Showing papers on "Debye model published in 2022"

A review of band structure and material properties of transparent conducting and semiconducting oxides: Ga2O3, Al2O3, In2O3, ZnO, SnO2, CdO, NiO, CuO, and Sc2O3

Abstract: This Review highlights basic and transition metal conducting and semiconducting oxides. We discuss their material and electronic properties with an emphasis on the crystal, electronic, and band structures. The goal of this Review is to present a current compilation of material properties and to summarize possible uses and advantages in device applications. We discuss Ga2O3, Al2O3, In2O3, SnO2, ZnO, CdO, NiO, CuO, and Sc2O3. We outline the crystal structure of the oxides, and we present lattice parameters of the stable phases and a discussion of the metastable polymorphs. We highlight electrical properties such as bandgap energy, carrier mobility, effective carrier masses, dielectric constants, and electrical breakdown field. Based on literature availability, we review the temperature dependence of properties such as bandgap energy and carrier mobility among the oxides. Infrared and Raman modes are presented and discussed for each oxide providing insight into the phonon properties. The phonon properties also provide an explanation as to why some of the oxide parameters experience limitations due to phonon scattering such as carrier mobility. Thermal properties of interest include the coefficient of thermal expansion, Debye temperature, thermal diffusivity, specific heat, and thermal conductivity. Anisotropy is evident in the non-cubic oxides, and its impact on bandgap energy, carrier mobility, thermal conductivity, coefficient of thermal expansion, phonon modes, and carrier effective mass is discussed. Alloys, such as AlGaO, InGaO, (Al xIn yGa1− x− y)2O3, ZnGa2O4, ITO, and ScGaO, were included where relevant as they have the potential to allow for the improvement and alteration of certain properties. This Review provides a fundamental material perspective on the application space of semiconducting oxide-based devices in a variety of electronic and optoelectronic applications.

First-principles calculations to investigate structural, elastic, electronic, thermodynamic, and thermoelectric properties of CaPd3B4O12 (B = Ti, V) perovskite

Abstract: This study has explored numerous physical properties of CaPd$_3$Ti$_4$O$_{1}$2 (CPTO) and CaPd$_3$V$_4$O$_{12}$ (CPVO) quadruple perovskites employing the density functional theory (DFT) method. The mechanical permanence of these two compounds was observed by the Born stability criteria as well. The band structure of CPTO reveals a 0.88 and 0.46 eV direct narrow band gap while using GGA-mBJ and GGA-PBE potentials, respectively, which is an indication of its fascinating semiconducting nature. The calculated partial density of states indicates the strong hybridization between Pd-4d and O-2p orbital electrons for CPTO, whereas Pd-4d and V-3d-O-2p for CPVO. The study of the chemical bonding nature and electronic charge distribution graph reveals the coexistence of covalent O-V/Pd bonds, ionic O-Ti/Ca bonds, as well as metallic Ti/V-Ti/V bonding for both compounds. The Fermi surface of CPVO ensures a kind of hole as well as electron faces simultaneously, indicating the multifarious band characteristic. The prediction of the static real dielectric function (optical property) of CPTO at zero energy implies its promising dielectric nature. The photoconductivity and absorption coefficient of CPBO display good qualitative compliance with the consequences of band structure computations. The calculated thermodynamic properties manifest the thermodynamical stability for CPBO, whereas phonon dispersions of CPVO exhibit stable phonon dispersion in contrast to slightly unstable phonon dispersion of CPTO. The predicted Debye temperature ($\theta_D$) has been utilized to correlate its topical features including thermoelectric behaviors. The studied thermoelectric transport properties of CPTO yielded the Seebeck coefficient (186 V/K), power factor (11.9 Wcm$^{-1}$K$^{-2}$), and figure of merit (ZT) value of about 0.8 at 800 K, indicating that this material could be a promising candidate for thermoelectric applications.

Anisotropic Elastic and Thermal Properties of M2InX (M = Ti, Zr and X = C, N) Phases: A First-Principles Calculation

Abstract: First-principles calculations were used to estimate the anisotropic elastic and thermal properties of Ti2lnX (X = C, N) and Zr2lnX (X = C, N) M2AX phases. The crystals’ elastic properties were computed using the Voigt-Reuss-Hill approximation. Firstly, the material’s elastic anisotropy was explored, and its mechanical stability was assessed. According to the findings, Ti2lnC, Ti2lnN, Zr2lnC, and Zr2lnN are all brittle materials. Secondly, the elasticity of Ti2lnX (X = C, N) and Zr2lnX (X = C, N) M2AX phase are anisotropic, and the elasticity of Ti2lnX (X = C, N) and Zr2lnX (X = C, N) systems are different; the order of anisotropy is Ti2lnN > Ti2lnC, Zr2lnN > Zr2lnC. Finally, the elastic constants and moduli were used to determine the Debye temperature and sound velocity. Ti2lnC has the maximum Debye temperature and sound velocity, and Zr2lnN had the lowest Debye temperature and sound velocity. At the same time, Ti2lnC had the highest thermal conductivity.

First-principles insights into the electronic, optical, mechanical, and thermodynamic properties of lead-free cubic ABO3 [A = Ba, Ca, Sr; B = Ce, Ti, Zr] perovskites

Abstract: A comparative study on mechanical, thermodynamic, electronic, and optical properties has been performed on various compounds having an ABO3, where A = Ba, Ca, Sr and B = Ce, Ti, Zr, perovskite structure using first-principles calculations. These materials’ properties have been thoroughly investigated for their ground states under the same computational parameters. The computed lattice parameters in the ground state agreed with other theoretical studies. Elastic moduli, ductility or brittleness, elastic anisotropy, mechanical stability, and stiffness of solid materials are studied. Enthalpy (H), entropy (S), and free energy (F) were reported from the vibrational properties of the materials. The temperature-dependent heat capacity and Debye temperature are investigated. The electronic band structure as a function of energy, of different perovskite structures at the ground state, is also studied. From this study, the ABO3 perovskite has emerged as the most promising material for applications in optoelectronics, photonics, and mechanical and thermoelectric devices.

First-principles insights into mechanical, optoelectronic, and thermo-physical properties of transition metal dichalcogenides ZrX2 (X = S, Se, and Te)

Abstract: Transition metal dichalcogenides (TMDCs) belong to technologically important compounds. We have explored the structural, elastic, bonding, optoelectronic, and some thermo-physical properties of ZrX2 (X = S, Se, and Te) TMDCs in detail via the ab initio technique in this work. Elastic anisotropy indices, atomic bonding character, optoelectronic properties, and thermo-physical parameters, including melting temperature and minimum phonon thermal conductivity, are investigated for the first time. All the TMDCs under investigation possess significant elastic anisotropy and layered structural features. ZrX2 (X = S, Se, and Te) compounds are fairly machinable, and ZrS2 and ZrSe2 are moderately hard. ZrTe2, on the other hand, is significantly softer. Both covalent and ionic bondings contribute in the crystals. Electronic band structure calculations display semiconducting behavior for ZrS2 and ZrSe2 and metallic behavior for ZrTe2. Energy dependent optoelectronic parameters exhibit good correspondence with the underlying electronic energy density of state features. ZrX2 (X = S, Se, and Te) compounds absorb ultraviolet radiation effectively. The reflectivity spectrum, R(ω), remains over 50% in the energy range from 0 to ∼20 eV for ZrTe2. Therefore, this TMDC has a wide band and nonselective high reflectivity and can be used as an efficient reflector to reduce solar heating. The Debye temperature, melting point, and minimum phonon thermal conductivity of the compounds under study are low and show excellent correspondence with each other and also with the theoretically predicted elastic and bonding characteristics.

A DFT insight into the mechanical, electronic and thermodynamic properties of (TiZrHf)C medium-entropy carbide ceramic

Abstract: Recently, a novel medium-entropy transition-metal (TM) carbide (TiZrHf)C has been synthesized with high flexural strength. However, the underlying mechanisms responsible for its outstanding properties are not well understood. Herein, the crystal, mechanical, electronic and thermodynamic properties of (TiZrHf)C are systematically investigated by the first-principles density functional theory (DFT) calculations. The obtained results reveal that the (TiZrHf)C structure is stable in the pressure range of 0 GPa–100 GPa. The elemental random distribution and atomic size difference give rise to local lattice distortion. The lattice distortion, elastic moduli, anisotropy, sound velocity and Debye temperature of (TiZrHf)C increase with the increase of pressure. Electron structure analysis shows that (TiZrHf)C has metallic, ionic and covalent bonding features. The thermodynamic calculation reveals that the thermal expansion and heat capacity of (TiZrHf)C are consistent with that of binary carbides, implying (TiZrHf)C can be used for high temperature applications like traditional carbides.

First Principles Investigation of Binary Chromium Carbides Cr7C3, Cr3C2 and Cr23C6: Electronic Structures, Mechanical Properties and Thermodynamic Properties under Pressure

Abstract: Binary chromium carbides display excellent wear resistance, extreme stiffness and oxidation resistance under high temperature. The influence of applied pressure on electronic structure, elastic behavior, Debye temperature and hardness of Cr7C3, Cr3C2 and Cr23C6 have been investigated by the density functional theory (DFT) method. The results reveal that lattice parameters and formation enthalpy display an inverse relationship with applied pressure, and Cr3C2 exhibited optimal structural stability. Moreover, Cr-C orbital hybridization tends to be stronger due to the decreased partial density of states (PDOS) of the Cr atom. The difference in electronic distribution of binary carbides has also been investigated, which confirmed that overall orbital hybridization and covalent characteristics has been enhanced. The theoretical hardness was elevated according to the higher bond strength and bond density. In accordance with structural stability data, Cr3C2 has shown maximum theoretical hardness. Furthermore, the anisotropic nature of hardness has been evaluated with external pressure. Cr3C2, and the highest isotropic hardness behavior along with an increase in hardness values with increasing pressure has been observed. In addition, the variation in Debye temperatures of binary chromium carbides under applied pressure has also been predicted. The results provide a theoretical insight into electronic, mechanical and thermodynamic behavior of three binary chromium carbides and show the potential of these novel carbides in a wide range of applications.

Insights of electronic structures, mechanical properties and thermal conductivities of TM5SiB2 (TM=V, Nb, and Ta) MAB phases

Abstract: ABSTRACT The electronic, elastic, and thermal properties of TM5SiB2 (TM = V, Nb, and Ta) MAB phases are calculated herein using first-principles calculations. The obtained electronic structures show that there are p-d hybridizations between B, Si, and TM atoms, and TM-B and TM-Si bonds are formed by the electrons transfer between TM and B, TM and Si. Elastic Modulus and elastic Anisotropy Index, three-dimensional surface construction, and two-dimensional projection are used to discuss the elastic anisotropy, and the results show that these TM5SiB2 MAB phases are anisotropic in elastic modulus with the order of V5SiB2 > Nb5SiB2 > Ta5SiB2. Besides, the Debye temperature and sound velocity of these TM5SiB2 are also analyzed. The thermal conductivities are obtained, and the thermal conductivity is also anisotropic and in the same order as elastic modulus.

Effects of temperature and pressure on the mechanical and thermodynamic properties of high-boride WB4 from first-principles predictions

Abstract: Tungsten borides with high boron content are widely used in high temperature and high pressure conditions. In this work, the first-principles calculations were employed to investigate the influence of pressure and temperature on the structure, mechanical properties and thermodynamic properties of hp10-WB4. The results show that hp10-WB4 is dynamically and thermodynamically stable over a range of temperatures (0–800 K) and pressures (0–35 GPa). In general, the elastic constants and modulus are improved at the appropriate pressure state. The single crystal tensile simulations in the ground state show that hp10-WB4 has good strength. And the lattice parameters, crystal structure stability, electronic properties, heat capacity, thermal expansion coefficient α, Debye temperature θD and Grüneisen parameter γ are also investigated at 0–35 GPa pressure and 0–800 K temperature. The thermal expansion coefficient is sensitive to temperature and pressure. The Debye temperature and Grüneisen parameters show the opposite trend, and the effect of temperature and pressure on them is slight.

A comparative DFT exploration on M- and A-site double transition metal MAX phase, Ti3ZnC2

Abstract: The combination of ceramic and metallic properties of the MAX phases makes them attractive for numerous technological applications. The very recent experimental synthesis of the Zn-based MAX phase Ti3ZnC2 is an important addition to the MAX phase family as it further expands the diversity of physical characteristics of this family. Here we have employed density functional theory (DFT) calculations to investigate the structural, electronic, mechanical, lattice dynamic and thermal properties of Ti3ZnC2 for comparison with existing Ti3AC2 phases. Additional transition metal Zn at A-site in newly synthesized Ti3ZnC2 reduces most of the elastic constants and moduli as well as the Debye temperature and thermal conductivity. All the Ti3AC2 phases have the potential to be etched into 2D MXenes with great possibility for Ti3ZnC2. Ti3ZnC2 is highly anisotropic in the Ti3AC2 MAX phase family.

New Insights into the Piezoelectric, Thermodynamic and Thermoelectric Properties of Lead-Free Ferroelectric Perovskite Na0.5Bi0.5TiO3 from Ab initio Calculations

Abstract: Ab initio DFT calculations have been performed to investigate a complete set of structural, electronic, elastic, piezoelectric, thermodynamic and thermoelectric properties of lead-free perovskite Na0.5Bi0.5TiO3 (NBT) crystalizes in rhombohedral (R3c), tetragonal (P4bm) and cubic (Pm3̅m) phases. The lattice stabilities in Na0.5Bi0.5TiO3 crystals are studied from the formation energy and phonon dispersions. Electronic band profiles obtained using new KTBmBJ+so potential reveal that R3c, P4bm and Pm3̅m phases of NBT are indirect band gap semiconductors with energy values of ~ 3.29, 3.05 and 3.09 eV, respectively. Analysis of the calculated elastic constants (Cij) indicates that NBT systems are elastically stable. Ferroelectric tetragonal NBT crystal shows relatively high piezoelectric coefficients [d15 = 101.0 pC/N, d31 = 51.3 pC/N and d33 = 81.1 pC/N], compared to the rhombohedral system [d15 = 96.4 pC/N, d31 = 8.93 pC/N and d33 = 21.2 pC/N and d22 = 21.2 pC/N]. Thermodynamic quantities for rhombohedral NBT compound were calculated using the quasi-harmonic Debye model. Thermoelectricity in terms of electrical conductivity σ/τ, thermal conductivity κ/τ, Seebeck coefficient S, figure of merit ZT and thermo power for NBT crystals were examined using BoltzTraP2 code. P4bm-NBT structure showed a largest magnitude of S ~ 201.42 µV/K (at T = 500 K), following by Pm3̅m ~ 173.6 µV/K (800 K) and R3c ~ 158.6 µV/K (100 K). ZT maximized to high values ~ 2.76 (at 700 K), 2.16 (900 K) and 1.96 (400 K) for P4bm, Pm3̅m and R3c structures, respectively. Na0.5Bi0.5TiO3 (NBT) compounds could be a promising candidate for use in manufacturing high-performance piezoelectric devices and developing high-power thermoelectric generators.

Study of lead-free vacancy ordered double perovskites Cs2TeX6 (X = Cl, Br, I) for solar cells, and renewable energy

Abstract: Herein, the electronic, optical, mechanical, and transport properties of a double perovskites Cs2TeX6 (X = Cl, Br, I) are explored with the focus on solar cell and thermoelectric applications by the density functional theory (DFT). The feasibility of structural, thermodynamic, and elastic stabilities is arbitrated by a tolerance factor, formation energy, and elastic constant, respectively. Further, the Poisson and Pugh’s ratio display the ductile behavior of studied compounds. From the electronic properties analysis, it is revealed that the bandgap decreases by changing Cl with Br, and I from 2.67 eV to 2.52 eV and 1.73 eV, respectively which in results tune the optical properties from visible to infrared region. The shifting of maximum absorption from visible to infrared region makes them promising materials for solar cell and remote sensing devices. Moreover, various optical parameters including refractive index, reflectivity, and optical loss were also reported. Additionally, the transport characteristics were analyzed by electrical, thermal conductivities, and figure of merit (ZT) versus temperature and chemical potential effect. The ZT increases from Cl to I substitution. At the end, the thermodynamic behavior studied by specific heat capacity, Debye temperature and Hall coefficient was presented. All these characteristics have demonstrated that our studied materials are excellent choice for probing solar cell and renewable energy applications.

Investigations of martensitic, thermodynamics, elastic, electronic, magnetic, thermal and thermoelectric properties of Co2FeZ Heusler alloys (Z=Si; Ge; Al; Ga): a first principle study

Abstract: In this study, the first-principle calculations using FPLAPW based on density functional theory, have been employed to examine and deeply understand the martensitic, thermodynamics, elastic, electronic, magnetic, thermal and thermoelectric properties of full-Heusler Co2FeZ in the L21 phase. The fundamental physical properties such as lattice parameter, bulk modulus, anisotropy factor, Poisson’s ratio, elastic constants, and Young’s modulus are obtained and then compared with the theoretical and experimental results. Subsequently, Debye temperature, heat capacity, entropy, thermal expansion coefficient and Grüneisen parameter are also evaluated over the temperature range of 0–1500 K. The band structures and the density of states curves are presented for all alloys intended to interpret the electronic and magnetic stabilities of Co2FeZ Heusler compounds in the L21 phase. Additionally, the Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and power factor of these systems have been studied as a function of the temperature and chemical potential. GRAPHICAL ABSTRACT

Elastic anisotropy and thermal properties of Zr-Al-N ternary nitrides using first-principles explorations

Abstract: First-principles calculations based on density functional theory (DFT) were employed to explore the anisotropies in elastic and thermal properties of six Zr-Al-N ternary nitrides (Zr2AlN, Zr5Al3N, ZrAlN2, Zr3AlN4, ZrAl3N4 and Zr3AlN). The single-crystal elastic constants and poly-crystalline elastic moduli were acquired by using Voigt-Reuss-Hill approximations. The elastic anisotropies of the above six Zr-Al-N ternary nitrides were characterized by a three-dimensional (3D) surface constructions and two-dimensional (2D) plane projections. The elastic modulus anisotropy is in the order of ZrAlN2 > Zr3AlN > ZrAl3N4 > Zr3AlN4 >Zr2AlN > Zr5Al3N. Furthermore, these six Zr-Al-N ternary nitrides have the hardness ranging from 12.7 to 18.7 GPa. Moreover, these six ternary nitrides all meet the brittleness criteria in terms of Poisson's ratio, GH/BH and Cauchy pressure. Finally, the sound velocities, Debye temperature, thermal conductivity and their anisotropies of these Zr-Al-N ternary nitrides are discussed, showing that the sound velocities and Debye temperature are anisotropic in the [001] and [100] directions.