Debye Temperature Research Articles

Computational study of Rubidium-Rb based cubic Rb2TlCoF6 double perovskite material for photocatalytic water degradation applications: A DFT investigations

The fascinating characteristics, such as straightforward and stable crystal structure, and double perovskites are currently popular materials for applications in renewable energy. In our study, we applied CASTEP and DFT, called density functional theory, to theoretically investigate the mechanical, optical, and thermoelectric characteristics of cubic Rb2TlCoF6. Calculations of the compound Rb2TlCoF6's structural, electrical, optical, mechanical, and thermodynamic properties are made using the GGA-PBE exchange correlational functional and the Fm3m with space group no.225 vol and compound lattice constant are 9.08 Å and 748.613 Å3, respectively. For Rb2TlCoF6, the measured energy band gaps are 1.45 eV. The mechanical and elastic constants are calculated to confirm the ductile properties of Rb2TlCoF6. The brittle characteristics have been verified using Passion and Pugh's ratios, which are 1.67 and 0.25, according to elastic constants. Vickers compound hardness Hv and anisotropy factor “A” are 4.19 and 0.77, respectively. The compounds' optical characteristics reveal significant conductivity and absorption. The compound exhibits high-efficiency photocatalytic activity based on its optical characteristics. Based on mechanical stability, such as Debye temperature, melting temperature, minimum thermal conductivity, average sound velocity, free energy, and other variables, the thermodynamic and structural stabilities are calculated. These materials controlled electrical and other properties make them potentially useful in photocatalytic applications. According to the outcomes, Rb2TlCoF6 is appropriate for photocatalytic water-splitting applications and water deterioration.

Study of thermodynamic properties and elastic constants of cubic boron nitride by statistical moment method

The statistical moment method has been applied to investigate temperature effects on the thermodynamic and elastic properties of the cubic boron nitride (cBN). The analytical expressions of thermal-induced atomic displacement, the mean-square displacement, elastic constants (Young’s modulus, bulk modulus, shear modulus, and longitudinal-wave elastic constant), and the bulk and longitudinal sound velocities of cBN compound have been derived. Our theoretical calculations are compared with previous experiments and computations showing reasonable agreement. We have shown that while the mechanical strength and Debye temperature of the cBN material are slightly reduced as temperature rises, the mean-square displacement function increases rapidly. The noticeable difference in mean-square displacements of B isotopes is observed at low temperature, and the disparity diminishes gradually at high temperatures. The calculations of the present work can be used as an appropriate reference for the future experiments.

Study of multiscale mechanical properties of Al-Pd-Mn quasicrystals

Based on the quantum mechanics and molecular mechanics scales, the elastic and tensile mechanical properties of Al-Pd-Mn quasicrystals (QCs) are investigated by utilizing the first-principles and molecular dynamics (MD) methods. The density functional theory (DFT) is adopted to obtain all elastic constants, stability, elastic modulus, Poisson's ratio, anisotropy, Debye temperature of Al57Pd16Mn3 QCs. Simultaneously, the MD simulations are conducted to analyze the influence of temperature and strain rate on the stress-strain curves, atomic structures, and deformation mechanism. The results indicate that Al57Pd16Mn3 QCs are stable orthogonal structures and satisfy the Cauchy conditions. Additionally, the mechanical properties of Al-Pd-Mn QCs obtained by the first-principles are consistent with the MD and experimental results. The elastic properties of Al57Pd16Mn3 QCs are approximately isotropic. The elastic modulus and ultimate tensile strength of Al57Pd16Mn3 QCs always decrease with increasing temperature. An increase in the strain rate results in a negligible change in the elastic modulus but in a noticeable enhancement in the ultimate tensile strength and strain. The current results could provide essential theoretical insights for studying the mechanical properties of QCs, and extend the scope of multi-scale study in the field of QCs at microcosmic scale as well.

Composition, Temperature, and Size Regulation of Refractive Index in Ternary Group-Ⅲ Nitride Alloys: a Bond Relaxation Investigation

Abstract The physical origins of composition-, temperature-, and size-motivated changes in refractive index in crystals have long been a puzzle. Combining the bond-order-length-strength theory, local bond average approach, and core-shell structural model, we investigated the refractive indexes in dependencies of composition, temperature, and size for the ternary wurtzite group-Ⅲ nitride alloys. The theoretical reproduction of the observations disclosed that (ⅰ) the doping of small atoms caused the contraction in bond length, the strengthening in bond energy, and the decrease of refractive index, whereas the doping of large atoms led to an elongation of bond length, a weakening of bond energy, and an increase of refractive index; (ⅱ) the refractive index is inversely proportional to the cohesive energy and the cube of the Debye temperature; and (ⅲ) with the gradual decrease in solid size, the coordination number lowers, the bond length contracts, the bond energy gains, the surface-to-volume ratio rises, and the refractive index decreases. The proposed formulation not only shows an in-depth comprehension of the physical essence of the stimuli impact on the refractive index but also is expected to be conducive to the exploitation, optimization, and operation of the new-type photonic, piezoelectric, and pyroelectric nanometer devices for the ternary wurtzite alloys.

First‐Principles Calculations to Investigate the Structural, Mechanical, Electronic, Optical and Thermal Properties of Disilicides Materials UT2Si2 (T = Ru, Rh, and Pd)

Different physical features of UT2Si2 (T = Ru, Rh, Pd) are investigated using ab initio methods. The examined lattice parameters are closely aligned with the experimental data. The negative cohesive energy ensures the chemical stability of the UT2Si2 (T = Ru, Rh, Pd). The mechanical stability of UT2Si2 (T = Ru, Rh, Pd) is ensured from the positive elastic constants. Very large bulk and Young's moduli of URu2Si2, and URh2Si2 ensures their high resistance to volume and longitudinal deformation. Whereas the lower Young's modulus (E) for UPd2Si2 suggests its heightened capacity to resist thermal shock resistance. The high machinable index of UPd2Si2 compared to URu2Si2 and URh2Si2 confirm its more damage‐tolerant and high elastic behavior and probable industrial applications. All the phases exhibit elastic anisotropy and ductile nature. Metallic features as well as mixture of covalent and ionic bonding are observed from electronic properties. Furthermore, the investigation on optical properties suggests the potential use of UT2Si2 (T = Ru, Rh, Pd) in anti‐reflection coatings, UV detectors, and optoelectronic devices due to their notable peaks in the UV energy range. The thermodynamic parameters such as Debye temperature as well as minimum thermal conductivity indicate the potential utility of these compounds in thermal barrier coating materials.

Thermophysical Investigation of Multiform NiO Nanowalls@carbon Foam/1-Octadecanol Composite Phase Change Materials for Thermal Management.

Multiform NiO nanowalls with a high specific surface area were constructed in situ on carbon foam (CF) to construct NiO@CF/OD composite phase change materials (CPCMs). The synthesis mechanism, microstructures, thermal management capability, and photothermal conversion of NiO@CF/OD CPCMs were systematically studied. Additionally, the collaborative enhancement effects of CF and multiform NiO nanowalls on the thermal properties of OD PCMs were also investigated. NiO@CF not only maintains the porous 3D network structure of CF, but also effectively prevents the aggregation of NiO nanosheets. The chemical structures of NiO@CF/OD CPCMs were analyzed using XRD and FTIR spectroscopy. When combined with CF and NiO nanosheets, OD has high compatibility with NiO@CF. The thermal conductivity of NiO@CF/OD-L CPCMs was 1.12 W/m·K, which is 366.7% higher than that of OD. The improvement in thermal conductivity of CPCMs was theoretically analyzed according to the Debye model. NiO@CF/OD-L CPCMs have a photothermal conversion efficiency up to 77.6%. This article provided a theoretical basis for the optimal design and performance prediction of thermal storage materials and systems.

Study of electronic, mechanical, optical, and thermoelectric properties of stable double perovskites Cs2K(Ga/In)I6 for solar cells renewable energy

Double perovskites are exceptional materials for thermoelectric and optoelectronic applications in pursuing green energy. In this study, a comprehensive analysis of Cs2K(Ga/In)I6 has been conducted, focusing on its mechanical, electronic, optical, and thermoelectric properties by using wien2k, BoltzTraP, ShengBTE, and Phonopy codes. The stability of these compounds has been ensured by considering the tolerance factor, formation energy, phonon spectra, and elastic constants. The elastic and thermophysical properties, including ductility, anisotropy, Debye temperature, and melting temperature, are reported to be noteworthy. The band gaps of Cs2K(Ga/In)I6, measured to be 1.92 and 2.08 eV, indicate the presence of absorption bands in both the visible and ultraviolet regions. Significant absorbance, polarization, low optical reflectivity, and energy loss have been discussed in relation to photovoltaic applications. In addition, the transport characteristics are examined by analyzing the Seebeck coefficient and thermal and electrical conductivities. Due to their high figure of merit and exceptionally low lattice thermal conductivity at room temperature, these materials are highly recommended for thermoelectric generators.

On ablation characteristics based on two-temperature model involving a multivariate lattice heat capacity by ultrashort laser-irradiated in zirconia

To explore the mechanism of material removal, this paper conducts a systematic study on picosecond laser processing of zirconia by using both theory and experiment. Comparing the multivariate lattice heat capacity of the Einstein and Debye models, two-temperature model (TTM) is developed to improve the accuracy of the temperature field. Then, to verify the effectiveness of TTM proposed, ablation experiments are performed by single-pulse picosecond laser on zirconia at different laser energy density. The results show that the measured craters profiles are well agree with the simulated melting/vaporization temperature distribution. Micro-morphology is significantly affected by phase transition induced by temperature rise. Moreover, the results confirmed that increased temperature can lead to transition in zirconia crystal structure and oxygen vacancies. Finally, the effect of coupling temperature variations on the elemental and physical phase variations are focused to investigate, which can help to optimize the processing quality due to crystalline phase transitions. This study provides guidance for optimizing picosecond laser processing of zirconia.

Enhanced optoelectronic and thermoelectric properties of half Heusler compounds KXSb (X = Be, Mg, Ca and Sr): A first principle study

In the present paper, structural, electronic, elastic, thermodynamic, optical, and thermoelectric properties of h-H alloys KXSb (X = Be, Mg, Ca, and Sr) are investigated for the first time. These properties were explored using quantum mechanical model – the density functional theory (DFT) with both GGA-PBE and TB-mBJ exchange-correlation functional. The Boltzmann transport equations and the Full Potential Linearized Augmented Plane wave (FP-LAPW) approach, as built into the WIEN2k code, are used to investigate these properties. The band structures and density of states (DOS) are also studied. The half-Heusler compounds show semiconductor properties with both the GGA and mBJ methods, while the KBeSb alloy exhibits metallic nature under the GGA-PBE approach. The elastic and thermo dynamical properties were also investigated, and the results revealed that the compounds are mechanically and thermally stable. The observed high Debye temperature (ϴD) implies that the alloy is harder and possesses a significant Debye sound velocity. The current paper highlights the optical and thermoelectric applications of the alloys. At 900 K, KCaSb exhibits maximum power factors of 8.83 × 1011 (W/mK2s) with the GGA-PBE method and 8.19 × 1011 (W/mK2s) with the TB-mBJ approach.

Phonons in stringlet-land and the boson peak

Solid materials that deviate from the harmonic crystal paradigm exhibit characteristic anomalies in the specific heat and vibrational density of states (VDOS) with respect to Debye's theory predictions. The boson peak (BP), a low-frequency excess in the VDOS over Debye lawg(ω)∝ω2, is certainly the most famous among them; nevertheless, its origin is still subject of fierce debate. Recent simulation works provided strong evidence that localized one-dimensional string-like excitations (stringlets) might be the microscopic origin of the BP. In this work, we study the dynamics of acoustic phonons interacting with a bath of vibrating 1D stringlets with exponentially distributed size, as observed in simulations. We show that stringlets strongly renormalize the phonon propagator and naturally induce a BP anomaly in the VDOS, corresponding to the emergence of a dispersionless BP flat mode. Additionally, phonon-stringlet interactions produce a strong enhancement of sound attenuation and a dip in the speed of sound near the BP frequency, consistent with experimental and simulation data. The qualitative trends of the BP frequency and intensity are predicted within the model and shown to be in good agreement with previous observations. In summary, our results substantiate with a simple theoretical model the recent simulation results by Hu and Tanaka claiming the origin of the BP from stringlet dynamics.

Ab initio investigation of the structural, mechanical, electronic, thermodynamic, and optical properties of V2FeNiGe2 and Hf2FeNiSb2 double half-Heusler compounds

In the present work, using ab initio density-functional theory methods based on the Quantum ESPRESSO package, we have investigated the structural, elastic, electronic, and optical properties of 18-electron V2FeNiGe2 and Hf2FeNiSb2 double half-Heusler alloys. The calculated elastic properties suggest a ductile behavior with metallic bonding for V2FeNiGe2 and a brittle behavior with covalent bonding for Hf2FeNiSb2. The thermodynamic properties (Debye temperature, melting temperature) are also predicted and discussed for the studied alloys. The alloys are found to be semiconducting with indirect band gaps of 0.53 eV for V2FeNiGe2 and 0.47 eV for Hf2FeNiSb2. We also computed and analyzed their optical properties (dielectric function, optical conductivity, refractive index, absorption index, and reflectance) and our calculations suggest that both materials have high absorption coefficient and optical conductivity in the UV as well as visible region. The results make them potential candidates for the manufacture of opto-electronic devices.

Insight on thermodynamic and thermoelectric properties of Ge based perovskites AGeO3 (A = Mg, Cd) for energy harvesting applications: A DFT approach

In this manuscript, transport properties like thermoelectric and thermodynamic properties of AGeO3 (A = Mg, Cd) perovskites have been performed in detail along with effect of chemical potential on various thermoelectric parameters. Furthermore, we present the electronic effects and thermodynamic stability of these materials. The MgGeO3 and CdGeO3 alloys have a gap of 3.368 and 2.555 eV, respectively, making them indirect band gap semiconductors. Furthermore, using a constant relaxation time approximation and semiclassical Boltzmann theory, the thermoelectric (TE) properties of both materials have been studied. The lattice thermal conductivity magnitudes for MGeO3 and CdGeO3 are 7.47 W/mK and 21.55 W/mK, respectively, at 300 K. Power Factor (PF) has been measured at approximately 0 chemical potential, or approximately 14 (1011 W/K2 ms) at 1200 K, 7.5 (1011 W/K2 ms) at 700 K, and 3.5 (1011 W/K2 ms) at 300 K for both MgGeO3 and CdGeO3. At room temperature, the electrical conductivities of MgGeO3 and CdGeO3 were measured to be 1.43 × 1015W/mK and 1.08 × 1015W/mK, respectively. Over a broad temperature range (0–1200 K), the thermodynamic parameters, such as heat capacity, entropy, thermal expansion, and Debye temperature, were also computed and discussed.

DFT based computational investigations of the physical properties of chalcogenide perovskites CsXS3 (X=P, Ta) for optoelectronic and photovoltaic applications

In this study, we employed density functional theory (DFT) calculations to systematically characterize the structural, mechanical, electronic, thermal, and optical properties of CsXS₃ (X = P, Ta), one of the most promising members of the chalcogenide perovskite (CP) family. Our theoretical findings align strongly with reported syntheses of other CP's, highlighting CsXS₃ (X = P, Ta) as most stable compounds. These materials satisfy the Born stability criteria, indicating robust mechanical stability, exhibit anisotropy, and demonstrate acceptable resistance to deformation under external stress. CsPS₃ and CsTaS₃ feature direct bandgaps of 1.91 eV and 0.51 eV, with small photocarrier effective masses, high absorption coefficients (1.6 × 10⁶ and 2.1 × 10⁶ cm⁻1), low reflectivity (15 % and 20 %), reduced loss function (0.6 and 0.4) and low refractive index (2.5 and 3.1), respectively. These properties underscore the potential of CsXS₃ (X = P, Ta)-based CP's for developing more efficient and stable optoelectronic devices and indoor photovoltaics. Notably, CsPS₃ is a strong contender for thermoelectric applications due to its lower Debye temperature compared to other CP's. Overall, our results demonstrate the great promise of CsXS₃ (X = P, Ta) chalcogenide perovskites in advancing the field of renewable energy and optoelectronics.

Band gap engineering of novel double perovskites Na2LiYX6 (X=Cl, Br) through halide ion replacement for solar cell and energy harvesting applications

Using the Perdew − Burke − Ernzerhof-generalized-gradient approximation (PBE-GGA) and PBE+SOC exchange − correlation functional, this work investigates the physical properties and energy storage capacity of novel double perovskite Halides Na2LiYX6 (X=Cl and Br) through Density Functional Theory (DFT) and semiclassical transport theory under ideal conditions. Thermal stability has been verified through the computation of thermodynamic parameters and formation energies. Brittle and anisotropic nature has been confirmed by the calculation of elastic and mechanical parameters. With PBE+SOC, the band gaps (Eg) for Na2LiYCl6 and Na2LiYBr6 are 2.90 and 3.76 eV, respectively, whereas with PBE-GGA, they are 3.061 and 3.824 eV, respectively. The analysis of the computed optical characteristics determines whether double perovskite halides are suitable for use in photovoltaic applications. The calculations for the transport properties were carried out using the BoltzTraP code. The effectiveness and transport mechanism for thermal energy conversion have been studied by determining the thermoelectric properties. To assess the stability at high temperatures and suitability for industrial applications, thermal properties such as heat capacity, entropy, Debye temperature, and thermal expansion are investigated. Overall, evaluations of the compounds’ thermoelectric characteristics show that they have a high-power factor and remarkably low thermal conductivity, which makes them ideal for energy harvesting devices.

Investigation on the hydrogen storage properties, electronic, elastic, and thermodynamic of Zintl Phase Hydrides XGaSiH (X = sr, ca, ba)

This study presents a comprehensive investigation of the electronic, mechanical, and thermodynamic properties of Zintl phase hydrides XGaSiH (X = Sr, Ca, Ba) using Density Functional Theory (DFT) and the FP-LAPW method within the WIEN2k package. Our analysis covers the structural stability, electronic properties, and hydrogen interaction mechanisms in these compounds. The hydrides exhibit narrow band gaps, with values ranging from 0.1 to 0.5 eV using GGA and LDA functionals, and 0.6–1.0 eV with mBJ-GGA and mBJ-LDA. The hydrogen storage capacities are determined to be 0.34 wt %, 0.47 wt %, and 0.40 wt % for SrGaSiH, CaGaSiH, and BaGaSiH, respectively, highlighting their potential for energy storage applications. Thermodynamic properties, evaluated through the quasi-harmonic Debye model, provide insights into the Grüneisen parameter, heat capacity, and thermal expansion coefficient over a range of pressures (0–50 GPa) and temperatures (up to 1000 K). Elastic constants reveal that these compounds are mechanically stable, with a notable anisotropy in the {100} plane and varying degrees of compressibility among the different hydrides. Our study further highlights the slightly ordered hexagonal Ga and Si layers, which contribute to the enhanced hydrogen storage capabilities of these materials. The compounds demonstrate high structural stability, facilitating effective hydrogen retention and release at practical temperatures, making them promising candidates for hydrogen storage applications. Additionally, the analysis of electronic band structures and density of states suggests significant conductivity potential, with band gaps ranging from 0.1 to 1.0 eV, depending on the computational method used. The unique combination of structural, electronic, thermodynamic, and mechanical properties in XGaSiH compounds positions them as valuable materials for renewable energy applications. These findings lay the groundwork for future research focused on optimizing these materials through structural modifications or doping to enhance performance metrics such as hydrogen storage capacity and electrical conductivity.

The role of grain boundary and alloy scattering within the Callaway model to calculate lattice thermal conductivity in GaN/AlN superlattice

The grain boundary and alloy scattering within the Debye-Callaway model were introduced to calculate the temperature-dependent lattice thermal conductivity (LTC) in the GaN/AlN superlattice. The superlattice layers are assumed to be grains, and the sample is then treated as a multigrain material. The computations include various physical parameters related to Aluminum alloy compositions, such as Debye temperature, atomic mass, lattice volume, density, alloy scattering factor and deformation energy. In general, the sample size effect on LTC in this superlattice structure was similar to any single component solids, but it has a significant influence from the grain boundaries represented by the thickness of layers in the form of LTCPeakpoint.=5.9925e0.0005L2 at the peak point maximum and LTC(600K)=0.344L at 600K, L is the sample size. The dislocations in these samples are controlled by the inbuilt AlN layers with the dependence of NDisl.=−0.542LAlN+7.4.

First-principle calculations to investigate mechanical and acoustical properties of predicted stable halide Perovskite ABX3

This work examines the predicted stable halide perovskites' elastic, acoustical, and thermal characteristics. The work uses the Full Potential-Linearized Augmented Plane Wave (FP-LAPW) technique through PBE-GGA to compute compounds in the WIEN2K algorithm. The ELATE program for the evaluation of elastic tensors to plot 2D and 3D graphs was also used. The bulk modulus, Young's modulus, shear modulus, anisotropy factors, Cauchy pressure, Pugh's ratio, Poisson's ratio, Kleinman's parameter, Lame's coefficient, Vicker's hardness, sound velocities, Gruneisen parameter and even melting and Debye temperature were computed. The mechanical and elastic properties are reported for the first time for most of the compounds, demonstrating that the investigated HPs—aside from TlBeF3, BaAgBr3, and CsTcl3—are mechanically stable and exhibit weaker resistance against shear distortion than they do to unidirectional compression. The results of Poisson's, Pugh's, and Frantsevich's ratios data prove that all materials are ductile except SrLiF3. The estimated Poisson's ratio data indicates the metallic bonding nature of HPs, whereas only SrLiF3 exhibits covalent behavior with ν = 0.23. Debye temperature for SrLiF3, ZnLiF3, ZnScF3, CsRhCl3, CsRuCl3, and CsBeCl3 is greater than 200 K which signifies their hardness, thermal conductivity, and high sound velocities. The large melting temperature values, make them suitable for high-temperature industrial applications. The anharmonicity effect is highest for CaCuBr3 (3.265) and lowest for SrLiF3 (1.402). The current approach calculates elastic and mechanical properties, providing a practical understanding of various physical processes and enabling technology developers to utilize compounds in diverse applications.

Crystal and thermodynamic properties of [formula omitted], (X = Al, Ga)

The crystal and thermodynamic properties of Tb2Ni2X (X = Al, Ga) are reported through measurements of X-ray diffraction (XRD), magnetic susceptibility, χ(T), magnetization, M(μ0H) and heat capacity, Cp(T). XRD pattern analysis confirms the orthorhombic W2CoB2-type structure with the space group of Immm. χ(T) at high temperature for both compounds follows the Curie – Weiss relationship giving an effective magnetic moment close to that expected for the trivalent Tb ion. The low-temperature χ(Cp) data indicate that both compounds order antiferromagnetically at TN = 41 K (40.4 K) and 41.5 K (41.4 K) for Al and Ga compounds, respectively. Cp(T) data of the nonmagnetic counterparts Y2Ni2X (X = Al, Ga) are well described by the Debye model giving a Debye temperature, θD = 236.9(4) K and 225.3(2) K for Al and Ga compounds, respectively. The low-temperature part of the 4f-magnetic contribution to the total heat capacity, C4f(T) can be described by the antiferromagnetic spin-wave dispersion, giving an energy gap Δsw = 47(3) K and 26(2) K for Al and Ga compounds, respectively. The 4f – magnetic entropy S4f(T) for both compounds reaches the value of 2Rln(2) close to their respective TN values.

Tuning of optical, thermodynamic, and thermoelectric properties of Cs2CuBiX6 (X = Cl, Br, I) halide perovskites for solar cells and energy harvesting applications

The double perovskites are outstanding materials for solar cells and transport applications to clean harvest energy. Therefore, the Cs2CuBiX6 (X = Cl, Br, I) are discussed comprehensively for energy harvesting by modified Becke and Johnson (mBJ) potential. The studied DPs fit the structural, mechanical, and dynamic stability scale by tolerance factor, Born–Huang criteria, and phonon dispersion band structures. The band gaps (1.20, 1.0, 0.70) eV for (Cl, Br, I) based DPs ensure the Cs2CuBiCl6 has an absorption band in the visible region while Cs2CuBiBr6 and Cs2CuBiI6 has an absorption band in the infrared region. Heavy elements’ spin–orbit coupling effect (Cs, Bi) reduces the band gap to 0.08 eV. Thermoelectric behavior regarding the merit scale against dopant carriers and temperature has been elaborated. The ultralow lattice thermal conductivity, large Debye temperature, hardness, and melting temperature increase their implication for thermoelectric and other thermodynamic applications. The variation in band gap makes them important for diverse optoelectric and thermoelectric applications. The Cs2CuBiCl6 with a band gap of 1.20 eV is suitable for solar cells, while Cs2CuBiBr6 and Cs2CuBiI6 with band gaps of 1.0 eV and 0.70 eV are significant for thermoelectric generators.

The effect of pressure on the physical properties of ScFe2 Laves phases

The physical properties of ScFe2 Laves phases with cubic (C15) and hexagonal (C14, C36) structures under ambient and high pressures are studied using the first-principles method and provide a comprehensive and in-depth analysis of the magnetic, elastic and dynamical properties. The spin magnetic moments of three structures decrease as pressure increases, and in the C36 structure, the spin reversal of Fe (6h) moment near 90 GPa is found. The critical pressures of magnetic collapse for the C14, C15 and C36 structures are 90, 160, and 170 GPa, respectively. The C15 structure is the most thermodynamically stable phase below 44.4 GPa, and a phase transition from C15 to C14 structure is observed. In the thermodynamic stability pressure range, with 0–44.4 GPa for C15 structure and 44.4–90 GPa for C14 structure, the C15 and C14 structures are both dynamically and mechanically stable. The C14 and C15 structures under high pressure are ductile structures with significant differences in elastic properties and anisotropy. Finally, the Debye temperature and sound velocity under high pressure are discussed in detail.