Band Structure Calculations Research Articles

Full band-structure calculation of semiconducting materials on a noisy quantum processor

Full band-structure calculation of semiconducting materials on a noisy quantum processor

OPTICAL PROPERTIES OF THE AgBiP2Se6 SINGLE CRYSTAL

The AgBiP2Se6 compound has emerged as one of the most studied hexachalcohypodiphosphates in recent years. This is interest is driven by its distinctive layered structure, which implies the possibility of obtaining monolayers and the observation of various of quantum effects. Most studies to date, however, have focused on first-principles calculations, while experimental investigations have primarily been limited to structural analysis and stoichiometric composition determination. This work partially addresses the gap in research by exploring the optical properties of AgBiP2Se6. Transmission spectra within the optical range of 220-1400 nm, as well as Raman spectra, were obtained from single crystalline AgBiP2Se6 samples. The band gap, determined from the transmission spectra using the graphical Tauc method, was found to be 1.44 eV. This value aligns closely with the DFT band-structure calculations using the Perdue-Burke-Erzenhorf (PBE) model without a Hubbard correction parameter (1.384 eV). The Raman spectrum of the AgBiP2Se6 crystal reveals five distinct peaks at approximately 68, 125, 169, 436, and 462 cm-1. The peak at 68 cm-1 can be attributed to the vibrational mode of the cationic centers; the peaks at 125 and 169 cm-1 can correspond to deformations within the Se-P-P and Se-P-Se bonding systems involving changes in bond angles; and the peaks at 436 and 462 cm-1 reflect bond length changes within the anionic (P2Se6)4-group.

A First‐Principles Study of Structural, Elastic, Mechanical, Thermodynamic, and Electronic Properties of Rb2XIO6 (X = Ga, In) Double Perovskites

Double perovskites (DPs) have gained the interest of researchers due to their unique properties. In present work, structural, mechanical, electronic, and thermodynamic properties of Rb2XIO6 (X = Ga, In) DPs are investigated using first‐principles calculations. The tolerance and octahedral factors are calculated in the allowed range of DPs. The phonons dispersion curves were computed with positive frequencies. The elastic constants prove the mechanical stability. Mechanical properties explore the anisotropic, brittle, and stiffer nature of both DPs. The computed band structures discover the metallic nature, where O–p and I–s states are found to cross the Fermi level. Debye temperature for Rb2GaIO6 is calculated higher than Rb2InIO6. Grüneisen parameter is evaluated to decrease with increasing pressure and temperature. Specific heat capacity is observed to saturate at 450 K. The coefficient of thermal expansion are calculated as 9 10−5 and 8.95 10−5 K−1 at 1000 K for Rb2GaIO6 and Rb2InIO6, respectively.

First-principles pressure-dependent investigation of the physical and superconducting properties of ThCr 2 Si 2 -type superconductors SrPd 2 X 2 (X = P, As)

The physical and superconducting characteristics of SrPd 2 P 2 and SrPd 2 As 2 compounds with applied pressure were calculated using density functional theory. The pressure effect on the structural properties of these compounds was investigated. The results show that both lattice constants and volume decrease almost linearly with increasing pressure. The elastic constants ( C ij ) for both compounds increase with increasing pressure and satisfy Born criteria for mechanical stability. The elastic parameters indicate the ductile behaviour and anisotropic nature of these compounds under applied pressure. The Debye temperature ( ϴ D ) and melting temperature ( T m ) increase with increasing pressure. The electronic band structure calculation of both compounds exhibits metallic characteristics at different pressures. The density of electronic states at the Fermi level, N ( E F ), consistently decreases as pressure increases, which is also reflected in the repulsive Coulomb pseudopotential ( µ* ), and the electron–phonon coupling constant ( λ ). These optical features suggest that both compounds are suitable for optoelectronic device applications. Furthermore, the superconducting transition temperature, T c , for both compounds is predicted to vary with applied pressure due to changes in ϴ D , N ( E F ) , µ* and λ .

Comparative analysis of electronic and thermoelectric properties of strained and unstrained IrX3 (X = P, As) skutterudite materials

Abstract The electronic and thermoelectric properties of unfilled IrP3 and IrAs3 skutterudites materials under hydrostatic pressures are investigated using density functional theory (DFT) combined with semi-classical Boltzmann transport theory. Calculations of the elastic properties and phonon frequencies for both strained and unstrained materials demonstrate that they are mechanically and dynamically stable, with ductility varying based on the applied pressure. For pressures ranging from 0 to 30 GPa, the band structure calculations with the GGA+TB-mBJ approximation reveal that the band gap varies from 0.400 to 0.144 eV for IrP3 and from 0.341 to 0.515 eV for IrAs3. At 0 GPa, IrAs3 exhibits a direct band gap, whereas IrP3 has an indirect band gap. As pressure increases, IrAs3 undergoes a transition from a direct to an indirect band gap above 10 GPa, while IrP3 maintains its indirect band gap characteristic throughout the pressure range. 
The thermoelectric properties, at various pressures and temperatures between 300 and 1200 K, are also computed. These properties include the Seebeck coefficient, electrical conductivity, thermal conductivity (both electronic and lattice contributions), and relaxation time. The ideal conditions for efficient thermoelectric properties in IrAs3 are achieved at 30 GPa and 1200 K, with an optimal n-type doping concentration of 56×1019 cm-3, resulting in a ZT of 0.68. For IrP3, a ZT of approximately 0.46 is obtained at 600 K and 5 GPa, with a p-type doping concentration of 6.0×1018 cm-3.
The present study provides valuable insights into the behavior of skutterudite materials under strain, offering pathways for enhancing their performance in practical applications.

A first-principles investigation of the structural, optoelectronic, elastic and thermal properties of the p-type half-metallic ferromagnetic perovskites BaFeX3(X = Cl, Br, I)

Abstract The half-metallic nature of the metal halide perovskites BaFeX 3 (X = Cl, Br,I) and their physical properties were studied using Spin-polarised Density Functional Theory calculations. For each structure, ferromagnetic, antiferromagnetic and non-magnetic calculation were performed and the ferromagnetic phase was found to have the lowest energy. The calculated band structures in addition to the electronic density of states confirmed half-metallicity, where the perovskites showed semiconducting nature in the spin up channel and metallic in spin-down channel. The optical properties are calculated and strong absorption in the UV range was seen and the mechanical properties demonstrated mechanical stability with ductile behaviour for all perovskites. The specific heats (at constant volume) of all of the studied perovskites levelled off to about 245 JK−1 mol−1 at high temperatures. The Seebeck coefficient was also calculated as a function of temperature and found to be positive for all the structures which confirm them to be p-type materials. These perovskites are therefore suited for thin film fabrication and bulk single crystals for applications such as UV photodetectors and energy harvesting, in addition to spintronics applications.

High-pressure characterization of Ag3AuTe2: Implications for strain-induced band tuning

Recent band structure calculations have suggested the potential for band tuning in the chiral semiconductor Ag3AuTe2 to zero upon application of negative strain. In this study, we report on the synthesis of polycrystalline Ag3AuTe2 and investigate its transport and optical properties and mechanical compressibility. Transport measurements reveal the semiconducting behavior of Ag3AuTe2 with high resistivity and an activation energy Ea of 0.2 eV. The optical bandgap determined by diffuse reflectance measurements is about three times wider than the experimental Ea. Despite the difference, both experimental gaps fall within the range of predicted bandgaps by our first-principles density functional theory (DFT) calculations employing the Perdew–Burke–Ernzerhof and modified Becke–Johnson methods. Furthermore, our DFT simulations predict a progressive narrowing of the bandgap under compressive strain, with a full closure expected at a strain of −4% relative to the lattice parameter. To evaluate the feasibility of gap tunability at such substantial strain, the high-pressure behavior of Ag3AuTe2 was investigated by in situ high-pressure x-ray diffraction up to 47 GPa. Mechanical compression beyond 4% resulted in a pressure-induced structural transformation, indicating the possibility of substantial gap modulation under extreme compression conditions.

The effect of PBEsol GGA and mBJ potentials on the structural, electronic, optical, elastic and thermoelectric properties of A2BAuI6 (A = K or Rb or Cs, B = Sc or Y)

Perovskites systems are leading the photovoltaic technology now a days. For the consistent renewable energy applications new materials required with the desirable properties. In this work six new materials are being predicted which may be very useful for the renewable energy applications. The full potential scheme of linearized augmented plane wave with the local orbitals is used for the calculations with the PBEsol GGA and mBJ potentials for the exchange-correlation effects. The structural and elastic parameters of A2BAuI6 (A = K or Rb or Cs, B = Sc or Y) are computed, and the responses exhibits that such compounds are stable, have a ductile nature, and are described by a high elastic anisotropy. The bandgaps were identified via the electrical band structure computations for A2BAuI6 (A = K, Rb, Cs; B = Sc or Y) compounds as 1.25 eV, 1.64 eV, 1.24 eV, 1.62 eV, 1.25 eV and 2.04 eV with TB-mBJ + SOC approach. The calculated compounds have much dispersion in their bands and minimal carrier effective mass. Lattice thermal conductivity (KL) is computed via Slack's equation for all computed compounds are 0.29 × 1014 W/mK, 0.31 × 1014 W/mK, 0.29 × 1014 W/mK, 0.31 × 1014 W/mK, 0.39 × 1014 W/mK and 0.29 × 1014 W/mK, indicating a promising future for thermoelectric uses. The calculation of thermoelectric parameters, including the power factor, Seebeck coefficient, and figure of merit, serves another prospective purpose and confirms the potential high use of these materials in thermoelectric devices. Likewise, acceptable quality characteristics like long diffusion length, tunable band-gap, high mobility, am-bipolar charge transport, and high absorption reinforce these compounds which make them even more suitable for photovoltaic applications.

Half‐Heusler Alloy CoMnZ (Z = Sb/Sn): Electrode Material for Lithium‐Ion Batteries

ABSTRACTHeusler alloys (HAs) are a well‐known family of compounds generating promising interest due to their robust structure, ease of tailoring their unique properties, and potential applications. The investigations in the direction of the electrochemical performance of these materials as electrodes for rechargeable lithium‐ion batteries (LIBs) have been established theoretically and experimentally. Alloying of alkali metal ions into half‐HAs unit cells can be another route to improve LIBs performance. This work presents our investigations on thermodynamically stable half‐HAs CoMnZ (Z: Sb/Sn) as electrode materials for rechargeable LIBs using the first‐principle calculations based on the density functional theory. The negative formation energies validate the thermodynamic stability of the alloys considered in this study. With increasing Li doping, a structural change from cubic to tetragonal and orthorhombic phase is observed in the host structure, and upon full lithiation (LiMnZ), a cubic structure is attained. The band structure calculations of the host structure and its lithiated phase indicate a metallic nature in these alloys. The calculations are also performed to investigate the structural stability of parent alloys and corresponding lithiated phases. We calculated a storage capacity of around 14.5 Ah/kg for 0.125 atomic fraction of Li atoms, which is increased by nearly 10 times upon full lithiation. A maximum open circuit voltage of around 9.8 V is calculated for Li0.125Co0.875MnSb and CoLi0.125Mn0.875Sb. Thus, all these remarkable results suggest that these intermetallic compounds have a strong potential as the cathode material for LIBs with a robust life and a large capacity.

Investigation of the Optoelectronic, γ‐Attenuation, and Thermodynamic Properties of Novel MnGa2P3H4NO14 for Energy Applications: A DFT Study

ABSTRACTTransparent conducting oxides (TCOs) from the semiconductor family have garnered considerable interest due to the growing popularity of optoelectronic and thermodynamical applications. Our present study has presented findings on the electronic, optical, and thermodynamic characteristics of spinel oxide MnGa2P3H4NO14; using density functional theory (DFT), we utilized first‐principles calculations carried out with the Wien 2 k software package. The calculations were performed using the generalized‐gradient‐approximation plus Hubbard potential U (GGA+U) method for the doped materials. The band structure calculation reveals that the parent compound exhibits a semiconducting nature and a direct band gap of 2.9 and 1.7 eV for spin‐up and down channels, respectively. The stability of the material is assessed by evaluating its formation energies, which reveal that spinel oxide exhibits the highest stability. The thermodynamic properties are determined using the quasiharmonic Debye model, implemented in the GIBBS 2 code. Furthermore, the quasiharmonic Debye model examines the pressure and temperature dependence of all parameters related to the investigated spinel oxides. In order to evaluate the effectiveness of the radiation shielding, we computed the mass attenuation coefficient for the XCOM program that was investigated from the sample. In addition, linear attenuation, half‐value layer, and mean free path values have been evaluated. A thorough investigation into the dielectric function's optical characteristics was conducted. It has been found that the dielectric function exhibits a wide range of energy transparency. The discovery of UV‐absorbing materials with extremely narrow band gaps suggests their potential use in optoelectronic and solar cell applications. These results provide solid proof and motivation for seeking cutting‐edge optoelectronic materials and technology.

Open Sn Framework Structure Hosting Bi Guest atoms-Synthesis, Crystal and Electronic Structure of Na13Sn26Bi.

The large variety of structures of Zintl phases are generally well understood since their anionic substructures follow bonding rules according to the valence concept. But there are also exceptions, which make the semiconductors especially interesting in terms of structure-property relationships. Although several Na-Sn-Pnictides with a variety of structural motives are known, up to this point no ternary compound in the Na-Sn-Bi system has been described. In this paper we present the Zintl-phase Na13Sn25.73Bi1.27 comprising a complex, open-framework structure of Sn atoms, with one mixed Sn/Bi site, hosting Na atoms. An additional Bi atom is loosely connected with only weak contacts to the framework filling a larger cavity within the network. According to band structure calculations of the two ordered variants with either full occupation of the mixed site with Sn or Bi, resulting in Na13Sn26Bi and Na13Sn24Bi3, respectively, both compounds are semiconductors with band gaps of 0.5 eV. A comparison of the band structures with the structurally related binary compounds Na5Sn13 and Na7Sn12 shows that only the perfectly charge balanced Na7Sn12 is a semiconductor whereas Na5Sn13 is metallic. The rather specific electronic situation in the ternary compound is traced back to the loosely bound Bi atom, which acts as a guest atom according to Bix@Na13Sn26-yBiy, with x=1 and y=0.27, capable to change its oxidation state and thus to uptake additional electrons allowing the system to be a semiconductor. Therefore, Na13Sn25.73Bi1.27 can be understood as a rare example of an open framework structure of Sn atoms comprising Bi atoms in the cavities.

The Effect of Hydrostatic Pressure on Structure, Crystal‐Field Strength, and Emission Properties of Neat and Ni2+‐Activated KMgF3

AbstractTo understand excellent emission and sensitivity for hydrostatic pressure luminescent ions host material, the first principles calculations carried out within density functional theory (DFT) framework are performed to clarify the electronic structure of neat and doped with Ni2+ ions KMgF3 single crystals. The results of band structure calculations show that F2p states are the principal contributors to the KMgF3 valence band, mainly in its upper and central parts, while in the energy band gap of the KMgF3:Ni2+ phosphor, new electronic states associated with the Ni2+ 3d‐orbitals are formed. Furthermore, the zero phonon line (ZPL) spin‐forbidden transition emission energies, (3A2⇄1E) ZPL, (3A2⇄3T2) ZPL, strength of the octahedral crystal field, 10Dq (3A2→3T2)ZPL, are calculated for the KMgF3:Ni2+ phosphor. Any changes of the Em(3A2⇄1E)ZPL transition energy of the KMgF3:Ni2+ phosphor with pressure increasing from 0 to 20 GPa are not detected, while the crystal‐field strength increases linearly with increasing pressure. Present results bring a foresight tool for predicting physicochemical properties of undoped and doped wide‐gap fluorides; KMgF3:Ni2+, without any toxic/harmful or expensive rare‐earth can be effectively used as an optical manometer in 0–20 GPa, which covers the almost whole pressure range available at present in Diamond anvil cell experiments.

Novel superhard orthorhombic O12 carbon: a first principle study

Abstract In this study, a new orthorhombic carbon structure with Ama2 symmetry, designated as O12 carbon, has been predicted on basis of the first-principles method. The thermal stability and dynamic stability of O12 carbon were evaluated and confirmed by combining ab initio molecular dynamics and phonon spectra analyses. Meanwhile, the mechanical properties of O12 carbon, compared with other superhard carbon allostrope like diamond, M-carbon, Bct-c4 and Cco-C8, have also been systematically investigated. With a bulk modulus of 351 GPa, a shear modulus of 333 GPa, and a Vickers hardness of 53 GPa, O12 carbon is identified as a superhard material of significantly technological and industrial applications. The existence of elastic anisotropy in O12 carbon has also been confirmed. The electronic band structure calculations have revealed that O12 carbon exhibits a semiconductor characteristic with a direct band gap of 2.5 eV, making it promising candidate in electronic applications. Additionally, the XRD spectra of O12 carbon were obtained to offer further insights for potential experimental observations. Our findings enrich the family of carbon structure and are expected to stimulate additional experimental interest.

Computational method for angle-resolved photoemission spectra from repeated-slab band structure calculations

Computational method for angle-resolved photoemission spectra from repeated-slab band structure calculations

Buckling-induced variations in electronic, thermal, and optical properties of B[formula omitted]C[formula omitted]N[formula omitted] monolayer: DFT and AIMD computational approaches

Density functional theory is employed to study the novel properties of B3C2N3 monolayer to gain a deeper understanding of variation of electronic, thermal, and optical characteristics arising due to buckling effects. The band structure analysis reveals an energy gap reduction of the buckled B3C2N3 monolayer, causing a displacement of the band gap from the visible to the infrared range. Moreover, the buckling controls the location of the initially, and finally, direct band gap moving it from the K to the Γ point in the B3C2N3 monolayer. The phonon band structure calculations indicate that buckled B3C2N3 monolayers are dynamically stable, while ab-initio molecular dynamics simulations, AIMD, evaluate and confirm the thermal stability of both flat and buckled B3C2N3 monolayers. The buckling phenomenon at low temperatures has no a significant impact on the heat capacity contrary to what happens in the high temperature limit. The optical characteristics of the B3C2N3 monolayer, including refractive index, optical conductivity, static dielectric function, and plasmon frequency, are evaluated at different levels of the buckling parameter. The static dielectric function and plasmon frequency are enhanced with the buckling due to the screening of the electron–electron interactions, affecting the collective oscillations. Enhanced screening gives rise higher plasmon frequencies. Tuning the buckling parameter illustrates the significance of buckling as an alternative mechanism for adjusting the performance of B3C2N3 two-dimensional materials for different technological applications such as solar and optoelectronic systems.

High-Q terahertz chirality enhancement using elliptical hole metasurface

Circular dichroism (CD) technology has garnered significant attention due to its extensive applications in ultra-sensitive biosensing and spin-selective optical frequency conversion. However, existing terahertz chiral structures are constrained by linewidth, which limits their effectiveness in narrowband signal processing. In this study, we propose the notion of quasi-bound states in the continuum (quasi-BIC) within a planar elliptical hole all-silicon terahertz metasurface that exhibits broken mirror symmetry. This approach achieves a CD value as high as 0.97, with a linewidth below 0.5 GHz and a Quality (Q)-factor reaching up to 107 in the 1.3 THz to 1.55 THz band, thereby enabling ultra-narrowband terahertz chirality. This method significantly enhances the Q-factor of optical resonant systems, reduces linewidth, and achieves strong CD while addressing the trade-off between high Q-factor and high CD observed in existing structures. The theoretical foundations for achieving ultra-narrow linewidth are established through band structure calculations and far-field polarization analysis. Additionally, the Q-factor of quasi-BIC can be flexibly optimized through parameter tuning, rendering it more practical than perfect BIC in real-world applications. This study presents a novel solution for terahertz narrowband chirality and optical filters, potentially advancing technologies in related fields.© 2024 Optica Publishing Group under the terms of the Optica Publishing Group Open Access Publishing Agreement.

Structural, Elastic, Electronic, Dynamic, and Thermal Properties of SrAl2O4 with an Orthorhombic Structure Under Pressure.

Its outstanding mechanical and thermodynamic characteristics make SrAl2O4 a highly desirable ceramic material for high-temperature applications. However, the effects of elevated pressure on the structural and other properties of SrAl2O4 are still poorly understood. This study encompassed structural, elastic, electronic, dynamic, and thermal characteristics. Band structure calculations indicate that the direct band gap of SrAl2O4 is 4.54 eV. In addition, the Cauchy pressures provide evidence of the brittle characteristics of SrAl2O4. The mechanical and dynamic stability of SrAl2O4 is evident from the accurate determination of its elastic constants and phonon dispersion relations. In addition, a comprehensive analysis was conducted of the relationship between specific heat and entropy concerning temperature variations.

The structural, elastic, electronic, and optical properties of the rhombohedral La2NiMnO6 double perovskite compound at different temperatures

This study investigates the structural, mechanical, electronic, and optical properties of the rhombohedral La2NiMnO6 (LNMO) perovskite compound at different temperatures using density functional theory. The calculation employed the spin-polarized generalized gradient approximation (GGA). The calculated lattice parameter values agree (less than 1.2 % difference) with experimental values. We determined the mechanical properties using elastic constants calculated from the stress-strain relationship. The elastic constants obtained satisfy the Born stability criteria for the rhombohedral structure. Electronic band structure calculations revealed that LNMO exhibits the suitable narrow band gap semiconductor character in the spin-polarized state. Finally, the real and imaginary parts of the dielectric function and other optical functions along the x and z directions are calculated and interpreted.

Tailoring the electronic properties of TiO2 monolayers for solar driven catalysis through transition metal doping

Substitutional doping with transition metals is carried out in the Lepidocrocite phase - the stable monolayer geometry of TiO2, using density functional theory (DFT) methods. The doping is carried out at the differently coordinated O atom cites, producing Janus monolayer geometries. Our results indicate that key fundamental properties for photocatalysis can be tuned via doping. Monolayers doped with Ag, Au, Pd and Pt are thermodynamically stable, amongst all considered doping possibilities, as evident from phonon band structure calculations. Electronic structure of the Janus monolayers alters significantly, compared to pristine TiO2, owing to the emergence of mid-gap states. Reduced band gap arises from upward shift of the valence band, suggesting enhanced visible-light response. Dopant atoms also introduce excess electrons in TiO2 monolayers, which are found to localize at a single Ti site. This induces ferromagnetism in the doped monolayers. Furthermore, charge separation between TiO2 and noble metal dopants is observed which is a key parameter in influencing the selectivity and activity of photocatalytic materials. Compared to the pristine TiO2 monolayer, the Janus structure can promote water adsorption, and the Janus monolayers exhibit significantly improved activity in the hydrogen evolution reaction. These findings suggest that engineering a novel Janus TiO2-based monolayer with a noble metal layer on the other surface can offer a potential approach to improve photocatalytic performance over pristine TiO2.

Synthesis, structure and characterizations of the first alkali-metal/alkaline-earth-metal oxalatophosphate Na4Mg3(HPO4)4(C2O4)·2H2O

The first alkali-metal/alkaline-earth-metal oxalatophosphate Na4Mg3(HPO4)4(C2O4)·2H2O with monoclinic P21/n space group was successfully synthesized by a conventional solvothermal method. Na4Mg3(HPO4)4(C2O4)·2H2O crystal exhibits a typical three-dimensional structure built by isolated [C2O4] and [HPO4] anionic groups connected by Na and Mg atoms. The HPO42− groups are linked by hydrogen bonds to form an unique one-dimensional zigzag band ∞[HPO4]2-, which exhibits a stable “Mortise-Tenon” structure configuration within the bc plane. Fourier transform infrared (FTIR) spectrum and Raman spectrum confirm the crystal structure of Na4Mg3(HPO4)4(C2O4)·2H2O. UV–visible near infrared (UV–Vis–NIR) diffuse reflectance and band structure calculation indicate that Na4Mg3(HPO4)4(C2O4)·2H2O is an indirect bandgap semiconductor with a bandgap of 4.42 eV. In addition, Na4Mg3(HPO4)4(C2O4)·2H2O shows a moderate birefringence of 0.046 at 550 nm.