Band Structure Plots Research Articles

Investigating the structural, electronic, optical and thermodynamic properties of ATiO3 (A = Ba, Ca, Ra) for low-cost energy applications

The structural, optoelectronic, and thermodynamic characteristics of ATiO3 (A = Ba, Ca, Ra) perovskites have comprehensively been investigation first-principles based DFT calculations. The GGA method was employed to handle exchange and correlation potentials. The analysis of the E-V plots indicates that RaTiO3 exhibits the highest level of stability in comparison to BaTiO3 and CaTiO3. The direct band-gap characteristic of the ATiO3 (A = Ba, Ca, Ra) perovskites is apparent in the band structure plots. The band gaps for BaTiO3, CaTiO3, and RaTiO3 are 2.48, 3.15, and 1.91 eV, respectively. The analyzed materials exhibit the highest level of photon absorption in the near UV area, as demonstrated in the ε2(ω) plots. The refractive index n(ω) values reveal that ATiO3 (A = Ba, Ca, Ra) are active optical materials as their n(ω) values are between 1 and 2. These perovskite oxides have optical features that make them promising prospects for anti-reflecting coatings over entire energy span as these materials exhibits a very low reflection (∼20 %) of incident photons. The thermodynamic properties of ATiO3 (A = Ba, Ca, Ra) are assessed to determine their dynamical stability and suitability for thermal applications. The results of the investigation demonstrate that these perovskite oxides have the potential to be used in optoelectronic devices.

First-principles calculations to investigate Electronic, Optical, Mechanical, and transport characteristics of novel A2BAuCl6 (A = K/Rb/Cs; B = Sc/Y)

By utilizing FP-LAPW, the structure, electronic, optical, mechanical and Transport characteristic of A2BAuCl6 (A = K/Rb/Cs, B = Sc/Y) were examined by using DFT. The analysis to the band structure plot of the Halide double perovskites (HDP’s) being studied indicated the existence of indirect band-gaps. The compounds A2BAuCl6 (A = K/Rb/Cs, B = Sc/Y) exhibit anisotropic properties, except one compound as seen by their respective shear anisotropy readings of 0.629, 0.532, 1.006, 0.682, 0.803 and 0.977. The materials have inherent ductility, as indicated by their calculated Poisson’s ratios in the range of 0.30 to 0.35. The examined (HDP’s) materials appear to possess indirect band-gaps, as indicated by the band structure plots. The functional inorganic perovskites A2BAuCl6 (A = K/Rb/Cs, B = Sc/Y) haven’t similar band-gap values, as determined using the TB-mBJ (modified Becke Johnson) and TB-mBJ + Soc (Spin orbital coupling) assumptions. The visible and ultraviolet domain have prominent peaks, suggesting potential applications of the compounds in solar cells. Moreover, examination of additional optical characteristics such as reflectivity, conductivity, electron energy loss, and absorption coefficients suggest that it possesses the inherent features of a semiconductor. The maximum figure of merit for all the student compounds is above 0.74. The simulated output forms the foundation for A2BAuCl6 (A = K/Rb/Cs, B = Sc/Y) and are of practical importance for multijunction solar cells.

Computational exploration of Cs2LiMoX6 (X=Cl, I) halide double perovskites: Unveiling energy storage potentials

Density functional theory (DFT) simulations were conducted to investigate the physical characteristics of materials Cs2LiMoCl6 and Cs2LiMoI6. The magnetic and electronic features were examined using the Perdew, Burke, and Ernzerhof generalized-gradient approximation (PBE-GGA). Confirmation of the semiconductor behavior was attained through the spin-resolved density of states (DOS) and band structure (BS) plots. In this investigation, the computed band gap (Eg) values for Cs2LiMoI6 are identified as 0.96 eV in the spin-down channel and 1.76 eV in the spin-up channel. Likewise, for Cs2LiMoCl6, the Eg is determined to be 3.35 eV in the spin-down channel and 1.63 eV in the spin-up channel. From magnetic characteristics, the magnetic moments (μB) of 3.02436 μB and 3.00332 μB are calculated for Cs2LiMoCl6 and Cs2LiMoI6, respectively. The ferromagnetic (FM) nature is observed from the integral values of the magnetic moment. The Mo-4d-t2g orbitals play a pivotal role in determining the magnetic properties observed in perovskite materials. The study also explored optical properties, and the values of ε1(ω) at zero energy are approximately 4.84 and 3.20 for Cs2LiMoI6 and Cs2LiMoCl6, respectively. The maximum values of σ(ω) are observed to be 4631 (Ω cm)−1 and 3618 (Ω cm)−1 at 6.24 eV and 8 eV for Cs2LiMoI6 and Cs2LiMoCl6, respectively, signifying their suitability to the UV light region. Overall, these findings suggest the suitability of both materials for photovoltaics and other related applications.

Energy gap and aromatic molecular rings.

The manuscript combines rational density functional theory simulations and experimental data to investigate the electrical properties of eight polycyclic aromatic hydrocarbons (PAHs). The optimized geometries reveal a preference for one-row, two-row and three-row ring distributions. Band structure plots demonstrate an inverse correlation between the number of aromatic rings and band gap size, with a specific order observed across the PAHs. Gas phase simulations support these findings, though differences in values are noted compared to the literature. Introducing a two-row ring distribution concept resolves discrepancies, particularly in azulene. The B3LYP function successfully bridges theoretical and experimental gaps, particularly in large PAHs. The manuscript highlights the potential for designing electronic devices based on different-sized PAHs, emphasizing a multi-ring distribution approach and opening new avenues for practical applications.

FP-LAPW study of structural, magnetic, electronic, elastic, and thermoelectric properties of CoCrS Half-Heusler compound

The present article has utilized the WIEN2k computational code to examine the structural, elastic, electronic, magnetic, thermoelectric, and dynamic aspects of the CoCrS Half-Heusler (HH) compound. In this work, calculations have been performed by utilizing the full-potential linearized augmented plane wave method using density functional theory. The electronic bandgap was better interpreted by using the modified Becke–Johnson exchange–correlation functional. We evaluated various electronic properties of the CoCrS HH compound, including band structure plots and density of states. Furthermore, we examined the magnetic characteristics through the computation of magnetic moments and the examination of the spin-polarized electronic state behavior. We also determined the elastic properties of the CoCrS HH compound. These properties, which include stiffness, resilience, and general stability, provide important information about how the material responds to mechanical deformation. Moreover, we explored the electronic structure and found that type 5 of CoCrS exhibits a metallic behavior. In addition, we examined the compound’s thermoelectric properties. Finally, the dynamical properties indicate that type 5 of CoCrS is dynamically stable.

First-principles study of structural, electronic, mechanical, optical, thermodynamic and thermoelectric properties of ternary ZnSnN2 and ZnMoN2 nitrides

This paper mainly reports structural, electronic, mechanical, optical, thermodynamic and thermoelectric properties of ternary ZnSnN2 and ZnMoN2 nitrides. Calculations are carried-out (using Wien2k software) to examine the properties of ZnSnN2 and ZnMoN2 nitrides. Both nitrides have negative formation energies confirming their structural and thermodynamic stability. Electronic band structure and DOS plots show semiconducting nature of ZnSnN2 (with a direct band gap = 0.23 eV), while semi-metallic behavior of ZnMoN2. Mechanical properties indicate the brittle behavior of both (ZnSnN2 and ZnMoN2) nitrides. Calculated mechanical properties show anisotropic behavior of ZnSnN2 and ZnMoN2 nitrides. Both nitrides show an average reflectivity of about 20–35% (in the visible region) which show their suitability to enhance light absorption in solar panels and also their use for anti-reflective coatings in optical devices. For ZnSnN2 and ZnMoN2 nitrides, thermodynamic properties are also calculated at different pressures (0–100 GPa) and at different temperatures (0–2000 K). Thermoelectric properties are calculated using Boltztrap2 code. High figure-of-merit (ZT = 2.38 of ZnSnN2 at room temperature) reflects its suitability to use in thermoelectric systems. Combination of electronic optical and thermoelectric properties indicate that the ZnSnN2 and ZnMoN2 nitrides have great potential for use in electronic, optical and thermoelectric devices.

Theoretical investigation of structural, electronic, elastic, and optical properties of rubidium-based perovskites RbSrX3 (X = Cl, Br) for optoelectronic device applications – A DFT study

The search for environment-friendly lead-free halide perovskites is an emerging research area due to their crucial application in the field of photovoltaics and optoelectronics. So, in this current work, the structural, electronic, elastic, thermal, and optical properties of rubidium-based cubic halide perovskites RbSrX3 (X = Cl, Br) are investigated by the full potential linearized augmented plane wave (FP-LAPW) method in the context of density functional theory (DFT). The Generalized Gradient Approximation (GGA) of Perdew-Burke-Ernzerhof (PBE) is implemented as the exchange-correlation potential. The structural stability of these compounds in the cubic phase is studied and the values of their formation energies and ionic filling fraction (IFF) have been assessed. The band structure and DOS plots reveal a wide indirect bandgap at zero pressure. The elastic constants of these compounds are evaluated, and from Blackman's and Every's diagrams, they are found to be elastically stable with a ductile and anisotropic nature. The optical parameters of these compounds imply that they show good response in the ultraviolet region. Thus, by experimentally synthesizing these compounds their potential application in the development of optoelectronic devices working in UV range can be assessed.

Thermoelectric, mechanical, and pressure sustained half-metallic properties of BaInO3 perovskite for spintronics applications: DFT computation

Oxide perovskites continue to promote research interest because of their concurrent use in spintronic and thermoelectric applications. The electronic, magnetic, and thermoelectric properties of new half-metallic BaInO3 perovskite are investigated using the density functional theory. The structural and thermodynamic stability of the proposed perovskite is provided by the tolerance factor, octahedral factor, formation energy, and phonon dispersion curves. The structural relaxation curves reveal that the ground state is ferromagnetic. The generalized gradient approximation and mBJ band structure plots show that the half-metallicity exclusively results from the strong exchange splitting of 2p-bands at the Fermi level. Compared with PBE, mBJ depicts highly localized magnetic moments around oxygen along with enhanced half-metallic gaps and band gaps in the spin-up channel. Under a compressive strain, the system undergoes a magnetic phase transition from half-metallic ferromagnet to non-magnetic metal at 30 GPa. The elastic stability at the studied pressure range has been verified from Blackman’s and Every’s diagrams. The material remains ductile and exhibits moderate elastic anisotropy in the studied pressure range. The quasi-harmonic Debye model is employed to study the temperature and pressure effects of thermodynamic parameters. The computed transport properties including the Seebeck coefficient and spin-Seebeck coefficient predict reasonable thermoelectric performance in generating thermally induced spin-polarized current and spin current, respectively. Such a detailed study of this material could open prospects in spintronic as well as waste energy recovery devices.

A systematic first-principles investigation of the structural, electronic, optical, thermodynamic and transport properties of lead-free pyrochlore oxides Q2Sb2O7 (Q= Be, Ca, Sr) for low-Cost energy applications

A systematic study has been performed on structural, optical and thermophysical properties of newly designed pyrochlore oxides Q2Sb2O7 (Q = Be, Ca, Sr) employing FP-LAPW based first-principles calculations. The GGA approach was used to treat exchange and correlation potentials. The investigated E-V plots reveals that Sr2Sb2O7 is the most stable structure compared to Be2Sb2O7/Ca2Sb2O7. A direct energy bandgap of 0.29 eV is evident from band structure plot of Be2Sb2O7, however, Ca2Sb2O7/Sr2Sb2O7 possess indirect energy bandgaps of magnitude 1.47/1.467 eV. The studied materials show maximum absorption of incoming photons in near UV region as shown in ε2(ω) plots, however, considerable absorption in visible region is also present. Ca2Sb2O7/Sr2Sb2O7 are effective optical material with a n(ω) value between 1.0 and 2.0. Optical properties of pyrochlore oxides reveal that these materials are potential candidates for shielding materials in upper UV region. A photon reflection of up to 60% is evident from the R(ω) in UV region, however, in IR and visible regions, the reflectance is negligible. Based on calculated values of Seebeck coefficient (S), we can state that Be2Sb2O7 is n-type semiconductor whereas Ca2Sb2O7/Sr2Sb2O7 are p-type semiconductors. The most effective thermoelectric material among Q2Sb2O7 (Q = Be, Ca, Sr) is Ca2Sb2O7 as its ZT value is highest (∼1.05) in the entire temperature range. Thermodynamic properties of Q2Sb2O7 (Q = Be, Ca, Sr) are also evaluated to check dynamical stability and appropriateness of these materials in thermal applications. The investigated outcomes show that these pyrochlore oxides are potential candidates for thermoelectric and optoelectronic device applications.

A computational study of TiHfPtZ (Z = Al, Ga, In) quaternary heusler compounds for spintronics applications

First-principles calculations were employed to investigate the structural, phonon, electronic, and magnetic properties of newly designed quaternary Heusler compounds (TiHfPtZ; where Z = Al,Ga,In) for spintronics applications. The phonon dispersion reveals that new quaternary heusler compounds are dynamically stable. Density of states and band structure plots of TiHfPtZ (Z = Al,Ga,In) compounds shows the half-metallic nature with indirect energy band gaps 1.07 eV, 0.92 eV and 0.99 eV at the Fermi level in spin down channel respectively. Each system displays a magnetic moment of 3μ B, which favors the half-metallic ferromagnetism and follows the Slater Pauling rule Mt = At −24 (Mt: total magnetic moment and At: total number of valence electrons). Moreover, Curie temperature was determined in each cell is 566 K.

Electronic and half-metallic behaviour of manganese doped SiC Zigzag nanotubes using density functional theory

Single walled SiC nanotubes have gain centre of attraction due to the unique behaviours and potential application in the field of optoelectronics devices, LED, storage materials, and Photovoltaic materials. Electronic and structural properties of intrinsic and Manganese (Mn) doped SiC Zigzag nanotubes verified using first principle calculations associated with Density functional theory (DFT). Band gap of SiC Zigzag nanotubes influenced the structural and optical properties which play a crucial role in semiconductor application and create new opportunities in optoelectronic components. Electronic band plot of intrinsic SiC Zigzag nanotubes indicates band gap increased with the increase diameter of the nanotubes. PDOS plot shows 2p orbitals and 3p orbitals has major contribution on mostly filled valence band and lowest filled conduction band region whereas 2 s and 3 s orbitals of C atom and Si atom has minor contribution. Band structure plot of Mn doped SiC Zigzag nanotube introduced an extra energy layer in conduction band and resulting decrease the band gap value and valence band and conduction band cross the Fermi energy level in DOS plot representing the half-metallic characteristics which has different potential applications specially in photovoltaic materials. Half-metallic materials have outstanding spin transport characteristics. Spin-polarized electrons can effectively have conducted by Sic Zigzag nanotubes that controlled transport of spins. These half-metallic properties are essential for spintronic materials where electron spin used for information storage and processing. PDOS plot of Mn doped SiC Zigzag nanotube indicate 2p and 3p states of C atom and Si atom has major contribution compared to the 2 s and 2p states of C atom and Si atom whereas 3d orbitals of dopant Mn atom has major contribution near Fermi level of both conduction and valence band. This study highlights the potential optoelectronic applications of Mn doped SiC Zigzag nanotubes.

An ab‐initio study of structural, opto‐electronic and thermoelectric aspects of zinc sulfide and zinc telluride

AbstractIn this study, structural, electronic, optical and thermoelectric aspects of Zinc Sulfide (ZnS) and Zinc Telluride (ZnTe) have been explored in detail. These calculations have been done by utilizing FP‐LAPW method via Density Functional Theory (DFT). In order to attain accurate band gaps, opto‐electronic properties are evaluated with modified Becke Johnson potential (mBJ). From band structure plots, both ZnS and ZnTe reveals direct (Γv–ΓC) band gap semiconductors in nature with bandgap value equal to 3.5 and 2.3 eV while in Density Of States (DOS) major influence is observed due to p states of S/Te and d state of Zn. Prominent variation of optical responses such as high values of imaginary dielectric constants 𝜀1 (ω) and n (ω) refractive index suggests that ZnS and ZnTe are applicant materials for future photonics and microelectronic devices. The thermoelectric aspects were explored by Boltz Trap code to determine electrical and thermal conductivities, Seebeck coefficients, power factors and figure of merit. The figure of merits is closer to 1 while compared with p‐type ZnS and ZnTe, n‐type ZnS and ZnTe has good thermoelectric properties, which are attributed to low thermal conductivity of the hole and larger effective mass. The goal of this research is to investigate not only the detailed physical aspects but also to provide an overview of its future applications in optoelectronics, displays, sensors and microelectronic industry.

Investigation on prospective thermoelectrics — cubic Nd-doped LMO and rhombohedral Cu4Mn2Te4 materials — first principles approach

Structural, electronic, magnetic and optical properties of Cu4Mn2Te4 have been reported earlier by the authors, and here, the transport properties of the same are discussed along with the band structure investigation of the neodymium-doped cubic material LMO (LiMn2O4), namely LiMn[Formula: see text]Nd[Formula: see text]O4 compound, under spin polarized schemes through the First Principles calculations. The Full Potential-Linearized Augumented Plane Wave Method (FP-LAPW) method is adopted to investigate the electronic structures based on the framework of Density Functional Theory (DFT). Exchange potentials are treated using the Generalized Gradient Approximations (GGA). Cohesive energy calculations reveal that the ferromagnetic phase of LiMn[Formula: see text]Nd[Formula: see text]O4 and the antiferromagnetic phase of Cu4Mn2Te4 exhibits a stable phase. Of these, FM-LiMn[Formula: see text]Nd[Formula: see text]O4 shows a semi-metallic-like behavior in spin-up channel and metallic behavior in spin-down channel whereas antiferromagnetic Cu4Mn2Te4 exhibits a band gap in both spin-up and spin-down channels. Dirac points are identified at −0.0625[Formula: see text]eV in the band structure plot of FM-LiMn[Formula: see text]Nd[Formula: see text]O4 at its high symmetry points [Formula: see text] and W which is an indication of high electron mobility at ambient condition. The presence of flat and dispersive bands around the Fermi energy level is an indication of high thermopower, and it is present in both the compounds FM-LiMn[Formula: see text]Nd[Formula: see text]O4 and AFM-Cu4Mn2Te4. From the present computations, at 300[Formula: see text]K, a power factor range of ([Formula: see text] scaled by relaxation time in [Formula: see text]W/msK2) [Formula: see text] and [Formula: see text] is obtained for ferromagnetic LiMn[Formula: see text]Nd[Formula: see text]O4 compounds at up and down spins, respectively. A typical power factor ([Formula: see text]Wm[Formula: see text]s[Formula: see text]K[Formula: see text]) of [Formula: see text] and [Formula: see text] is obtained for antiferromagnetic Cu4Mn2Te4 at 325[Formula: see text]K required for good thermoelectric performance.

A DFT study: Tailoring opto-electronic and thermoelectric performance of K2SeX6 (X = Cl, Br) double perovskites for solar cell advancements

Density functional theory (DFT) has been used to examine the structure, optoelectronic, elastic, and thermoelectric characteristics of K2SeX6 (X= Br, Cl) utilizing the full potential linearized augmented plane wave (FP-LAPW). The examined double perovskites (DPs) appeared to feature indirect band gaps, according to the electronic band structure plots. K2SeX6 (X= Cl, Br) have computed shear anisotropy values of 0.55 and 0.54, respectively, indicating they are anisotropic materials. The materials' computed Poisson's ratios of 0.25 and 0.26 suggest that they are naturally ductile. According to the band structure plots, the examined DPs appear to feature indirect band gaps. The band gap values of two functional inorganic/organic perovskites, K2SeBr6 and K2SeCl6, are strikingly close to 2.0 eV and 1.689 eV. (Using modified Becke Johnson (mBJ) approximations). Because the maximum peaks occur in the visible and ultraviolet regions, they suggest potential solar cell applications for the materials. K2SeX6 (X=Br, Cl) has good values for electron production, great potential for applications in the optoelectronic sector. Additionally, it is a semiconductor by nature, according to the results of other optical characteristics such as absorption coefficients, electron energy loss, conductivity, and reflectivity. Because the maximum peaks occur in the visible and ultraviolet regions, they suggest potential solar cell applications for the solids. For K2SeX6 (X= Cl, Br), the computed Seebeck coefficient at 100 K, the S values attained 299.9 μV/K and 219 μV/K, respectively, are positive, demonstrating p-type conduction. Both K2SeBr6 and K2SeCl6 have a figure of merit values that are more than one (ZT > 1) 300K range which indicates that they are effective thermoelectric materials, but after these values of temperature, the zTe values vary. The computations' findings are the foundation for K2SeX6 (X= Cl, Br) and are practically applicable to solar cells.

A DFT Approach and Perspective of Sodiation in Ag2O Host: Exploration towards Sodium Batteries

Inspired by the high volumetric energy density and biocompatibility of Ag2O, the exploration of sodiation mechanism with one and two Na atom(s) per Ag2O unit cell has been carried out. Here, Na adsorbed at tetrahedral interstitial site (TIS) of Ag2O emerges to be the most stable with energy of –6.98 eV leading to the formation of Na–Ag2O compound. The advancement of Ag2O towards a metallic state is evidenced by the absence of a forbidden energy gap in the band structure plot with Na inclusion. Also, the formed compound is confirmed from PDOS plots and by analysing the charges transferred between Na, Ag and O atoms from CDDP. Further, when the concentration of Na is stepped up to two, the most stable TIS and Agsub sites exhibits an energy of –5.79 eV Na−1 atom. In this case, the Bader charge analysis reveals that Na prefers to form strong contacts with Ag and weak interactions with O, thus demonstrating the feasibility of alloying rather than the conversion product. Subsequently, NEB studies show that the surface diffusion of Na from one TIS to the adjacent unit requires a minimal activation energy thereby suggesting the suitability of Ag2O as an alloying host.

Subwavelength grating-based silicon photonic TE mode division multiplexer for C + L band operation

This paper reports a subwavelength grating (SWG) based multiplexer (MUX) on a silicon photonics platform capable of multiplexing three transverse electric modes. The designed MUX is simulated using a commercial 3D finite-difference time-domain solver and shows broadband operation over the whole C and L optical telecom bands from 1530 nm to 1625 nm wavelength range. The effective indices of the Bloch modes in the SWG waveguides are extracted from the band structure plot. The designed MUX consists of two co-directional coupling regions for fundamental to higher-order mode coupling, with each coupling stage consisting of single-mode and multimode SWG waveguides. The transmission characteristics, viz. transmittance, insertion loss, and return loss, are presented and discussed. The coupling lengths without the tapering regions for TE0–TE1 and TE0–TE2 mode couplings are 14μm and 1.48μm, respectively. The transmittance is >78% with the highest insertion loss and return loss of 1.1 dB and –15 dB, respectively. At 1550 nm, the transmission is >88%, insertion loss is <0.6 dB, and return loss is <−15 dB. A uniform under-etch and over-etch of 5 nm are taken for the fabrication tolerance study, which shows a maximum variation of 0.58 dB for the insertion loss with return loss <−14.6 dB at 1550 nm. Over the whole simulated range, the insertion loss is <1.4 dB, and return loss is <−14.6 dB with ±10 nm change in device dimension. A temperature tolerance study with 50 °C and 100 °C rise in temperature has been done, and the device retains its broadband operation over the simulated range. The maximum increase in insertion loss is 0.1 dB for the TE0–TE2 coupling, while the overall return loss of the device decreases to <−20 dB for the TE0–TE1 coupling.

Spin-orbit coupling and electronic properties in Pt2MnGa: an ab-initio study

The electronic and magnetic properties of full-Heusler alloy Pt2MnGa with and without the effect of spin–orbit coupling are studied. The calculations have been carried out using ab initio density functional theory. Both the magnetic spin orders of Pt2MnGa, ferromagnetic and antiferromagnetic, are considered. It is found that the ferromagnetic spin arrangement is the most stable spin order at the ground state, regardless of the incorporation of spin–orbit coupling. The density of states and band structure plots are used to validate the obtained ground state structure, which is further validated by the Bader charge analysis and the charge density distribution of the individual atoms. The obtained results of magnetocrystalline anisotropy energy, total magnetic moment, Curie temperature, and the spin-polarization hint at the possible application of this compound in spintronics devices such as bit-patterned media.

Scrutinized the spin-orbit coupling effect on the elastically and thermodynamically stable Rb2BCl6 (B = Pb, Ti) double perovskites for photocatalytic, optoelectronic and renewable energy applications

In this report, the electronic structure, mechanical stability, optoelectronic, thermoelectric and photocatalytic response of inorganic halide perovskites Rb2BCl6 (B= Pb, Ti) have been simulated first time by using density functional theory (DFT). Modified Becke-Johnson (mBJ) potential along with spin-orbit coupling (SOC) effect is applied for accurate calculations. The calculated ground-state lattice parameters, negative formation energy values and positive phonon frequencies endorse the stability of both compounds. The band structure plots display the semiconductor character of both perovskites. The mechanical stability has been determined with the Bulk and Young modulus, Poisson ratio, along with the calculation of elastic constants. The calculated optical response reveals a high dielectric constant and absorption coefficient with low reflectivity. These compounds are revealed to have a higher figure of merit (ZT) than the typical metal halide perovskites with the values of 0.732 and 0.72 for Rb2PbCl6 and 0.724 and 0.71 for Rb2TiCl6 at 800K with mBJ and mBJ+SOC, respectively. The Seebeck coefficient and figure of merit present good values at high temperatures. The photocatalytic activity has shown the water-splitting ability of Rb2TiCl6. The overall analysis of the calculated properties shows that the studied halide perovskites are suitable for optoelectronic, thermoelectric and photocatalytic applications.

A DFT study of optoelectronic, elastic and thermo-electric properties of the double perovskites Rb2SeX6 (X=Br,Cl)

Thermo-electric (TE) material applications reduce reliance on traditional energy resources by converting heat to electric energy. We have studied, for the first time, the thermo-electric properties of Rb2SeX6 (X=Br,Cl). Using norm-conserving pseudo potentials in a plane wave basis set of Quantum Espresso code, the optoelectronic, elastic and thermo-electric properties of Rb2SeX6 (X=Br,Cl) have been investigated using density functional theory. Generalized Gradient Approximation of Perdew Burke Ernzerhof (GGA-PBE) and Generalized Gradient Approximation of Perdew Burke Ernzerhof adapted for Solid (GGA-PBESol) exchange correlation functionals were employed in all calculations. The band structure plots suggest that the studied double perovskites have indirect band gaps. Rb2SeBr6 band gap values of 1.7574/ 1.569 eV (using GGA-PBE/PBEsol) are remarkably similar to that of two effective inorganic/organic perovskites FAPbI3 and MAPbI3 . Maximum peaks generated from refractive index results indicate possible solar cell uses of the materials because they are in the visible and ultraviolet ranges. The results of other optical properties such as absorption coefficients, electron energy loss, conductivity, and reflectivity concludes that Rb2SeX6 (X=Br,Cl) have good values for electron generation, high potential for applications in the optoelectronic industry and are semiconductor in nature. The calculated shear anisotropy values of Rb2SeBr6/Cl6 are 3.09/1.71, suggesting that they are isotropic materials. With calculated Poisson’s ratio of 0.32 and 0.26, the materials are predicted to be ductile in nature. The two materials are appropriate for thermo-electric applications since their thermal to electrical conductivity ratio are small (the order of 10-5). The calculated minimum values of Seebeck coefficient values of 0.198×103 / 0.166 ×103 (mV/K) at 750 K, for Rb2SeBr6/Cl6 are positive, indicating that they have p-type conduction. Figure of merit values at all temperature range considered are greater than one (ZT &gt; 1) for both Rb2SeBr6 and Rb2SeCl6, suggesting that they are good thermo-electric materials. The results of the calculations provide the basis for the industrial application of Rb2SeBr6/Cl6 as solar cells.

Investigation on Co-based half-Heusler alloy: A DFT approach

Metallic half-Heusler alloy CoNiSb is investigated under first-principle formalism by Quantum Espresso package. The density of states and electronic band structure plot confirms the metallic nature of this alloy. Elastic coefficients are also computed for this cubic structure and then various mechanical properties such as bulk modulus, shear modulus, Young’s modulus, and Poisson's ratio are estimated. These obtained values suggest the better rigidity, and hardness of this alloy. Owing to this metallic behaviour with good mechanical properties and non-corrosive features of this alloy due to cobalt, this alloy can be bio-compatible material and can be used for medical implants and surgeries.