Born Stability Research Articles

DFT study of halogen based double perovskite Na2AgAlX6 (X = Cl, Br, I) double perovskites for energy harvesting applications

Abstract Double perovskites halides show a lot of potential for being utilized in energy converting applications. This research offers a wide-ranging analysis of photovoltaic features of halogen based double perovskite Na2AgAlX6 (X = Cl, Br, I) by employing DFT approach. Structural, thermoelectric and optoelectronic features of Na2AgAlX6 have been analyzed in this report. The structural stability of the investigated materials is verified by Born's stability criterion. The ductility of Na2AgAlX6 is confirmed by the Poisson coefficient ( >0.27) and a Pugh ratio (B/G>1.83). The bandgap 3.7 eV, 2.7 eV, and 1.3 eV of Na2AgAlX6 (X = Cl, Br, I) has been observed with direct nature. The replacement of Br and I with Cl leads to the lowering of bandgap value because it brings the edges of the band closer together. The absorption factor, reflective properties, and dielectric parameters are used to evaluate the optical features. The BoltzTraP software played vital role in calculating the thermoelectric characteristics, such as ZT value, power factor, and their electrical and thermal conductivities.The results of these calculated properties indicate that Na2AgAlX6 (X = Cl, Br, I) double perovskite halides show a promising potential for energy renewable applications.

Study of inorganic perovskite RGaO3 (R = Rb and Na) oxide alloys for photocatalytic applications: A DFT insights

Photocatalytic technology has been hailed as one of the most promising ways to alleviate and potentially avoid both the global energy environment and consumption issues. In this regard, the perovskite RGaO3 (R = Rb and Na) oxides are investigated for water splitting applications. DFT based CASTEP code is utilized by employing GGA-PBE exchange-correlation functional. According to structural analysis, compounds have 221 space groups (cubic) with 5 atoms. The structural analysis and band structures of NaGaO3 and RbGaO3 crystals were described as having an indirect bandgap with 3.11 eV and 2.15 eV energy, respectively. Absorption, reflectivity, loss function, conductivity, refractive index, and dielectric function were all explored in terms of optical characteristics. According to the mechanical properties, compounds RGaO3 (R = Rb and Na) are mechanically stable, ductile, anisotropic, and hard by Born stability. These materials are best suited for photocatalytic applications to produce H2 fuel with the highest efficiency.

Computational insights of double perovskite X2CaCdH6 (X = Rb and Cs) hydride materials for hydrogen storage applications: A DFT analysis

Perovskite materials play a backbone role in materials science to investigate various applications including photocatalytic, photovoltaic, and hydrogen storage. Hydrogen storage is a modern technique to fulfill energy consumption and demands. We inspect the structural, hydrogen, electronic, optical, and thermodynamic properties of X2CaCdH6 (X = Rb and Cs) perovskite substances for hydrogen (H2) storage applications. The research shows substances have 225 Fm3m cubic natures and 40 atoms. The formation and cohesive energies of the examined structures show that X2CaCdH6 (X = Rb and Cs) substances may be produced and are thermodynamically stable. Electronic characteristics indicate that substances are semi-metallic, with correspondingly indirect bandgap Eg energies of 2.13 eV and 2.30 eV. The mechanical stability (Born stability), brittle (B/G = 1.22, 1.15 and α = 0.17, 0.18), hard (6.255, 5.481), and anisotropic (0.278, 0.171) of the X2CaCdH6 (X = Rb and Cs) perovskite substances are demonstrated by the examined elastic values. The Debye temperature ΘD (289.395, 320.837)K, melting temperature Tm (646.961, 650.714)K, acoustic velocities (vm, vl, vt) m/s, minimum thermal conductivity Kmin (0.63, 0.75) (W/mK), and Grüneisen parameter (18.121, 19.521) of substances are also computed by investigating their thermodynamic characteristics. Cs2CaCdH6 and Rb2CaCdH6 have gravimetric ratios of 1.39 wt% and 1.69 wt%, correspondingly. Our findings shed light on using double perovskites X2CaCdH6 (X = Rb and Cs) as a hydrogen (H2) storage substance.

Pressure-induced lead-free halide double perovskite [formula omitted] for optoelectronic applications

The structural, electronic, optical, mechanical and thermodynamic properties of the lead free double perovskites Rb2CuSbX6(X=Cl,Br) were investigated using first principles based on density functional theory (DFT) under pressure. Our calculated results are in good agreement with other experimental results. Electronic and optical features are pressure dependent, including dielectric effect, pressure-dependent refractive index changes, strong UV reflectivity, suggesting potential applications in solar heating reduction. Using the Voigt-Reuss-Hill approximation, an increase in stiffness, of Rb2CuSbX6(X=Cl,Br) is observed with increasing loads, revealing its stability, making it appropriate for shaping. By analyzing the formation energy and Born's stability criteria, we justified the stability to check the mechanical and thermodynamic stability of the material. In addition, the mechanical properties of Rb2CuSbX6(X=Cl,Br) conducted with the study of elastic constants, elastic moduli, machinibility index, Kleinmen parameter and Vickers hardness. Our investigation indicates that both the materials provide significant potential for very high-quality optical data using optoelectronic applications.

First-principle simulations of inorganic halides Li2TlBiY6 (Y = Cl, Br, I) for optoelectronic applications

In this emerging technological era, lead-free (Li-based) inorganic halides have drawn a lot of researchers’ consideration due to their optoelectronic applications. Based on this, we explored theoretically mechanical, optical, and thermoelectric features of halides Li2TlBiY6 (Y = Cl, Br, I) by employing first-principle simulations (Wien2k code). Our finding of optoelectronic parameters using appropriate mBJ approach is in favorable alignment to previously reported data, and PBEsol is employed to scrutinize structural as well as mechanical features of these materials. The Born stability and formation energy are examined concerning the structural stability associated with all halides. The distinction between brittle and ductile nature is investigated concerning the calculation of elastic constants of the cubic symmetry. Being based on the mBJ potential, the bandgasps for Li2TlBiCl6, Li2TlBiBr6, and Li2TlBiI6 are 2.8 eV, 2.3 eV, and 1.9 eV, correspondingly. To confirm their optimal absorbability in the electromagnetic domain (visible), all halides were further analyzed concerning dielectric parameters. Additionally, thermoelectric properties are explained in detail within the temperature range of 300-800K using classical Boltzmann theory, making them promising materials for thermoelectric applications.

DFT simulation to study the physical properties of ternary intermetallic materials ACuSb (A=Ca, Sr, Ba) for solar cell and TBC materials

This study carried out the configurational, bulk, electronic, optical as well as thermodynamic features of ternary materials ACuSb (A = Ca,Sr, Ba) using first-principles DFT-based calculations. The explored lattice constants as well as unit cell volume are very close to hypothetical results which make sure the correctness of the present study. According to the investigated elastic stiffness constants, the studied compounds are mechanically stable as they hold the Born's stability criteria. Utilizing the calculated values of elastic constants the several polycrystalline parameters such as elastic moduli (B, Y, E), machinability index (μm), hardness (HV), Poisson's ratio, Pugh's and isotropic/anisotropic factor of ACuSb (A = Ca,Sr, Ba) have been calculated and discussed in details. Very high machinability indices of these phases ensure their industrial applications. Since the values of Poisson's and Pugh's are ν < 0.26 and B/G < 0.75, therefore the phases ACuSb (A = Ca,Sr, Ba) show brittle manner. The direction-dependent features of these materials are confirmed from the Universal anisotropy factor analysis. Band structure analysis reveals that every compounds exhibit metallic character. Bond population analysis revealed the different covalent and ionic bonding tendencies in these compounds, with apparent differences in the nature of Cu–Sb bonds. Furthermore, the absorption coefficients of BaCuSb ensures its excellent suitability for solar cell applications, as it demonstrated remarkable UV-range absorption capabilities, distinguishing it from the other compounds in this regard. The thermal analysis demonstrated that these compounds exhibit remarkably low thermal conductivity, indicating their appropriate applications in thermal barrier coating (TBC) materials.

DFT based Investigation of Structural, Thermodynamic, Mechanical and Electronic Properties of RuVZ (Z: As, Bi, Sb) Half-Heusler Semiconductors

Half-Heusler (hH) alloys are an intriguing class of materials with significant potential for applications in spintronics, thermoelectrics, optoelectronics, and magnetoelectronics due to their unique adjustable properties. In this work, we have investigated the structural, thermodynamic, mechanical, and electronic properties of RuVZ (Z: As, Bi, Sb) half-Heusler materials using the density functional theory (DFT) as implemented in the quantum espresso computational suite. The structural, thermodynamic, and mechanical properties were also predicted using the linear response density functional perturbation theory. We observed that the hH alloys are non-magnetic semiconductors and have an indirect narrow band gap. The band gap values and lattice constants for RuVSb and RuVAs cubic crystals are consistent with published reports. RuVBi has a lattice constant of 6.18 and a band gap of 0.16 eV. The elastic parameter results obtained satisfy Born's stability requirements, suggesting mechanical stability of the hH materials. All three alloys are found to be ductile. The RuVZ alloys obey the Dulong-Petit law at heat capacity of 74.7, 74.5, and 74.3 J mol-1K-1 and temperatures of 556, 754, and 775 K, respectively. The Debye temperature of 353.75K suggests that the RuVAs alloy is the hardest, with a significant Debye sound velocity (2997.12 m/s) and will have high thermal conductivity.&#x0D;

Temperature-Dependent Ultrasonic Properties of Semiconducting M&lt;sub&gt;2&lt;/sub&gt;CO&lt;sub&gt;2&lt;/sub&gt; (M= Ti, Zr, Hf) MXenes

Here, we have studied the elastic, ultrasonic, mechanical, and thermal behavior of temperature-dependent hexagonal oxygen-functionalized M2CO2 (M= Ti, Zr, Hf) MXenes. The higher-order linear and nonlinear elastic constants, viz., second-order (SOECs), and third-order (TOECs) have been computed using the Lenard Jones interaction potential model. For mechanical characterization, bulk modulus (B), shear modulus (G), Young's modulus (Y), Pugh's ratio (B / G), Poisson's ratio, and anisotropic index are evaluated using SOECs. Born's stability and Pugh's criteria are used to examine the nature and strength of the MXenes in all the temperatures. For the investigation of anisotropic behavior and its thermophysical properties, temperature-dependent ultrasonic velocities and thermal relaxation time have been calculated along with different orientations from the unique axis of the crystal. The ultrasonic attenuation (UA) of a longitudinal and shear wave due to phonon-phonon (p-p) interaction and thermoelastic relaxation mechanism were investigated for these oxygen-functionalized MXenes. Thermal conductivity is a principal contributor to the behavior of UA due to p-p interactions. Our analysis suggests that semiconductor Ti2CO2 MXenes show superior mechanical properties to other oxygen-functionalized MXenes. Computed elastic, ultrasonic, and thermal properties are correlated to evaluate the microstructural behavior of the materials useful for industrial applications.

Probing the electronic, optical and transport properties of halide double perovskites Rb2InSb(Cl,Br)6 for solar cells and thermoelectric applications

Halide-based double perovskites have recently been promoted as high-performing semiconductors for photovoltaic and thermoelectricity applications owing to their outstanding efficiency, non-toxicity and ecological stability. In the framework of this research, we have systematically investigated the structural, mechanical, electronic, optical, and thermoelectric properties of Rb2InSb(Cl,Br)6 double halide perovskites. Based on Born stability and tolerance factor criteria, we have found that Rb2InSb(Cl,Br)6 are mechanically and structurally stable. Furthermore, we have performed a comprehensive evaluation of the electronic, optoelectronic, and thermoelectric characteristics. From the electronic band structure results, Rb2InSbCl6 and Rb2InSbBr6 exhibit direct semiconducting band gaps of 1.41 ​eV and 0.53 ​eV, respectively. The optical parameters of Rb2InSb(Cl,Br)6 reveal that our active structures have a higher dielectric constant, with maximum absorption in the visible range reaching over 5.68 ​× ​105 ​cm−1 and high optical conductivity (2.19 fs−1 for Rb2InSbCl6 and 2.14 fs−1 for Rb2InSbCl6). Moreover, the maximum limited spectroscopic efficiency reaches an impressive value of approximately 28.0% for Rb2InSbBr6 and 33.7% for Rb2InSbCl6. The thermoelectric properties were accurately calculated using the BoltzTraP simulation package. The obtained results reveal a significant electrical conductivity, a strong Seebeck coefficient (S ​≈ ​2756 μVK−1 ​at 300 ​K), and an average figure of merit close to one for both structures (ZT ​≈ ​1). Our findings suggest the versatility of these materials and could be used for a wide range of applications, including commercial solar cells and thermoelectricity.

A computational study for mechanical, thermoelectric and optoelectronic applications of BiAlO3 under static pressure

Inorganic perovskites have a wide area of applications in low-cost optical and thermal applications. This manuscript aims to present Structural, mechanical, electronic, optical, as well as thermoelectric behavior of perovskite compounds BiAlO3 (BAO) for optoelectronic as well as thermoelectric applications, a novel energy production mechanism under high static pressure. Thermal stability is computed by enthalpy relation and also confirmed by elastic moduli. Physical properties are measured at ground state energy, and also explored pressure impact up to 100 GPa on electronic structure of BiAlO3. BAO shows an indirect band gap at 0–30 GPa, while it transforms to a direct with an increase in pressure. Mechanical stability was confirmed by applying Born's stability criteria. Even at higher pressure it remains in cubic phase and show mechanically stable structure. Optical responses are calculated and compared under pressure. With an increase in pressure, a clear blue shift was observed. The refractive index of refraction showed a decreasing trend from 3.32 to 2.84 from o to 100 GPa, respectively. Thermoelectric properties are explored by computing electric and thermal conductivity, Seebeck coefficient and power factor. The efficiency of the devices depends upon the figure of merit (ZT) i.e. the ratio of electrical to thermal conductivity must be small. The figure of merit indicated that at low temperature (lower than room temperature and normal pressure) the ZT can reach 0.7, if at high pressure, it can be larger than 0.8. Promising results of thermoelectric response under stress indicate that the said material is suitable for thermoelectric properties. BAO is not only led free but also environment friendly thus, the eventual candidate for devices based on optoelectronics and thermoelectric applications due to relevant bandgap nature after asserting pressure and its thermoelectric nature.

INVESTIGATION OF INTERMETALLIC GdFeAl TERNARY COMPOUND BY ELASTIC, THERMOPHYSICAL AND ULTRASONIC ANALYSIS

Higher order elastic constants were calculated of the intermetallic GdFeAl ternary compound using Lennard Jones potential approach. With the using of second order elastic constants (SOECs), other elastic moduli; shear modulus, bulk modulus, Young’s modulus, Pugh’s ratio, constants of elastic stiffness and Poisson’s ratio are estimated for mechanical and elastic characterization at room temperature. Born stability and Pugh's criteria are used to examine the nature and strength of the intermetallic ternary compound and found that it is mechanically stable compound. For the investigation of anisotropic behaviour and thermophysical properties, ultrasonic velocities and thermal relaxation time have been also calculated along with different orientations from theunique axis of the crystal. The temperature variation of ultrasonic velocities, Debye average velocity and thermal relaxation time along the z axis is evaluated using SOECs. The ultrasonic properties correlated with elastic, thermal and mechanical properties which is temperature dependent is also discussed. Ultrasonic attenuation was calculated at different temperatures due to phonon –phonon (p –p) interactions. The responsible reason of attenuation is p-p interactions; it was got that the thermal conductivity is a core contributor to the characteristic of ultrasonic attenuation as a role of temperature.GdFeAl ternary compound behave as its purest form at lower temperature and are more ductile demonstrated by the minimum attenuation

Pressure-induced elastic, mechanical and opto-electronic response of RbCdF3: A comprehensive computational approach

The structural, mechanical, and opto-electronic properties of cubic RbCdF3 (c-RCF) under high pressures were probed using a Generalized-Gradient Approximation (GGA-PBE) within the fram work of CASTEP. The aim of this study is to see how pressure affects structural and electronic properties and in response of electronic change how optical behaviour altered along with mechanical properties. The calculated structural properties such as the equilibrium lattice parameter (4.59 Å), the bulk modulus (63.7821) and its pressure derivative are in good agreement with the available data at pressure 0 GPa. The obtained results for the band structure and the total density of states (TDOS) show that the RbCdF3 has an indirect band gap of 2.863 eV. The changing electronic properties affect optical response which was studied and discussed. The refractive index (n(ω)) decreases from 2.6 to 1.72 gradually with increasing pressure. The elastic constants were calculated using the energy deformation relationship, from these constants the other mechanical properties such as bulk modulus, shear modulus, Young modulus and Poisson ratio were calculated and commented. The results of elastic constants established that RbCdF3 is mechanically stable at each pressure because it fulfills the Born's stability criteria. RbCdF3 behaves as brittle at low pressure when we increased pressure it shows ductile nature in this study. Poisson ratio (σ) and Cauchy pressure also confirm similar behaviour. Lastly, the anisotropy factor was discussed. RCF is thus a fascinating material for optoelectronic devices, thermoelectric and piezoelectric properties.

DFT investigation of mechanical and vibrational properties of CuTe

The electronic, mechanical, vibrational and thermal properties of CuTe have been investigated using the PBEsol functional within the scope of the density functional theory. The electronic properties are investigated after optimizing the crystal structure and it is found that CuTe is a metal in ambient conditions. The elastic constants satisfy Born's stability criterion. Mechanical properties suggest that CuTe is highly anisotropic. In particular, the bulk modulus is found quite large along the b-axis. Anisotropy of elastic moduli and wave velocities suggest anisotropy in thermal conductivity. The minimum thermal conductivity is observed along [001] direction. The supercell method is applied to get phonon dispersion curves and the Raman and Infrared active modes are analyzed. The frequencies and the symmetry of the most of optic modes are in agreement with earlier results.

Optoelectronic and thermoelectrical and mechanical properties of CdLu2X4 (X = S, Se) using first-principles calculations for energy harvesting applications

First-principles study of spinel compounds CdLu2X4 (X = S, Se) has been carried out using density functional theory based Wien2k code. Lattice parameters are consistent with the experimental data. Born's stability criteria confirm the mechanical stability, while the Poisson coefficient (ν > 0.26) and the Pugh ratio (B0/G > 1.75) certifies the ductile nature of the compounds. Tran and Blah modified Becke-Johnson exchange potential was employed, which gives accurate values of direct bandgap 2.08/1.44 eV for CdLu2S4/Se4. The maximum absorption of photon energy in the visible to the ultraviolet region is found. The high absorption in ultraviolet and visible regions makes them good candidates for solar cells and energy storage devices. Thermoelectric properties are studied using BoltzTrap code in terms of electrical and thermal conductivity, Seebeck coefficient, power factor, and figure of merit.

Cubic Germanium monochalcogenides (π-GeS and π-GeSe): Emerging materials for optoelectronic and energy harvesting devices

Newly discovered cubic phase of Germanium monochalcogenide (π-GeS and π-GeSe) with a moderate bandgap, less toxicity, and novel electronic properties have earned significant attention of researchers due to appropriate nature for the energy-related applications such as photovoltaic, optoelectronic and thermoelectric devices. The structural, electronic (band structure and DOS), optical and elastic properties of π-GeS and π-GeSe have been studied by ultrasoft pseudopotential technique. The band structure calculations confirm that both π-GeS and π-GeSe are indirect in nature with bandgap energies 1.38 and 1.04 eV respectively. The first-time calculated elastic constants of π-GeS and π-GeSe satisfy their mechanical stability criteria (Born stability). The elastic moduli (bulk, Young’s, shear), Lame’s parameters, Poisson’s ratio, Debye temperature, and average sound velocity are determined by Voigt-Reuss-Hill approximation. The shear and Young’s elastic properties reveal that both π-GeS and π-GeSe are anisotropic, which is also confirmed from 2D and 3D surface visualization. The calculated Debye temperature (θD) of π-GeS and π-GeSe are 262.28 K and 264.46 K at 300 K, respectively. Additionally, the longitudinal and transversal waves sound velocities are calculated for the first time in [1 1 1], [1 1 0] and [1 0 0] directions. The present results reveal that π-GeS and π-GeSe could be appropriate candidates for exploitation in energy storage, optoelectronic and thermoelectric devices. Particularly GeS, which has higher absorption peaks and optimum bandgap (1.38 eV) for practical photovoltaic and photo-sensing applications. The present work provides the pathways for theoretical and experimental studies on electronic devices based upon cubic chalcogenides.

Pressure-induced phase transition and elastic properties of barium chalcogenides

Two-body, Born–Mayer type potential considered up to the third nearest-neighbor interaction have been used to investigate the B1–B2 phase transition and elastic properties of barium chalcogenides at high pressure. The computed values of B1–B2 phase transition pressure, equation of state (compression curve), bulk modulus, and its first-order pressure derivative are given along with the available experimental and other theoretical values. This study supports the Born's stability criterion and shows that the third nearest-neighbor interaction has an important role to predict the B1–B2 phase transition pressure in barium chalcogenides.

STRUCTURAL PHASE TRANSITION IN BORON COMPOUNDS AT HIGH PRESSURE

The high-pressure induced structural phase transitions and pressure induced elastic and anharmonic behavior of boron compounds viz. BN, BP, and BAs have been investigated using an inter-ionic potential approach based on charge transfer effect. These compounds go to NaCl phase (B1) under pressure from zinc blende phase (B3). The variations of second-order elastic constants and their combinations follow a systematic trend with pressure, identical to that observed in other compounds of zinc blende structure family. Shear stiffness constants decrease with increasing pressure up to phase transition pressure. The bulk moduli of these compounds are in reasonably good agreement with other theoretical and experimental data. The values of phase transition pressure of these compounds obtained by using the present approach are also in good agreement with those predicted by using the pseudo potential approach. The present approach has also succeeded in predicting the Born and relative stability criterion for stable zinc blende phase of these compounds. We also present a set of third-order elastic constants and pressure derivatives of second-order elastic constants for boron compounds.

Study of elastic properties and their pressure dependence of lanthanum monochalcogenides

An effective interionic interaction potential (EIOP) approach is employed for the description of phase transitions and equations of state of lanthanum monochalcogenides LaX {X=S, Se, Te} compound semiconductors. The long-range Coulomb, van der Waals (vdW) interaction and the short-range repulsive interaction up to second neighbor ions within the Hafemeister and Flygare approach with modified ionic charge are properly incorporated in an EIOP. We have obtained a reasonably good agreement between the present theoretical and available experimental values on the phase transition pressures (P t=25.5, 12.4 and 16.8 GPa) and elastic properties in all materials under consideration. The associated volume collapses at the phase transitions have been found to be 8.1%, 10.4% and 7.2% for lanthanum monochalcogenides. The vast volume discontinuity in pressure volume phase diagram identifies the structural phase transition from NaCl type (B1) to CsCl type (B2) structure. The variations of elastic constants and their combinations with pressure follow a systematic trend identical to that observed in other compounds of NaCl type structure family. The present approach has also succeeded in predicting the Born and relative stability criteria.

Ab-initio Lattice Instability Analysis on Ni and Ni3Al Single Crystals

The purpose of the present study is to elucidate the “ideal strength” of the Ni and Ni3AI single crystals, the main compositions of Ni-based superalloy, from the viewpoint of the lattice stability. The unit lattices of Ni and Ni3Al, fcc and L I2 ordered alloy, are subjected to the [001] uniaxial tension/compression and hydrostatic tension/compression by using the Vienna Ab-initio Simulation Package (VASP) with the generalized gradient approximation (GGA) and ultrasoft pseudopotential. The elastic stiffness matrix is numerically evaluated at each point in the applied deformation pass, then the lattice stability is discussed based on the positiveness of the matrix. Both Ni and Ni3Al reaches the Born's stability criteria against the bifurcation to the anisotropic Poisson's contraction in the [001] uniaxial tension, while they do the spinodal criteria against the structural transformation in the [001] uniaxial compression and hydrostatic tension. The hydrostatic compression increases the stability and shows no limit, however, it is also suggested that the spinodal instability appears when the ideal isotropy was broken. The “ideal strength” is evaluated with these stability limits and indicated as “yield curve” on the normal strain-lateral strain or normal stress-lateral stress planes.

Embedded atom potentials in fcc and bcc metals

A new embedded atom potential has been proposed in this paper. The potential is expressed by simple functions and is applicable to the molecular dynamics simulations of large atomic systems. The potential parameters are determined from the experimental data using the cohesive energy, Born stability, elastic constants, C 11, C 12 and C 44, the formation energy of a vacancy. In case of fcc the stacking fault energy is also used to fit parameters. The potential functions for copper, silver and gold for fcc metals and for bcc metals Nb, Ta and Va are presented.