Mechanical Stability Criteria Research Articles

Temperature dependence of the mechanical properties of Heusler [formula omitted] and [formula omitted] using the Quasi-Harmonic Approximation

The study of electronic properties of Fe2TiSi and Fe2TiSn using two functionals GGA and meta-GGA confirms the semiconductor nature of these alloys. This result enables us to compute elastic constants within Quasi-Harmonic Approximation without considering the electronic contribution. These elastic parameters decreased as the temperature increased with respect to the mechanical stability criteria of Born. Poisson’s and Pugh’s ratios indicate that both alloys have ionic bonding and are brittle. From the Vicker’s Hardness values, both alloys are found to be hard. Finally, we found that the mechanical properties of Fe2TiSi are more sensitive to temperature changes than those of Fe2TiSn; however, the former is harder than the latter over the temperature range of 0K to 1000K. The good mechanical properties make Fe2TiSi and Fe2TiSn a good solution for use as thermoelectric generators and waste heat recovery.

Exploring the half-metallic ferromagnetism, dynamical and mechanical stability, optoelectronic and thermoelectric properties of K2NaMI6 (M = Mn, Co, Ni) for spintronic applications

The structural stability, optoelectronic and magnetic characteristics of K2NaMI6 (M = Mn, Co, and Ni) halide double perovskites have been demonstrated to be explained using density functional theory computations. The prominent generalized gradient approximation and integration of the mBJ potential are implemented to estimate the exchange–correlation potential, which is the only unidentified parameter in the state-of-the-art formulism. The structural optimization, mechanical stability criteria, and tolerance factor demonstrate the reliability of the double perovskites in a cubic structure with Fm3m symmetry. The elastic constants facilitated mechanical stability and revealed the brittle nature of these double perovskites. The spin-polarized electronic band profile and the behaviour of the dielectric constant and absorption coefficient in the spin-up and down channels show the presence of half-metallic nature in these materials. Additionally, we examined magnetism and the genesis of the half-metallic gap in this article. The half-metallic and magnetic properties are attributed to the unpaired electrons in the split d-orbitals of the M-sited elements in the crystal field. The Mn-, Co-, and Ni-based double perovskites were found to possess total magnetic moments of 4 μB, 4 μB, and 1 μB, respectively, with the transition metal atoms comprising up the majority of this magnetic moment. The Fermi level’s perfect spin polarisation promotes the potential application of double perovskites in spintronic technology.

Enhancement of optical properties of two-dimensional Bi2Te2Se by biaxial strain based on first-principles

The study of two-dimensional flexible materials in mechanic and optics has gained significant attention. By applying strain to modify the internal structure of materials, researchers can investigate the resulting mechanical and optical changes, offering exciting opportunities for further exploration in this field. The electronic structure, mechanical properties, and optical properties of the two-dimensional trigonal system Bi2Te2Se under biaxial strain regulation were investigated by using the first-principles plane pseudopotential plane wave method based on density generalized function theory. The analysis reveals that the energy bandwidth of Bi2Te2Se decreases with increasing strain until the band gap reaches 0 at 9% strain, causing the system to shift from a semiconductor to a conductor. The electronic density of states is primarily determined by the 6p orbitals of Bi and 5p orbitals of Te. With regards to its mechanical properties, Bi2Te2Se satisfies the mechanical stability criterion under different strains. As the strain increases from 0% to 6%, the material becomes increasingly brittle, with its interior transitioning from metallic to covalent bonds. However, the material toughness begins to improve from 6% to 9%, with the interior transitioning from covalent to metallic bonding. The performance improvement of Bi2Te2Se varies depending on the two electric field polarization vectors along [1 0 0] and [0 0 1] directions under strain. The material shows distinct application prospects in terms of absorption coefficient, reflectivity, refractive index, and lossiness under two directions. This paper provides a theoretical reference for the future mechanical and optical applications of Bi2Te2Se.

Structural stability and physical properties of MAX phases M2SX (M=Sc, Y, X=B, C, N) via first-principles calculations

The structural, mechanical, lattice-dynamic, anisotropic, electronic and thermal properties of M2SX (M=Sc, Y; X=B, C, N) are investigated based on density functional theory. The calculated results indicate that all the phases satisfy the thermodynamic, mechanical and dynamic stability criteria. The mechanical properties are in good agreement with the reported values, and the results show that Sc2SN exhibits the highest bulk modulus B (145.7 GPa), shear modulus (103.0 GPa) and Young’s modulus E (250.0 GPa) with brittle behavior. The elastic anisotropy of M2SX indicates that Sc2SC is the most isotropic among the 6 phases. The electronic structure reveals that Sc2SC and Y2SC are indirect-bandgap semiconductors with 0.927 eV and 1.260 eV bandgap, and the other phases exhibit metallic characteristics. The Debye temperature, lattice thermal conductivity, minimum thermal conductivity, heat capacity and entropy have also been calculated for M2SX phases. The tendency for lattice thermal conductivity in high temperature: K lat (M2SN) > K lat (M2SC) > K lat (M2SB). All the present calculated data will provide useful guidance for development and research on the novel S-based MAX phases in the future.

First-principles calculations of phase transition, elasticity, phonon spectra, and thermodynamic properties for ThO2 polymorphs

First-principles calculations based on density generalized function theory (DFT) were used to determine the structural transformation, phonon spectra, thermodynamic properties, and elastic behavior of ThO2 under compressive and tensile loading in this work. In compressive conditions, the transition pressures and calculation of structural parameters agree with the experiment results. Phase transitions of ThO2 from the Fm3‾m phase to the Pnma, P42/mnm and Pnnm phases under tensile conditions were anticipated to happen at 23.2 GPa, −7.69 GPa, and −7.75 GPa, respectively. Within the range of pressures analyzed, both the Fm3‾m and Pnma phases of ThO2 exhibit mechanical stability, but the P42/mnm phase and Pnnm phase are unstable at high pressures, according to the mechanical stability criteria, which is validated concerning elastic constants. Under ambient pressure, the calculated phonon spectra of the ThO2 polymorphs in this study demonstrate that all of the phases taken into consideration are dynamical stability. Also, the predicted heat capacities, isothermal bulk modulus, Gibbs free energies, and thermal expansion coefficients of ThO2 polymorphs as functions of temperature are analyzed and are in comparison with relevant experiments.

First-principles calculations to investigate structural, electronic, elastic, optical and transport properties of halide double perovskites Cs2ABF6 (AB = BiAu, AgIr, CuBi, GaAu, InAs, InAg, InAu, InSb and InBi) for solar cells and renewable energy applications

The first-principles calculations are used for a comprehensive study of the novel halide double perovskites by using the CASTEP code which is based on DFT. The correlational function of the GGA-PBE with the ultra-soft pseudo potential USP plane wave was utilized to carry out the present study. For all novel halide double perovskites, the lattice parameters were determined first, and the compounds were subjected to the mechanical stability criteria. From 0.56 to 4.99 eV, the Cs2ABF6 materials are found to be direct band-gaps. The dielectric functions of the materials of interest are large near and in the middle ultraviolet regions. They become smaller in the far and extreme ultraviolet regions. Furthermore, the Cs2ABF6 are found to be elastically stable, ductile, anisotropic and relatively low hard materials. A comprehensive analysis of the optoelectronics and thermoelectric nature with a given band gaps are carried out. This reflects the use of Cs2ABF6 in solar cells, energy storage devices, photovoltaic devices, radiation detectors, photonic crystals, light emitting diodes and thermoelectric generators. Thermoelectric coefficients such as the figure of merit thermal and electrical conductivities, Seebeck coefficient (S), and are also examined to check the possibility of these materials in the field of thermoelectric. The computed value of ZT reflects (ZT ∼ 1) Cs2ABF6 materials and reveals that such type of materials holds a virtuous route toward thermoelectric applicability.

Ni2ZnAl BİLEŞİĞİNİN İLK PRENSİPLER YÖNTEMİ İLE İNCELENMESİ

In this study, ground state properties of Ni2ZnAl alloy in L21 phase from Heusler family were optimized. The calculated parameters are in harmony with the available literature data. Elastic constants were calculated using optimized parameters. The calculated elastic constants were found to meet the Born mechanical stability criteria. By using these constants, some mechanical and thermodynamic properties of the material such as elastic modulus, Vicker hardness, anisotropic nature, melting temperature were investigated in detail. Calculations showed that the Ni2ZnAl alloy is ductile, soft, and anisotropic. As such, it is a candidate material for applications that do not require hardness. The free energy, vibrational energy, entropy, and heat capacity of the Ni2ZnAl alloy were investigated using a semi- harmonic approach in the range of 0-800 K. All the total energy calculations were performed using the open-source Quantum Espresso software and ab-initio pseudopotential method based on the density functional theory (DFT) scheme within a generalized gradient approximation (GGA). According to the data obtained because of the study, Ni2ZnAl alloy is a potential candidate for industrial use.

BIOPHARMACEUTICAL INVESTIGATION OF ANTIOXIDANT GEL

Introduction: With the recognized association between oxidative stress and skin diseases, incorporating antioxidants into treatment strategies has gained importance. However, dermatological dosage forms containing antioxidants are underrepresented on the pharmaceutical market. The search for delivery systems that ensure antioxidant stability and enhance antioxidant effects on the skin remains is quite relevant. Among the various dosage forms, gels have gained significant interest in recent times.
 The purpose of this study work is to conduct a comparative biopharmaceutical investigation of gels containing the synthetic antioxidant ethylmethylhydroxypyridine succinate (EMHPS) at different concentrations of the active ingredient.
 Materials and methods: The study utilized gel compositions containing EMHPS at concentrations ranging from 2.5% to 7.5%. Synthetic polymer compounds were employed as gelling agents, and the gels were prepared under laboratory conditions according to the technological scheme developed by the author. The obtained samples were assessed for thermal, colloidal, and mechanical stability. The release rate of EMHPS from the gels was determined by the dialysis method using a semipermeable membrane according to Kruchinsky. Dialysate samples were collected over a 5-hour period and analyzed spectrophotometrically at 297 nm. The data obtained were checked for normal distribution and statistically processed using Excel tables.
 Results: The studied gels exhibited thermal and colloidal stability, no delamination occurred under elevated temperature and centrifugation conditions. The gels and their bases demonstrated mechanical stability, with respective values ranging from 1 to 2. Analysis of the dialysis results revealed that the release of the active substance from all three gel samples commenced after 15 minutes, exhibited intensive increase within the first 60 minutes, and continued to gradually increase from 1 to 4 hours. Although the fraction of released active substance remained consistent across the three gels at each time interval, the absolute EMHPS amount in the dialysate depended on the drug concentration
 In conclusion, synthetic-based gels containing EMHPS can be successfully formulated, meeting the criteria of thermal, colloidal, and mechanical stability. These gels demonstrated the ability to release 47-49% of the active substance within the first 30 minutes, proportional to its concentration

Study of the Electronic Band Structure and Structural Stability of Al(CN)2 and Si(CN)2 by Density Functional Theory

By substituting the A site in P21/c-A(CN)2 and varying the lattice parameters a, b, c, and the unit-cell angles, along with using crystal graph convolutional neural networks to calculate their cohesive energy, the candidate compounds, Al(CN)2 and Si(CN)2, were selected from the structure with the lowest cohesive energy. The two candidate structures were then optimized using first-principles calculations, and their phonon, electronic, and elastic properties were computed. As a result, two dynamically stable structures were found: Al(CN)2 with a space group of Cmcm and Si(CN)2 with a space group of R3¯m. Their phonon spectra exhibited no imaginary frequencies; thus, their elastic constants satisfied the mechanical stability criteria. Structurally, Si(CN)2 is similar to 6H-SiC and 15R-SiC. Its elastic constants indicated that it is harder than those SiC materials. Al(CN)2 exhibits metallic properties and the indirect wide-bandgap of Si(CN)2 was calculated by the generalized gradient approximation, the local density approximation, and the screened hybrid functional of Heyd, Scuseria, and Ernzerhof (HSE06) is found to be 3.093, 3.048, and 4.589 eV, respectively. According to this wide bandgap, we can conclude that Si(CN)2 has the potential to be used in high-temperature and high-power environments, making it usable in a broad range of applications.

Screening of ABF3 fluoroperovskites by using first-principles calculations

The CASTEP code based on DFT is used to investigate the fluoroperovskites with the general formula ABF3. The correlational function of the GGA-PBE with the ultra-soft pseudo potential USP plane wave was utilized to carry out the present study. For all fluoroperovskites, the lattice parameters were determined first, and the compounds were subjected to the mechanical stability criteria. The B/G ratio was utilized to determine the ductility or brittleness in the stable compounds. Then, the Poisson's ratio was used to verify the ductileness in the stable compounds. The Debye temperature and Cauchy pressure were also determined accordingly. The electronic properties were studied for the compounds which were proved ductile according to the Pugh's criteria and Poisson's ratio. Among the ductile compounds, CdSbF3 was found to have a band gap of 0.257 eV while zero band gap was found in all the other compounds. All the other materials possess the metallic nature due to having zero band gap. As a result of its semiconducting nature, CdSbF3 is found to be the best material for various applications.

First‐Principles Calculations for the Enhancement of Mechanical Properties of High‐Entropy Alloys by Carbon Elements

AbstractA series of alloy solid solution models were developed using the SQS modeling method, and the effect of C doping on the phase structure, elastic properties, and electronic structure of the alloys was investigated using a first‐principles approach. The results showed that the CuCrWNi (C), CuCrWMo (C), and CuCrWAl (C) alloys all have a single body‐centered cubic (BCC) structure. The alloys conformed to the mechanical stability criterion before and after incorporating C. The incorporation of C leads to an increase in the bulk modulus B of the CuCrWNi, CuCrWAl alloy, and the Young's modulus E and shear modulus G of the CuCrWMo, CuCrWAl alloy. In comparison, the shear modulus G and Young's modulus E of CuCrWNi alloy and the bulk modulus B of CuCrWMo alloy show a decreasing tendency. The alloy is ductile before and after the addition of C. The addition of C increased the Poisson's ratio, Pugh ratio, and Cauchy pressure of CuCrWNi alloy and decreased the Poisson's ratio, Pugh ratio, and Cauchy pressure of CuCrWMo and CuCrWAl. This shows that adding C improves the ductility of CuCrWNi and the strength of CuCrWMo and CuCrWAl alloys. By analyzing the electronic structure of the alloys, it was found that the doping of C made the alloy less stable. Adding C makes the high‐entropy alloys more conducive and the metallic properties more noticeable. Moreover, the incorporation of C makes the CuCrWNi pseudo‐energy gap decrease and the CuCrWMo, and CuCrWAl pseudo‐energy gap increase, which may be related to the change in the mechanical properties of the alloy. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Theoretical exploration of the structure and physical properties of YbZn2X2 (X = N, P, As, Sb)

In this study, we conduct a comprehensive theoretical analysis of the structural parameters, dynamic stability, elastic properties, and optoelectronic characteristics of YbZn2X2 (X = N, P, As, Sb). The phonon dispersion calculations imply that YbZn2N2 is dynamically stable. For the first time, we investigate the elastic constants of YbZn2X2, and our findings show that the obtained elastic constants meet the mechanical stability criteria. The analysis of electronic properties shows that YbZn2X2 (X = N, Sb) and YbZn2X2 (X = P, As) are direct and indirect band gap semiconductors, respectively. The band gaps of these compounds vary between 0.3 and 1.8 eV, and the energy gap is decreased from N to Sb. The results imply that YbZn2As2 displays an optimal band gap of approximately 1.2 eV and a high optical absorption coefficient with an order of 105, making it a promising candidate for optoelectronic devices. These findings offer valuable insights for further exploration of the performance of these compounds in optoelectronic applications.

Elastic stability criteria of seven crystal systems and their application under pressure: Taking carbon as an example

Elastic stability criteria are widely employed to prove the being of the lattice. Sin'ko and Smirnov have reported the applicable criteria under isotropic pressure and given the equations between the elastic constants C ~ i j and C i j under pressure. On this basis, the closed forms of necessary and sufficient conditions for elastic stability in all crystal classes have been presented, which are popular in normal pressure. However, the forms of elastic stability criteria under pressure are still fragmented in various literature studies. Carbon is an element with a rich variety of allotropes, and because of its excellent mechanical and electronic properties, it gains enduring and intense attention, while its phase diagram is poorly known. In order to systematically study the response of various carbon stabilities to pressure and offer some valuable insights into experimental exploration, we derive the total forms of mechanical stability criteria under isotropic pressure and calculate the mechanical stability of 46 carbon allotropes involving seven crystal systems under pressure.

First-principles study on the optoelectronic properties of the quasi-one-dimensional flexible semiconductor K2PdPS4I

Inorganic semiconductors have superior electrical properties than organic semiconductors, but their application in some devices, such as wearable electronic devices, is subject to the limitations of their brittleness. Low-dimensional flexible inorganic semiconductors have superior electrical properties than organic semiconductors, but their application in some devices, such as wearable electronic devices, is subject to the limitations of their brittleness. Low-dimensional flexible inorganic semiconductors are promising candidates to overcome these disadvantages. Therefore, we pay our attention to a quasi-one-dimensional (Q-1D) chain-like material K2PdPS4I and explore its structural stability, electronic structure and optical properties by first-principles calculations. The phonon spectrum of K2PdPS4I is dynamically stable without any imaginary frequency. Furthermore, the orthorhombic crystal structure of K2PdPS4I meets the mechanical stability criterion according to the calculated elastic tensors. K2PdPS4I exhibits anisotropic mechanical properties and belongs to the ductile materials. K2PdPS4I is an indirect bandgap semiconductor with obviously anisotropic carrier effective masses and mobility, showing excellent light absorption ability in the visible and ultraviolet regions. The superior mechanical performance and excellent optoelectronic properties enable K2PdPS4I as a candidate material for promising applications as low-dimensional flexible optoelectronic semiconductors. The present study not only provides a meaningful supplement for the research of low-dimensional semiconductors, but also will attract extensive interest from a wide audience to explore the Q-1D materials.

Phase stability and physical properties of lanthanum dicarbide under pressure

ABSTRACT First-principles calculations of electronic parameters, mechanical and dynamical stabilities on superconducting properties of the body-centered tetragonal intermetallic lanthanum dicarbide LaC2 have been reported at zero and high pressures. The investigated properties have been established through both full-potential-linearized augmented plane wave (FP-LAPW) and plane-wave pseudopotential (PW-PP) approaches, in conjunction with the generalized gradient approximation (GGA). Our investigations validate that the LaC2 crystal has a mechanical and dynamical stability under normal conditions. The generalised mechanical stability criteria applied to compressed LaC2, suggest that the compound remains stable for pressures below 18.30 GPa. The evaluated superconducting critical temperature Tc and the electron–phonon coupling parameter λ at zero pressure are found to be in excellent concordance with the experimental data. Furthermore, at elevated pressures, Tc and λ are predicted to decrease and the normalised specific heat jump remains unchanged.

Lithium-based perovskites materials for photovoltaic solar cell and protective rays window applications: a first-principle calculations

Perovskites are the key enabler materials for the solar cell applications in the achievement of high performance and low production costs. In this article, the structural, mechanical, electronic, and optical properties of rubidium-based cubic nature perovskite LiHfO3 and LiZnO3 are investigated. These properties are investigated using density-functional theory with the aid of CASTEP software by introducing ultrasoft pseudo-potential plane-wave (USPPPW) and GG-approximation-PB-Ernzerhof exchange–correlation functionals. It is investigated that the proposed compounds exhibit stable cubic phase and meet the criteria of mechanical stability by the estimated elastic properties. Also, according to Pugh's criterion, it is noted that LiHfO3 is ductile and LiZnO3 is brittle. Furthermore, the electronic band structure investigation of LiHfO3 and LiZnO3 shows that they have indirect bandgap (BG). Moreover, the BG analysis of the proposed materials shows that these are easily accessible. Also, the results for partial density of states (DOS) and total DOS confirm the degree of a localized electron in the distinct band. In addition, the optical transitions in the compounds are examined by fitting the damping ratio for the notional dielectric functions scaling to the appropriate peaks. At absolute zero temperature, the materials are observed as semiconductors. Therefore, it is evident from the analysis that the proposed compounds are excellent candidates for solar cells and protective rays applications.

Ab-initio probe into the elastic, mechanical and thermo-mechanical properties of CsSe binary compound

First principles computational simulations were performed using Quantum ESPRESSO package within the framework of Density Functional Theory (DFT) in order to analyze the structural, elastic and thermo-mechanical conditions of one of the Caesium monochalcogenides (CsSe) in a bid to fill some of the theoretical information gaps in this material. The obtained optimized lattice parameter of 7.432[Formula: see text]Å from well convergence tests agreed reasonably with results from other previous theoretical works. Three independent elastic constants ([Formula: see text], [Formula: see text] and [Formula: see text]) and other mechanical indices for this cubic system were determined by fitting stress–stain relationship data via Voigt–Reuss–Hill approximation (VRHA) of Quantum ESPRESSO incorporated Thermo_pw code. CsSe is elastically and mechanically stable since the elastic constants fulfilled the Born–Huang cubic mechanical stability criteria of forms: [Formula: see text]; [Formula: see text] and [Formula: see text]. The resistiveness of CsSe to recoverable deformation under applied force was studied via elastic moduli: bulk (B), Young (E) and shear (G) moduli. Pugh’s ratio ([Formula: see text]) [Formula: see text] depicted ductility and the positive value of Cauchy pressure: [Formula: see text][Formula: see text]GPa further confirmed the ductile nature of this system. Poisson ratio, [Formula: see text], within the domain of 0.25 and 0.42, classified the compound as a metallic bonded specie. One of the three estimated sound velocity variants for the system best predicted the average Debye temperature. Some other important structural and thermo-mechanical-related parameters such as Zener anisotropy, elastic constants based Debye temperature, average speed of sound, Lame’s constants, Kleinmann parameters, hardness (micro and macro) and melting temperature were determined. The interdependencies of these obtained parameters were established and reported.

Structural, Mechanical, Electronic, Optical, and Thermodynamic Properties of New Oxychalcogenide A2O2B2Se3 (A = Sr, Ba; B = Bi, Sb) Compounds: A First-Principles Study

The structural, mechanical, electronic, and optical characteristics of Alkali chalcogenide and oxychalcogenides, i.e., A2O2B2Se3 (A = Sr, Ba; B = Bi, Sb), were investigated using density functional theory (DFT). After full relaxation, the obtained structural parameters are in good agreement with the experimental parameters. Furthermore, the calculated elastic stiffness Cij shows that all of the studied compounds followed the mechanical stability criteria. Ductility for these compounds was analyzed by calculating Pugh’s ratio; we classified the Sr2O2Bi2Se3, Sr2O2Sb2Se3, and Ba2O2Bi2Se3 as ductile, and the Ba2O2Sb2Se3 as brittle. The Debye temperature and acoustic velocity were estimated. In addition, electronic and chemical bonding properties were studied from the analysis of the band structure and density of state. The main features of the valence and conduction bands were analyzed from the partial density of states. Electronic band structures are mainly contributed to by Se-4p and Bi-6p/Sb-5p states. Direct band gaps are 0.90, 0.47, and 0.73 eV for Sr2O2Bi2Se3, Sr2O2Sb2Se3, and Ba2O2Sb2Se3, respectively. The Ba2O2Bi2Se3 compound has an indirect band gap of 1.12 eV. Furthermore, we interpreted and quantified the optical properties, including the dielectric function, absorption coefficient, optical reflectivity, and refractive index. From the reflectivity spectra, we can state that these compounds will be useful for optical applications.

Insight into the structural, optoelectronic, and thermoelectric properties of Fe2HfSi Heusler by DFT investigation.

At high pressure, the pressure dependencies of the structural, electronic, optical, and thermoelectric properties of Fe2HfSi Heusler were calculated using the FP-LAPW method within the framework of the density functional theory. The calculations were carried out using the modified Becke-Johnson (mBJ) scheme. Our calculations showed that the Born mechanical stability criteria confirmed the mechanical stability in the cubic phase. Further, through Poisson and Pugh's ratios critical limits, the findings of the ductile strength were computed. At a pressure of 0 GPa, the indirect nature of the material may be deduced from the electronic band structures of Fe2HfSi as well as the estimations for its density of states. Under pressure, the real and imaginary dielectric function responses, optical conductivity, absorption coefficient, energy loss function, refractive index, reflectivity, and extinction coefficient were computed in the 0-12 eV range. Using semi-classical Boltzmann theory, a thermal response is also studied. As the pressure rises, the Seebeck coefficient decreases, while the electrical conductivity rises. The figure of merit (ZT) and Seebeck coefficients were determined at temperatures of 300 K, 600 K, 900 K, and 1200 K in order to better understand the thermoelectric properties of a material at these different temperatures. Despite the fact that the ideal Seebeck coefficient for Fe2HfSi was discovered at 300 K and was determined to be superior to that reported previously. Materials with a thermoelectric reaction has been shown to be suitable for reusing waste heat in systems. As a result, Fe2HfSi functional material may aid in the development of new energy harvesting and optoelectronic technologies.

A comparative study of the structural, elastic, thermophysical, and optoelectronic properties of CaZn2X2 (X = N, P, As) semiconductors via ab-initio approach

We present a detailed density functional theory (DFT) based calculations of the structural, elastic, lattice dynamical, thermophysical, and optoelectronic properties of ternary semiconductors CaZn2X2 (X = N, P, As) in this paper. The obtained lattice parameters are in excellent agreement with the experimental values and other theoretical findings. The elastic constants are calculated. The computed elastic constants satisfy the mechanical stability criteria. Moreover, large numbers of thermophysical parameters of these compounds are estimated, including the Debye temperature, average sound velocity, melting temperature, heat capacity, lattice thermal conductivity, etc. The comprehensive analysis of the elastic constants and moduli show that CaZn2X2 (X = N, P, As) compounds possess reasonably good machinability, strongly X-dependent Debye temperature and high Vickers hardness. The phonon dispersion curves and phonon density of states are investigated for the first time for the compounds CaZn2P2 and CaZn2As2. It is observed from the phonon dispersion curves that the bulk CaZn2X2 (X = N, P, As) compounds are dynamically stable in the ground state. Electronic properties have been studied through the band structures and electronic energy density of states. HSE06 (hybrid) functional is used to estimate the band gaps accurately. The electronic band structures show that CaZn2N2 and CaZn2As2 possess direct band gaps while the compound CaZn2P2 has an indirect band gap. The bonding characters of CaZn2X2 (X = N, P, As) compounds are investigated. We have thoroughly discussed the reflectivity, absorption coefficient, refractive index, dielectric function, optical conductivity and loss function of these semiconductors. The optical absorption, reflectivity spectra and the refractive index of CaZn2X2 (X = N, P, As) show that they hold promise to be used in optoelectronic devices.