Charge Density Contour Research Articles

First principles investigations of linear and nonlinear optical, radiation shielding and thermoelectric properties of the non-centrosymmetric Ba-based chalcogenides Ba2In2X5 (X=S, Te)

We explore the structural, elastic, optoelectronic, Radiation Shielding, and thermoelectric properties of Ba2In2X5 (X = S, Te) using first-principles computations and semi-classical Boltzmann Transport equations. These materials are classified as semiconductors exhibiting band gaps of 2.0 eV and 3.0 eV for both investigated NLO compounds that have more significant direct band gaps of superior optical birefringence and second-order NLO coefficients. The bonding properties have been investigated by analyzing the electron charge density (ECD) contour of the (1 0 1) crystallographic plane. It is clear from the reflectivity spectra that both compounds have a high degree of reflectivity, which could make them useful as UV and visible light shields. From 0 to 14.0 eV, the approximated reflectivity values, R (ω), are displayed against the incident photon energy. Therefore, the reflectivity is around 30 % before E ≈ 12.0 eV and 40 % reflection at ∼13.0 eV. Phase matching is possible for both compounds detected, as shown by the birefringence computations. Furthermore, the radiation shielding properties of Ba2In2S5 and Ba2In2Te5 have been evaluated using Phy-X software, demonstrating their potential effectiveness in medical and nuclear energy applications. The thermoelectric properties display N-type nature at low temperatures when the Seebeck coefficient changes from N to P-type at higher temperature ranges. These compounds have remarkable optical and thermal properties, rendering them highly attractive materials for thermoelectric and optoelectronic devices.

DFT insight on stability, optoelectronic, and thermoelectric features of Na3XO (X = Cu, Ag) anti‐perovskites: Promising materials for sustainable energy applications

AbstractThe structural stability, elastic, optoelectronic, and thermoelectric characteristics of anti‐perovskites Na3XO (X = Cu, Ag) have been studied using density functional theory (DFT). The computed formation energy suggests these materials' potential synthesis and thermal stability. The structural and elastic properties of Na3CuO and Na3AgO anti‐perovskite compounds were analyzed using the Perdew–Burke–Ernzerhof (GGA‐PBE) generalized gradient potential approximation. The electronic and thermoelectric properties are calculated using the TB‐mBJ approximation. The materials are identified as direct narrow band gap semiconductors with band gaps of 0.65 and 0.43 eV. The analysis of two‐dimensional charge density contours indicates that Na3CuO and Na3AgO have a mixed bonding character, as validated by the investigation of electron charge density. We analyzed the optical properties of Na3CuO and Na3AgO, including dielectric function, refractive index, absorbance, optical reflectivity, and energy loss, using photon energy up to 6 eV. The investigated thermoelectric characteristics demonstrate figure of merit (ZT) values of 0.58 and 0.56 at room temperature. Consequently, the analyzed anti‐perovskites might address waste heat management requirements and sustainable energy solutions.

Atomically substitution engineering of europium-based dichalcogenides for enhancing tailored properties and superior applications

Transition-metal chalcogenides can be used as photoconductors and in optoelectronic devices. Research on the electronic properties of KBaSbSe3 has established that the parental compound possesses an indirect band gap of 2.0 eV. By europium doping, the material’s band structure experienced a transformation, resulting in a direct semiconducting behavior. This change was observed in spin-up and spin-down polarizations, with a bandgap of 1.5 eV. An analysis of the electron charge density (ECD) contour of the (101) crystallographic plane has been conducted to examine the bonding characteristics. Based on the reflectivity spectra, it is evident that both compounds exhibit a significant level of reflectivity, making them potentially suitable for shielding against visible and UV radiation. The calculations of birefringence demonstrate the ability to achieve phase matching for both observed compounds. Calculations were performed using Boltzmann transport theory to determine the Seebeck coefficient, Hall coefficient, electrical and thermal conductivities, and figure of merit. The compound KBaSbSe3 exhibits N-type at low temperatures and P-type due to a change in the Seebeck coefficient. Both compounds have excellent optical and thermal responses, making them promising materials for optoelectronic and thermoelectric devices.

Pressure‐Induced Effects on BaPbO3: A Prospectively Valuable Material for Piezoelectric Applications via DFT

AbstractEmploying density functional theory within the Wien2k code, first‐principle calculations are conducted to explore the impact of applied pressure up to 80 GPa on the structural, mechanical, thermal, and electronic characteristics of BaPbO3. Demonstrating metallic behavior with ductile attributes, BaPbO3 exhibits a decreasing anisotropic nature under escalating pressure. Evaluation of cubic elastic constants, optimization curves, and enthalpy of formation indicates the compound's mechanical and thermodynamic stability under high pressure conditions. Calculated values of C11 and C44 reflect heightened resistance to unidirectional compression and increased stiffness under pressure. These mechanical properties position BaPbO3 as a promising candidate for diverse industrial applications across varying pressure ranges, including utilization in piezoelectric materials (0–20 GPa) and high‐pressure sensors. Additionally, charge density contours suggest a combination of ionic (Ba─Pb) and covalent bonding (Pb─O) within the compound's constituent atoms. The material can exhibit potential applications as a piezoelectric sensor at 0–20 GPa, high‐pressure actuators ≈20 GPa, and as a high melting temperature resistive substrate for laser welding and cutting materials.

Theoretical studies on phase stability, electronic, optical, mechanical and thermal properties of chalcopyrite semiconductors HgXN2 (X=Si, Ge and sn): A comprehensive DFT analysis

In this study, the ground state physical properties of Hg-based chalcopyrite semiconductors, HgXN2 (X = Si, Ge and Sn), are investigated using the density functional theory (DFT), which is based on full potential linearized augmented plane wave (FP-LAPW) method. The structural, electronic, optical, mechanical and thermal properties of the body-centered tetragonal (BTC) phase, HgXN2 (X = Si, Ge and Sn), have been calculated using the modified Becke-Johnson exchange-correlation potential (TB-mBJ). The obtained lattice parameters and volume are in good agreement with the values reported earlier, indicating that the results are reliable and reproducible. The phase stability of the titled compounds is elaborately studied and it is confirmed that all are thermodynamically, dynamically and mechanically stable. The electronic band structure demonstrated a direct band gap of 1.70 eV, 0.99 eV, and 0.94 eV for the HgXN2 (X = Si, Ge and Sn) compounds, respectively. Both HgGeN2 and HgSnN2 compounds have a notably lighter carrier effective mass, resulting in higher carrier mobility and conductivity than HgSiN2. The order of the mechanical hardness is as follows: HgSiN2> HgGeN2> HgSnN2. The studied materials are also anisotropic in mechanically and optically. All the title compounds exhibit ductile behavior. The charge density contour plots indicates the dominant covalent nature of the bonds in HgXN2 (X = Si, Ge and Sn). All these compounds have a high absorption coefficient and low optical reflectivity in the visible light range. Due to the favorable band gap and high absorption coefficient, these compounds could be suitable for optoelectronic or photovoltaic device applications. Moreover, the thermal expansion coefficient, thermal conductivity, melting point and fracture toughness behavior have been calculated, which also showed promise for thermal barrier coating (TBC) applications.

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.

Importance of surface morphology on secondary electron emission: a case study of Cu covered with carbon, carbon pairs, or graphitic-like layers

Understanding the relationship between surface adsorbates and secondary electronic emission is critical for a variety of technologies, since the secondary electrons can have deleterious effects on the operation of devices. The mitigation of such phenomena is desirable. Here, using the collective efforts of first-principles, molecular dynamics, and Monte Carlo simulations, we studied the effects of a variety of carbon adsorbates on the secondary electron emission of Cu (110). It was demonstrated that the adsorption of atomic C and C_2 pair layers can both reduce and increase the number of secondary electrons depending on the adsorbate coverage. It was shown that under electron irradiation, the C–Cu bonds can be dissociated and reformed into C_2 pairs and graphitic-like layers, in agreement with experimental observation. It was verified that the lowest secondary electron emission was due to the formation of the graphitic-like layer. To understand the physical reason for changes in number of secondary electrons for different systems from an electronic structure perspective, two-dimensional potential energy surfaces and charge density contour plots were calculated and analyzed. It was shown that the changes are strongly influenced by the Cu surface morphology and depends highly on the nature of the interactions between the surface Cu and C atoms.

Electronic structure, thermodynamics, and thermoelectric properties of YxAl1−xN semiconductor alloys for new promising optoelectronics and energy conversion: Ab Initio study

Key characteristics such as structural, electronic, thermodynamic, and thermoelectric of wurtzite yttrium aluminum nitride (YxAl1−xN) semiconductor alloys (with 0≤ x ≤ 0.375) were investigated using Ab Initio density functional simulation within powerful full-potential linear augmented plane wave (FP‒LAPW) method. The equilibrium structural parameters (a0, c0, c0/a0,V0) were determined using the revised GGA−PBEsol approach in perfect agreement with experiments. The lattice a0-parameter varies almost linearly with yttrium concentration with a bowing of −0.08597 Å, while the c0-parameter has a bowing of −0.5715 Å. The lattice dynamics of doped YxAl1−xN systems were analyzed based on formation energy and phonon frequencies. Electronic structures of wurtzite YxAl1−xN described from a modern nKTB−mBJ potential show bandgap engineering with a range of [6.10 eV–3.85 eV] for x varies from 0 to 0.375, covering emission wavelengths [203 nm–322 nm] in the ultraviolet spectrum. The electron charge density contours indicate ionic bonding in wurtzite YxAl1−xN. Using the quasi-harmonic Debye model, thermodynamic properties of YxAl1−xN alloys, including volume (V0), mass modulus (B0), specific heat (Cv), thermal expansion (α), entropy (S), Debye temperature (ΘD) and Grüneisen parameter (γ), were calculated and analyzed under temperature and pressure effects. Moreover, electronic transport properties, such as the Seebeck coefficient (S), electrical conductivity (σ/τ), power factor, thermal conductivity (κel/τ), and figure of merit (ZT), of YxAl1−xN alloys were determined using BoltzTraP code. YxAl1−xN (at x = 0.25 and T = 600 K) exhibited the largest magnitude of S, with a value of ∼213.9 μV/K, and ZT ∼ 0.72. It also had the lowest value of κ/τ ∼9.9 × 1013 W m−1.K−1.s−1. Wurtzite YxAl1−xN crystal appears to be an extremely interesting candidate for potential applications in optoelectronics (UV) and future green energy system.

Electronic and optical properties of quaternary selenides for optoelectronic applications: Insights from DFT+U‐computations

AbstractThe optical properties, electronic charge density, electronic structure of the new layered selenides materials, BaGdCuSe3, CsUCuSe3, CsZrCuSe3, and CsGdZnSe3 compounds have been calculated by using the full potential and linear augmented plane wave (FP‐LAPW) methods as applied in the WIEN2k package, which is based on the density functional theory. The ALnMSe3 compound's structure of these was (A = Cs, Ba; Ln = Zr, Gd, U; M = Cu, Zn) is composed of (n = 1, 2) layers, which might be separated by A atoms. It is to be observed that there is strong hybridization between the s, p, and d states of Zr, Gd, and Cu atoms. Around the gadolinium atom, the charge density contours are completely circular, but the Gadolinium “Gd” atom shows an ionic nature. To calculate the refractive index, we used Kramer's Kronig correlations with the imaginary part dielectric function. The decrease in the refractive index is due to the lack of probability for direct excitation of the electrons, resulting in a loss of energy. The value of the static refractive index for all reference compounds is about 1.75–2.25, which is indication that the material used in optoelectronic devices.

Adsorption behavior of diatomic gases with defected hexagonal boron nitride nanosheet: A DFT study

In this study we have carried out the interaction of homo and hetero diatomic (H2, Cl2, N2, O2, CO, NO) gases with pristine, B-vacancy (BV) and N-vacancy (NV) defected hexagonal boron nitride nano-sheet (h-BNNS). We have shown that, the interaction of the gases with pristine h–BNNS were weaker and resulted physi-sorption of gases. We have shown here that the interaction of the gases with BV and NV were stronger and it resulted either spontaneous dissociation of the gas molecules or chemi-sorption and or physi-sorption of the molecules. The adsorption energy, optimized geometry, electronic structure, density of states, charge transfer for the interaction and the charge density contour of the complex systems were studied in this report. This study will be useful for oxidative-reduction type of chemical reactions, detection of toxic gases but also removing the toxic gases from the contaminated areas.

Computational Prediction of Graphdiyne-Supported Three-Atom Single-Cluster Catalysts

Computational Prediction of Graphdiyne-Supported Three-Atom Single-Cluster Catalysts

Theoretical investigations of structural, electronic, optical and thermoelectric properties of oxide halide perovskite ACoO3 (A=Nd, Pr or La)

Perovskite oxides have emerged as promising alternatives for photovoltaic devices due to their astonishing optoelectronic properties. Nevertheless, a density functional theory study was performed on the electronic, optical, and thermoelectric properties of ACoO3 (A = Nd, Pr, and La) by TB-mBJ potentials. Based on the optimized structures, the observed results show that studied compounds display p-type semiconductor behavior with a bandgap of 1.95 eV, 1.08 eV, and 1.57 eV respectively. Hence, spherical charge density contours illustrate the ionic character of Nd/Pr/La/Co and O. The optical spectra are reported and discussed, the maximum absorption intensity for the LaCoO3 is ∼20 × 104 cm around 400 nm. Furthermore, the figure of merit, the electrical and thermal conductivity of each compound are investigated by applying Boltzmann transport theory, the high mobility of carriers enhances the Seebeck coefficient and electrical conductivity of ACoO3 (A = Nd, Pr, and La) materials. Our finding results make these materials favorable candidates for photovoltaic applications.

Effects of hydrogen/halogen –edge termination on structural, electronic, and optical properties of planar silicene nanoribbons SiNRs

The effects of (hydrogen/halogen)–edge termination on the structural, electronic, and optical properties of planar SiNRs with either zigzag (ZSiNRs) and armchair (ASiNRs) edges are investigated by means of DFT calculations . The obtained results show that X-edge termination is a new approach to tune and open the band gap in planar SiNRs, and exhibiting a metallic character. The density of states (DOS) analysis reveals a strong hybridization between halogen- p and edges Si- p states, which is not the case of H- s and edges Si- p states. The calculated charge density contours manifest the ionic nature of Si–X (X = H, F, Cl, Br, and I) bonds. However, the Si–Si bonds display a typical covalent bonding feature. The investigation of the optical properties for both polarizations indicates that 7-ASiNR-X and 5-ZSiNR-X exhibit strong optical anisotropy in infrared (IR), visible (VIS), and ultraviolet (UV) regions under both polarizations, making them promising candidates for optoelectronics and optical nanodevices such as polarization-sensitive photodetectors. Besides, for perfect planar ASiNR and ZSiNR, the strong absorbance peak of ε 2 y y ( ω ) has been found to occur at 0.32 (0.36) eV, respectively, suggesting that these compounds may be candidates for IR optoelectronic devices . The most dominant absorption peaks centred at 5.17 and 4.5 eV for ASiNR-H and ZSiNR-H systems, respectively, indicate a high absorbance in the UV range, making them prospective nanomaterials for photovoltaic devices . • The X-edge terminated planar ZSiNRs exhibit a metallic character. • Si–X (X = H, F, Cl, Br, I) bonds manifest an ionic nature whereas Si–Si bonds display a typical covalent bonding. • 7-ASiNR and 5-ZSiNR exhibit a strong optical anisotropy (IR, VIS, UV), hence promising candidates for optoelectronics. • Perfect planar ASiNR/ZSiNR exhibit a strong absorbance peak at 0.32/0.36 eV hence can be used for IR optoelectronic devices. • The high absorbance in UV range makes them prospective nanomaterials for photovoltaic devices.

Theoretical Investigation of CsBX3 (B = Pb, Sn; X = I, Br, Cl) Using Tran–Blaha Modified Becke–Johnson Approximation for Flexible Photoresponsive Memristors

AbstractThe structural, elastic, charge conduction and photoresponsive properties of halide perovskites, i.e., CsBX3 (B = Pb, Sn; X = I, Br, Cl) are investigated using the full potential‐linearized augmented plane wave (FP‐LAPW) method in the frame work of density functional theory (DFT). Perdew Burke Ernzerhof (PBE) functional belonging to the generalized‐gradient approximation (GGA) is implemented. For the better estimation of electronic parameters, the Tran–Blaha modified Becke–Johnson (TB‐mBJ) potential is employed. The elastic parameters such as bulk modulus, shear modulus, Young's modulus, the Pugh's ratio, anisotropy factor, Poisson's coefficient, and melting temperature (Tm) are estimated within Voigt‐Ruess‐Hill approximations. The energy band structure results, total density of states (TDOS), partial density of states (PDOS) outcomes, and isosurface charge density contour plots disclose that Sn2+and I1− are more appropriate divalent cation and anion respectively, among all studied composites especially for the application of photoresponsive resistive random access memory (RRAM) devices. Moreover, partial density of states (PDOS) outcomes depict that conduction band formation is consequence of hybridization of electrons from p‐orbitals of divalent cations, i.e., Pb, Sn and I/Br/Cl halogen anions. Besides, regarding charge conduction Sn‐based composites offer minimal energy bandgap as compared to Pb‐based composites. The energy bandgap order for Sn‐based compounds is found as CsSnI3> CsSnBr3> CsSnCl3. The optical analysis renders that CsSnI3 have the capability to absorb a wide range of ultraviolet (UV), visible and infrared (IR) electromagnetic incident radiations thus, make it much suitable material for optoelectronic memristors and associated applications.

Unveiling the interaction profile of cisplatin with gold-supported magnesia film

As far as we know, the adsorption behavior of coordination complex on metal-supported oxide film has never been systematically investigated before, which obstructs the rational design and functional application of inverse composite catalyst toward chemisorbing substances with coordination bonds. In clinical practice and experiments, magnesia has been used together with cisplatin for intravenous magnesium supplementation, to reduce the side effects of cisplatin. In this contribution, interaction profile between cisplatin anticancer drug with magnesia and gold-supported magnesia is elucidated for the first time utilizing periodic density functional theory (DFT) calculations with dispersion corrections. Equilibrium geometries, translation potential profile, differential charge density contour, particular occupied orbitals, projected density of states and electron localization function are characterized to reveal the structural features and electronic properties of cisplatin chemisorption on magnesia-gold hybrid structure. It is anticipated that the interaction mechanism of cisplatin with inert and nontoxic magnesia film could provide useful clue for novel application of oxide-metal composite constructed by depositing oxide film on metallic slab toward chemisorbing and treating coordination compounds.

Structural, thermo-elastic, electro-magnetic and thermoelectric attributes of quaternary CoNbMnX (X = Al, Si) Heusler alloys

This investigation consists of performing the structural, thermodynamic, electronic, magnetic and thermoelectric characteristics of the quaternary Heusler CoNbMnX (X = Al, Si) alloys using DFT within Wien2k code. Our calculations show that the atomic arrangement of the two alloys CoNbMnAl and CoNbMnSi is Type-I. From the elastic constant and the formation energy values, these compounds are predicted to be mechanically and thermodynamically stable, thus can be formed experimentally. The calculated values of their bulk modulus and cohesive energy values show that CoNbMnSi is more rigid than CoNbMnAl. From the analysis of the electronic properties, CoNbMnAl is identified to be paramagnetic and semiconductor alloy with 0.15 eV narrow indirect (Γ-X) band gap. Whereas, CoNbMnSi is characterized as a ferromagnetic alloy with half-metallicity character having a total magnetic moment of 1μB. The charge density contours and Fermi surface, predict a combined covalent and ionic bond between the atoms of CoNbMnX alloys. The calculated thermoelectric parameters assume that these alloys tend to behave as p-type with the same thermoelectric efficiency for either charge carriers; hole or electron. Depending on the high Seebeck coefficient value and ZT = 1 of the present alloys, potential applications are predicted, such as spin injection materials and spintronic applications.

Influence of alloying elements on mechanical and electronic properties of NbMoTaWX (X = Cr, Zr, V, Hf and Re) refractory high entropy alloys

NbMoTaW refractory high entropy alloy (RHEA) has shown great potential applications for high temperature components due to its high temperature mechanical strength. However, the brittleness at room temperature hinders its engineering application and further development. To overcome this deficiency, refractory alloying elements with melting temperatures over 1850 °C, i.e., Cr, Zr, V, Hf, and Re, were chosen to enhance the mechanical performance of NbMoTaW RHEA in the present work. The effects of refractory alloying elements on the strength and ductility of NbMoTaW RHEA were investigated via a combination of theory and experiment. To be specific, the first-principle calculations based on density functional theory were employed to predict the mechanical properties of the alloyed NbMoTaWX (X = Cr, Zr, V, Hf and Re) RHEAs and explain the alloying effect from the atomic and electronic level. Moreover, the phase structures of the alloyed RHEAs were determined based on the formation enthalpy and cohesive energy, as well as some empirical parameters, such as the average valence electron concentration VEC and atomic size difference δ. In combination with the experimental results, the calculated elastic constants and modulus indicated that most of these alloying elements enhanced the strength of NbMoTaW RHEA, while only Zr-alloying significantly improved the ductility. The strengthening mechanism of different elements was well analyzed based on the total and partial density of states, overlapping Mulliken population, charge density contour, and atomic distance. The improvement of the ductility for Zr-alloying was attributed to the formation of Zr–Zr metallic bonds in the alloyed NbMoTaWX RHEAs. The theoretic predictions were confirmed by the experimental investigations. The present work provides a good guidance for design and construction of NbMoTaW RHEA.

Strain induced structural transformation, mechanical and phonon stability in silicene derived 2D-SiB

Two-dimensional monolayer SiB is a silicene derivative exhibiting buckling of atoms similar to that seen in silicene. This manuscript presents a systematic study of the strain-dependent variation of the structural, mechanical, and dynamical properties of SiB. Strain was applied in the uniaxial armchair, uniaxial zigzag, and biaxial directions within the range of −0.2 to 0.3. The resultant strain energy plot indicates anisotropic behavior of SiB in these directions. The SiB showed a mechanical strength that was higher than its counterpart, silicene, by an order of 30%. The elastic constant data from the undeformed SiB indicated an anisotropic nature, which was also seen with all the strain directions. Charge density contours, along with Bader charge analysis, confirmed the ionic nature of SiB in its original form. This nature became covalent as the strain varied from the compressive to the tensile regime in the uniaxial zigzag and biaxial directions. The major finding described in this manuscript is a new flat conformation having orthorhombic symmetry in contrast to the buckled structure. In addition, this material was observed to attain stability with the application of uniaxial tensile armchair and zigzag directional strains. Ab-initio molecular dynamics simulation confirmed the thermal stability of SiB in its new conformation.

Insights into the Impact of Yttrium Doping at the Ba and Ti Sites of BaTiO3 on the Electronic Structures and Optical Properties: A First-Principles Study.

We reported a systematic study of the effects of Y doping BaTiO3 at Ba and Ti sites. We assessed the structural, electronic, and optical properties by employing first-principles calculations within the Tran–Blaha-modified Becke–Johnson (TB–mBJ) potential and generalized gradient approximation + U approaches. We calculated the lattice constants and bond lengths for pure and Y-doped BaTiO3. We explored the consequences of electronic structure and optical property modification because of Y doping in BaTiO3. Indeed, Y doping has led to various modifications in the electronic structures of BaTiO3 by inducing a shift of the conduction band through lower energies for the Ba site and higher energies for the Ti site. It was found that Y doping, either at Ba or at Ti sites, strongly enhanced the BaTiO3 dielectric constant properties. The transformation in bonding was explored via the charge density contours and Born effective charges. We used the state of art of polarization theory based on finite difference and Berry-phase approaches to investigate piezoelectricity. Y doping has increased the dielectric constants but canceled the piezoelectricity as they changed to metallic nature. We could look into the future for potential doping, preserving the semiconductor nature of BaTiO3 and increasing the permittivity with large dielectric loss.

Probing the structural, electronic, mechanical strength and optical properties of tantalum-based oxide perovskites ATaO3 (A = Rb, Fr) for optoelectronic applications: First-principles investigations

In the present manuscript, structural, optoelectronic and mechanical properties of perovskite oxides ATaO3 (A = alkali metals = Rb, Fr) have been investigated using first principles study based on density functional theory (DFT). These calculations involve full potential linearly augmented plane wave (FP-LAPW) technique along with Perdew-Burke-Ernzerhof–generalized gradient approximation (PBE-GGA) and PBEsol exchange potentials within the framework of WIEN2K code. In addition, PBE plus Tran and Blaha modified Becke-Johnson (PBE + TB-mBJ) functional have been utilized to improve the electronic properties. These compounds belong to the semiconductor category, which include contributions of Rb-d, Fr-d/f, Ta-d and O-2p orbitals to explore their behavior. Spherical charge density contours illustrate ionic character of Rb and Fr, while significant sharing of the elliptical isolines indicates covalent character between Ta and O. Three independent elastic constants endorse mechanical stability of the studied systems, which also confirm their brittle nature. Because of poor reflectivity, good optical conductivity and absorptivity of incident energetic photons make these materials as potential candidates for wide range of applications, particularly, in optoelectronic like devices.