Electronic Properties Research Articles

Investigation of superconductivity of A15 type cubic Nb3Os material by using density functional theory

In this study, the structural, elastic, electronic, phonon and electron-phonon interaction properties of A15 type cubic Nb3Os compound were investigated by density functional theory. The lattice constant of this compound was obtained in agreement with experiments, and the investigation of elastic properties revealed its ductile nature. From electronic calculations for Nb3Os, the density of states at Fermi level (N(EF)) was found to be 5.31 states/eV with the largest contribution of Nb 4d orbitals. According to the results obtained from phonon calculations, Nb3Os was found to be dynamically stable in the cubic A15 structure and phonon modes were largely formed by the vibrations of Nb atoms. Using the electronic and phonon properties, we determined the Eliashberg spectral function, which illustrates the electron-phonon interaction. The electron-phonon interaction parameter and average phonon frequency values for Nb3Os were found to be 0.41 and 222.97 K, respectively. The calculated superconducting transition temperature of 1.05 K is in excellent agreement with the experimental value of 1.02 K.

Effects of oxygen vacancies on the structural, electronic, and optical properties of the photocatalytic InTaO4 compound

We conducted first-principles calculations based on density functional theory to investigate the impact of the oxygen vacancies on the structural, electronic, and optical properties of the InTaO4 compound. The latter is a famous photocatalytic semiconductor with its optical absorption in the visible range being an object of controversial interpretations. The presence of two types of isolated oxygen vacancies, O1 and O2, occupying 4g(1) and 4g(2) Wyckoff positions respectively, has been simulated within the frame of the supercell approach. Electronic structure and optical absorption (OA) have been calculated using the Becke-Johnson exchange-correlation potential. It is found that the presence of both types of vacancies generates defect states (DS) inside the band gap, primarily involving In-6s and O-2p states. The calculated valence-to-conduction-band band gap (4.25 eV) and DS-to-conduction-band band gap (2.5 eV) closely align with the experimentally determined OA edges for two onsets of InTaO4 absorption. The analysis of the calculated OA spectra leads to the conclusion that only O1 vacancy-induced absorption is consistent with the experimental OA, while O2 vacancy-induced absorption appears absent. This discrepancy probably arises from a higher concentration of O1 vacancies formed during crystal growth, attributed to the fact that the calculated defect formation energy of O1 vacancy is 0.258 eV lower compared to O2 vacancy. Consequently, the photocatalytic activity of InTaO4 is ascribed to intrinsic defects, primarily O1-type vacancies, though the influence of other defects cannot be entirely ruled out.

Exploring electronic characteristics of bilayer HfS2 under mechanical strain and external electric field: a first-principles approach

This study employed the density functional theory (DFT) to explore the dynamic stability of different stacking configurations of bilayer HfS2 (2L-HfS2) and the influence of external conditions on its electronic properties. These results indicate that the AA configuration is the most stable among the various stacking configurations. Calculations of the carrier effective mass revealed that the artificially stacked 2L-HfS2 maintained a small effective mass of electrons and holes and exhibited high carrier mobility. Further investigation revealed diverse trends in the electronic properties of 2L-HfS2 under vertical strain, in-plane strain, shear strain, and an applied external electric field. These variations encompass bandgap size alterations, band structure evolution, and transitions in the metallic behavior. This systematic study elucidates the regulatory effects of different strains and external electric field conditions on the electronic properties of 2L-HfS2, thereby providing a vital theoretical foundation and experimental guidance for its application in electronics and optoelectronics.

Synergistic Effect of CexOy and Zn ion within the ZIF-zni Framework for Enhanced Electrocatalytic Reduction of CO2

In recent years, human activities have led to an unprecedented rise in atmospheric CO2 levels, causing significant environmental challenges. To combat this issue, there’s growing interest in the conversion of CO2 into valuable chemicals. This study reports the synthesis and electrocatalytic evaluation of CexOy/ZIF-zni catalysts for CO2 reduction. The catalyst exhibited remarkable selectivity to CO, achieving excellent Faradaic efficiency (FE) of 87.7% at an overpotential of 170mV. The findings revealed that by adjusting the applied potential during electrolysis, it was possible to tune the catalyst's electronic properties. This resulted in a reduced overpotential and a lower CO onset potential of -300 mV. Density functional theory (DFT) calculations revealed that the synergistic interaction between the oxygen of CexOy and the Zn ion of the ZIF-zni, exposes cerium as the active site for CO2 activation. This interaction also stabilizes the crucial *COOH intermediate, facilitating the electrochemical CO2 reduction reaction.

Tailoring the physical, optoelectronic and transport properties of novel lead-free Sodium perovskites Na2TeX6 (X = Cl, Br, I) using DFT computation for photovoltaic and thermal devices

In this work, we analyzed the system, elastic, electronics, optical, as well as thermoelectric properties of perovskites Na2TeX6 (X = Cl, Br, I) systems using a potential linearization augmented plane Wave method with the help of WIEN2k. code. The tolerance factor, fermi energy, and mechanical characteristics define the stability of perovskites Na2TeX6 (X = Cl, Br, I) systems. The electronic properties were calculated using the generalized gradient plus the modified Becke-Johnson method. The computed values of the compounds Na2TeX6 (X = Cl, Br, I) are 3.15 eV, 2.54 eV, and 1.85 eV, indicating that the analyzed materials have electronic material. We determined the optical characteristics based on the facts and hypotheses of the dielectric function, refractive index, reflection, and absorption coefficients, taking into consideration the usage in photovoltaic and optoelectronic devices. Investigation of their transport characteristics reveals that both materials have been thermodynamically stable. The compounds were predicted in the temperature range of 200-1200 K for electrical properties such as electrical conductance, Seebeck coefficient, thermal conductivity, and power factor. At low temperatures, the compounds had a good Seebeck coefficient, which shows that the hole is the main part of the system and the solids nature is p-type. The perovskites to Na2TeX6 (X = Cl, Br, I) compound's high zT values suggested that they may be employed in thermoelectric devices.

DFT Study of Nanotubes as the Drug Delivery Vehicles for an Anticancer Drug

Abstract: Chemicals and poisons in the body interfere with the cell cycle and inhibit the growth of cancer cells. In this way, the function of chemicals in the body is controlled by taking anti-cancer drugs. Due to the degradability and compatibility of carbon nanotubes and boron nitride with the environment, they can act as suitable drug carriers for the transfer of anticancer drugs and deliver the drugs to the target cells. In the current work, the encapsulation of Formestane (FMS) anticancer drug into the carbon (CNT) and boron nitride (BNNT) (8,8) nanotubes was investigated for the first time using the density functional theory: B3LYP/3-21G* and the natural bond orbital analysis in the gas phase. Using natural bond orbital analysis, the charge transfer between FMS drug and CNT and BNNT nanotubes (8,8)/ FMS (BNNT/FMS) complexes were explored. Based on the results obtained from the calculation of encapsulation energy, it was found that the adsorption process was favorable. The interaction effects of FMS drug and CNT and BNNT (8,8) nanotubes on the natural bond orbital charge, the chemical shift parameters, and electronic properties were also evaluated. This study revealed that CNT and BNNT (8,8) nanotubes can be a suitable carrier for FMS drug delivery. The ultraviolet-visible spectra of the FMS drug, the CNT and BNNT (8,8), and the BNNT/FMS complexes were computed using time-dependent density functional theory (DFT: B3LYP) calculations.

Biaxial strain effects on electronic, transport, and thermoelectric properties of SnX[formula omitted] (X = Se, Te) and Janus SnSeTe 1T-monolayers

Biaxial strain in two-dimensional materials plays a crucial role in degenerating the valence and conduction bands, leading to energy dispersion in the band structure and causing changes in transport properties, such as carrier mobility, Seebeck coefficient, and electrical conductivity. Herein, we investigated the effects of biaxial strain on SnX2 (X = Se, Te) and the Janus SnSeTe 1T-monolayer using density functional theory, deformation potential, and semiclassical Boltzmann transport theory. Our findings reveal that the studied 1T-monolayers exhibit high and directionally isotropic electron mobility. Biaxial tensile strain has the effect of increasing the bandgap, predominantly reducing the effective mass of electrons while increasing that of holes. This results in an enhanced electron mobility along with a simultaneous reduction or increase in the concentration of electron carriers or holes, respectively. Especifically, in the case of the Janus SnSeTe 1T-monolayer, we observed a remarkable 68% increase in electron mobility, reaching a value of 1588 cm2V−1s−1. This increase contributes to higher thermoelectric performance due to elevated electrical conductivity and a simultaneous rise in the Seebeck coefficient when subjected to biaxial strain. Our study underscores that strain engineering is an effective strategy for achieving improved thermoelectric properties, particularly exemplified by the SnSeTe 1T-monolayer, which achieved a maximum value of 2.25 for n-type due the ultralow thermal conductivity of 0.359 Wm−1K−1 as result of strong phonon anharmonicity on acustical and optical modes.

Investigation of electronic, elastic, dynamical, thermodynamic and thermoelectric properties of Cobalt based half-Heusler compounds

Heusler compounds have attracted remarkable attention from scientists over the year by virtue of their peculiarity and suitability in multi-functional applications. In the current study, the structural, elastic, dynamical, thermodynamic and thermoelectric properties of CoMSb (M = V, Nb and Ta) half-Heusler compounds were computed. Projector augmented-wave (PAW) pseudopotentials with PBE exchange correlation functional have been used to obtain the results for the studied compounds. The computed elastic constants satisfy the general stability condition based on the cubic symmetry and endorse the ductile nature of the compounds. The CoVSb compound is predicted to be ferromagnetic half-metallic compound while CoNbSb and CoTaSb are non-magnetic compounds. The dynamical properties revealed the dynamical stability in CoVSb and CoTaSb compounds while the imaginary frequency observed at W⟶L⟶Γ predicts instability in CoNbSb compound. The thermodynamic properties for the compounds were reported. The thermoelectric properties were calculated based on the results obtained from electronic structure using semi-classical Boltzmann theory. The ductile nature and the figure of merit computed predict CoMSb (M = V, Nb and Ta) are relatively good for thermoelectric application.

Restoring the electronic properties of epitaxial graphene on SiC substrate by Ar intercalation

Thermal decomposition of 6H-SiC(0001) under an argon atmosphere is a promising technique to fabricate large-scale epitaxial graphene monolayers for electronic applications. In this manuscript, we report on the intercalation of argon, hydrogen and oxygen atoms underneath a graphene buffer layer (BL) on SiC(0001), involving bond formation between the intercalated agent and Si atoms. Density Functional Theory calculations were performed to investigate the atomic structure, stability and electronic properties of quasi free-standing monolayer graphene and bilayer graphene, accomplished by intercalation. According to our results, as the Ar intercalated atoms saturate the silicon dangling bonds in the upper SiC surface, the BL is completely detached from the substrate and transformed into free-standing graphene. Ar intercalation would be hindered by the concurrent and thermodynamically more spontaneous adsorption of Ar atop the graphene layers, resulting in a pronounced decrease of the process efficiency. High Ar-coverage regimes and low kinetic barriers for Ar intercalation might shift the intercalation/adsorption balance. These factors as well as strategies such as ion implantation could be explored to identify more favorable conditions to experimentally test Ar intercalation as a simple method to achieve control of the electronic properties of the BL and help preserve the unique characteristics of graphene.

Zigzag boron nitride nanotube functionalization as a sensor for the recognition of group IIA (Mg2+, Ca2+) metal ions, quasi-metal (Si2+, Ge2+) ions, and transition metal (Cu2+, Zn2+) ions: a computational study.

Boron nitride nanotubes (BNNTs) provide an exceptional and sophisticated platform for detecting metal ions with high surface area and remarkable chemical stability. Metal cations tend to bind to the surface of BNNTs, which leads to significant changes in the electrical properties of nanotubes. BNNT-based metal ion sensors have shown promising results in various applications, including water quality monitoring, biomedical research, industrial quality control, and environmental monitoring. In the present study, we have explored the electronic sensitivity of the BNNT to metal ions (Si2+, Ge2+, Cu2+, Zn2+, Mg2+, and Ca2+). The interaction between the ions with the pristine BNNT is performed in the solution phase. The results show that ion adsorption on the nanotube surface is exothermic and favorable. The density of states calculation is presented to investigate the electronic properties of the nanotube during the adsorption process. The results display that an increase in the electrical conductivity of the complexes accompanies the reduction in the energy gap. Based on the obtained data, the Si2+ and Ge2+ cations adsorbed on the BNNT with satisfactory Eg changes (%ΔE) can be promising candidates for better sensing ability. All calculations are conducted within the density functional theory (DFT) using the ωB97XD functional and 6-31G(d,p) basis set. The present approach incorporates the utilization of empirical atom-atom dispersion in conjunction with long-range correction. The calculations are performed using the quantum chemistry package GAMESS, and the obtained results are visualized by employing the GaussView 6.0.16 program.

Influence of Pressure on Structural, Electronic, Optical, and Elastic Properties of Lead-Free Chalcogen Perovskite LaLuS3 via First-Principles Calculations: Implications for Optoelectronic Applications

Abstract Chalcogen perovskites have garnered increasing attention as promising materials for optoelectronic applications. In this study, we employed the first-principles method to investigate the structural, electronic, optical, and elastic properties of LaLuS3 under hydrostatic pressure at various levels. Through a thorough analysis of the calculated electronic structures, we observed that LaLuS3 exhibits direct band gaps, with the magnitudes of these gaps changing as the pressure varied. Specifically, the band gaps decrease by 2.19 eV, 2.025 eV, 1.365 eV, and 0.6043 eV at hydrostatic pressures of 0%, 10%, 20%, and 30% GPa, respectively. Furthermore, we observed shifts in the conduction band minimum and valence band maximum positions, indicating the potential of LaLuS3 for perovskite-based devices. This suggests that external pressure can serve as a powerful tool for designing new functional materials with intriguing properties. Our investigation also revealed promising optical properties of LaLuS3 under high pressures, further affirming its potential for optoelectronic and solar cell applications. The optical functions of the material are enhanced with increasing pressure, particularly in the ultraviolet range, highlighting its suitability for a wide range of optoelectronic devices. Moreover, while maintaining mechanical stability, hydrostatic pressure exerts a significant influence on the mechanical properties of LaLuS3. Lastly, our calculations on anisotropy demonstrate that applied pressure can enhance the anisotropic nature of LaLuS3. This comprehensive study underscores the efficacy of hydrostatic pressure as a systematic approach to modifying the photovoltaic performance of halide perovskites.

Energy band engineering in GaS/InS and GaSe/InS van der Waals bilayers by interlayer stacking design and applied vertical electric field - An ab-initio theoretical calculation based approach

In this work, for the first time, an extensive theoretical investigation of the structural and electronic properties of the van der Waals (vdW) bilayer heterostructures of two-dimensional (2D) Gallium Sulphide (GaS)/Indium Sulphide (InS) and Gallium Selenide (GaSe)/Indium Sulphide (InS), is performed using density functional theory calculation. In this context, the effects of natural and artificial interlayer stacking configurations, and externally applied out-of-plane direction electric field are emphasized. The structural, thermal, and dynamic stabilities of individual bilayers are assessed from the cohesive energy/interlayer interaction energy, phonon spectrum, and molecular dynamics evolution, respectively. The effects of the vdW bilayer environment on the in-plane structural parameters like lattice vector, bond length, and bond angle of the constituent monolayers are comprehensively investigated. The electronic properties are estimated from the band edge energy, the density of states, energy bandgap, and interlayer energy band alignment, which are systematically analysed from the interlayer interactions in terms of interlayer distance, out-of-plane charge distribution, and interlayer charge transfer. The key findings demonstrate that the interlayer stacking engineering and applied out-of-plane electric field can induce unique and tailor-made modulations in the overall electronic properties of GaS/InS and GaSe/InS bilayer, which can be exploited in favour of electronic/optoelectronic applications.

Flexible Nanofiber Pressure Sensors with Hydrophobic Properties for Wearable Electronics

In recent years, flexible pressure sensors have received considerable attention for their potential applications in health monitoring and human–machine interfaces. However, the development of flexible pressure sensors with excellent sensitivity performance and a variety of advantageous characteristics remains a significant challenge. In this paper, a high-performance flexible piezoresistive pressure sensor, BC/ZnO, is developed with a sensitive element consisting of bacterial cellulose (BC) nanofibrous aerogel modified by ZnO nanorods. The BC/ZnO pressure sensor exhibits excellent mechanical and hydrophobic properties, as well as a high sensitivity of −15.93 kPa−1 and a wide range of detection pressure (0.3–20 kPa), fast response (300 ms), and good cyclic durability (>1000). Furthermore, the sensor exhibits excellent sensing performance in real-time monitoring of a wide range of human behaviors, including mass movements and subtle physiological signals.

Pressure effects on the structural, electronic, elastic, optical, and vibrational properties of YMg intermetallic compounds: a first-principles study

The properties of YMg in B2 structure have been comprehensively analysed using the first-principles plane-wave pseudopotential method. Specifically, the structural, electronic, elastic, vibrational, and optical properties were investigated using the generalized gradient approximation (GGA) method in the context of density functional theory. The Vienna ab initio simulation package (VASP) was utilized for these calculations. The computed lattice parameter (3.803 Å) and bulk modulus (41.33 GPa) are consistent with the earlier data on ambient pressure. The electronic band structure and energy-dependent density of states reveal the metallic nature of the titled compounds. The Born stability requirements confirmed the mechanical stability. The analysis of Pugh’s and Poisson’s ratios and Cauchy’s pressure reveals that YMg is ductile under the pressures in consideration. According to several anisotropy indices, the compound is noticeably anisotropic both in ambient and under pressure. Our investigation includes an analysis of several fundamental mechanical parameters of the material, including the bulk modulus, the pressure derivative of the Zener anisotropy factor, Poisson’s ratio, isotropic shear modulus and Young’s modulus with a particular focus on their dependence on pressure. We have determined that the elastic constants obtained remain mechanically stable, satisfying the Born Stability conditions even at high pressures of up to 60 GPa. To explore the dynamic stability of YMg, we analysed the material’s phonon dispersion curves. The examined compound displays stability under dynamic conditions from 0 GPa to 30 GPa, as evidenced by its positive vibration frequencies. However, this stability is not sustained under higher pressure, as the compound becomes unstable after 30 GPa to 70 GPa. The electronic band structure and density of states diagrams demonstrate YMg’s metallic properties. At atmospheric pressure (0 GPa), the total density of states (TDOS) near the Fermi level is approximately 1.63 states/eV, with pressure application reducing DOS. The dielectric function, refractive index, and energy loss spectra are examined within the 0–20 eV energy range. YMg exhibits its highest absorption between 4 and 11 eV. The peak optical conductivity is observed around 0.78 eV (equivalent to 1589.5409 nm), while the most significant energy loss occurs at 11.90 eV, roughly corresponding to 2.8 Hz in the ultraviolet spectrum. Moreover, we extensively analyzed the material’s phonon thermodynamic and optical properties, providing insights into its behavior under various conditions. The outcomes acquired at zero pressure are generally coherent with the current theoretical values.

Strain-induced electronic, optical and thermoelectric properties of SiC-CrX2(X = S, Se) heterostructures

Strain-induced electronic, optical and thermoelectric properties of SiC-CrX2(X = S, Se) heterostructures

Computational and experimental investigations on structural, electronic and optical properties of scheelite compounds

Abstract Oxide of tungstate has consistently been pursued for use in optoelectronic applications. This study details the synthesis of AWO4 (A=Ba, Sr and Ca) using a high-temperature solid-state method. Additionally, theoretical calculations highlight its electronic structure, density of states, photoelectric properties, and vibrational modes. The X-ray diffraction of AWO4 (A=Ba, Sr and Ca) was meticulously introduced by the utilization of Rietveld for refinement. The refined lattice parameters substantially verified AWO4 (A=Ba, Sr and Ca) as a tetragonal system of scheelite with the spatial group of I41/a, and demonstrated significant alteration with the discrepancy in the radius of alkaline earth metal (A-site) ions. The electronic configuration and optical attributes of AWO4 (A=Ba, Sr and Ca) possessing scheelite-like structure were explored using density functional theory (DFT) based computational techniques. The theoretical blueprint was derived by optimizing the structure based on defects. The postulated optical bandgap energy confirms the occurrence of direct electronic transitions at Brillouin region G points. Calculations suggested the direct band gaps of BaWO4, SrWO4, and CaWO4 at 4.385, 3.123 and 3.813 eV. This was attributed to the energy levels produced by O and A-site atoms in the valence band, and W and O atoms in the conduction band. An examination of the polarization effect and uneven electronic charge distribution between [CaO8]6- and [WO4]2- clusters brought about by structural defects in AWO4 (A=Ba, Sr and Ca) was performed. Moreover, advanced investigations have been conducted on the elastic constants and mechanical durability of AWO4 (A=Ba, Sr and Ca). This research extensively calculated the elastic moduli of various matrices utilizing DFT. The critical Pugh's ratio value was found to be>1.75, it indicated that AWO4 (A=Ba, Sr and Ca) has significant potential as a resilient material.

Electron Localization and Mobility in Monolayer Fullerene Networks.

The novel 2D quasi-hexagonal phase of covalently bonded fullerene molecules (qHP C60), the so-called graphullerene, has displayed far superior electron mobilities, if compared to the parent van der Waals three-dimensional crystal (vdW C60). Herein, we present a comparative study of the electronic properties of vdW and qHP C60 using state-of-the-art electronic-structure calculations and a full quantum-mechanical treatment of electron transfer. We show that both materials entail polaronic localization of electrons with similar binding energies (≈0.1 eV) and, therefore, they share the same charge transport via polaron hopping. In fact, we quantitatively reproduce the sizable increment of the electron mobility measured for qHP C60 and identify its origin in the increased electronic coupling between C60 units.

Isolation and Reactivity of Silepins with a Sterically Demanding Silyl Ligand

Silacycloheptatriene (silepin) species are novel silicon compounds reported in recent years. The interplay between the “closed” silepin and the “open” silylene form enables an enhanced stability of the low valent species while maintaining a high reactivity towards small molecules. In this work, two new silepins of similar structures to literature known compounds bearing modified silyl ligands are reported. A unique intramolecular activation of an aromatic hydrogen is found, and the respective formed hydrosilanes are characterized. We further synthesized iron(0) carbonyl complexes of known and new silepins in order to investigate their electronic properties relative to each other to gain more insight into substitution effect in such compounds.

Simulation of Electronic Properties, Enthalpy of Formation, and Dielectric Characteristics of Yb-Doped Single Crystal TlInS2

Simulation of Electronic Properties, Enthalpy of Formation, and Dielectric Characteristics of Yb-Doped Single Crystal TlInS2

First‐Principles Investigations of Structural, Electronic, and Elastic Properties of ZrSiO3 Perovskite: Layer Dependence, Surface Termination, and Pressure Effects

Zirconium silicate (ZrSiO3) perovskite is a promising material for various technological applications. The structural, electronic, and thermodynamic properties of ZrSiO3 perovskite are studied under different conditions, including pressure and layer configuration variations using density functional theory. The present investigation includes a thorough analysis of 2D perovskite derivatives derived from its basic 3D structure. The bulk and surface‐terminated silicon‐dominant SiO2 and zirconium‐dominant ZrO compounds are found to be mechanically stable with an anisotropy factor above 1. The calculated indirect‐bandgap values for the ZrO termination and SiO2 termination are found to be 2.585 and 1.639 eV, respectively. Moreover, the pore size of the SiO2‐terminated slab model of ZrSiO3 is calculated to be 105.39 μm and that for ZrO‐termination to be 129.30 μm. Thus, the material considered for the study can have potential applications in bone regeneration and tissue engineering. Further, the possibilities for modifying ZrSiO3 for uses in electrical devices, sensors, sustainable energy materials, and even biomedical applications like tissue engineering are intriguingly expanded by the present findings.