBr3 halide perovskite using full potential linearized augmented plane wave method in the framework of density functional theory. Further we analyzed the impact of C and N on CsZnBr3 for their electronic structure, magnetic nature, thermoelectric, and optical properties. CsZnBr3 under optimum conditions exhibits a non-magnetic phase, which interestingly upon doping of C and N, turns out to be ferromagnetic with magnetic moments of 3.0 and 2.0 μB for CsZnBr2C and CsZnBr2C, respectively. Furthermore, Semiconducting CsZnBr3 exhibits spin filter semiconductor nature with energy band gaps of 1.38↑ and 3.26↓ eV for CsZnBr2C and 2.72↑ and 1.67↓ eV for CsZnBr2N. These doped materials can be used in spintronics as spin-filter devices for lower power consumption leading to more energy-efficient electronics. The thermoelectric parameters as Seebeck coefficient, power factor, thermal conductivity and figure of merit are estimated using BoltzTrap code. The figure of merit value found enhanced from 0.88 to 1.06 with one orientation of spins for CsZnBr2C at high temperature, which suggests its potential use in thermoelectric applications. In optical reference photon energy can be absorbed in UV-region.