Elastic Anisotropy Research Articles

Theoretical studies of the physical properties of solar material CuAlS2

The theoretical approach was employed to comprehensively investigate the structural, dynamical, band structure, optical characteristics, and elastic anisotropy of CuAlS2. The determined lattice parameters (a and c), elastic properties exhibit with the available data. The band structure and density of state indicates that CuAlS2 exhibits semiconductor properties, characterized by a direct band gap measuring approximately 1.791 eV. The mechanical stability and optical properties of CuAlS2 was calculated and analyzed.

Model and mesh selection from a mCRE functional in the context of parameter identification with full-field measurements

Abstract In this paper, we propose a general deterministic framework to question the relevance, assess the quality, and ultimately choose the features (in terms of model class and discretization mesh) of the employed computational mechanics model when performing parameter identification. The goal is to exploit both modeling and data at best, with optimized model accuracy and computational cost governed by the richness of available experimental information. Using the modified Constitutive Relation Error concept based on reliability of information and the construction of optimal admissible fields, we define rigorous quantitative error indicators that point out individual sources of error contained in the identified computational model with regards to (noisy) observations. An associated adaptive strategy is then proposed to automatically select, among a hierarchical list with increasing complexity, some parameterized mathematical model and finite element mesh which are consistent with the content of experimental data. In addition, the approach is computationally enhanced by the complementary use of model reduction techniques and specific nonlinear solvers. We focus here on experimental information given by full-field kinematic measurements, e.g. obtained by means of digital image correlation techniques, even though the proposed strategy would also apply to sparser data. The performance of the approach is analyzed and validated on several numerical experiments dealing with anisotropic linear elasticity or nonlinear elastoplastic models, and using synthetic or real observations.

A first-principles investigation of the structural, mechanical, dynamic, electronic, magnetic, and optical properties of Ti2AC (A = Cd, S) MAX phase compounds

Abstract MAX phase compounds have a unique blend of ceramic and metallic properties and have been established as promising materials for device applications. In the present work, we have investigated the structural, dynamical, mechanical, electronic, magnetic, and optical properties of Ti2CdC and Ti2SC MAX phase compounds using a density functional theory approach through the Vienna Ab initio Simulation Package. The structural, dynamical, and mechanical properties of both MAX phase compounds are studied and found to be stable. Additionally, the mechanical properties reveal that both compounds have hardness and a crystalline anisotropic, bond-stretching, and brittle nature. From the analysis of elastic anisotropy calculations, it is found that Ti2CdC has metallic-like bonding, while Ti2SC has covalent-like bonding. The electronic and magnetic properties of the Ti2CdC and Ti2SC compounds are determined, and it is found that they have metallic and non-magnetic properties for the generalized gradient approximation (GGA): Perdew–Burke–Ernzerh (PBE) functional, whereas they have metallic and magnetic properties for the GGA: PBE + U functional(U is Hubbard parameter). We have explored the optical properties of the considered materials and found that they have compelling interactions with electromagnetic radiation, notable values of absorption energy, that less transparency occurred at the lower energy region, and that they have high thermal properties. Based on the major findings of the above considered materials, Ti2CdC and Ti2SC can be used in the fields of optoelectronic devices, sensors, advanced photonic devices, infrared imaging, solar thermal collectors, thermal insulation, nuclear devices, and energy dissipation devices.

Research on shale dynamic and static elastic modulus and anisotropy based on pressurization history

The dynamic and static elastic parameters of rocks exhibit differences. It is of great practical significance to carry out experiments on dynamic and static elastic parameters of rocks under reservoir conditions and determine the conversion relationship between dynamic and static elastic parameters. In this study, shale oil samples from the second member of Kongdong sag in Dagang Oilfield were analyzed by triaxial compression experiments at different bedding angles and longitudinal and shear wave velocity tests. Dynamic and static stiffness coefficient, elastic modulus and acoustic wave velocity change under different directions of pressure and pressure relief. The results indicate that the P-wave velocity, fast shear wave velocity, slow shear wave velocity, dynamic and static Young’s modulus exhibit an increase as the confining pressure rises, and the parameters are greater during the unloading process than during loading process. At identical confining pressures, the dynamic Young’s modulus measured by cores with parallel bedding plane is greater than that measured by cores with vertical bedding plane. The dynamic and static elastic mechanical parameters of different bedding angles can be transformed under varying pressures, and the dynamic elastic mechanical parameters measured under varying levels of confining pressure can be transformed into static elastic mechanical parameters under equivalent confining pressures, which offer fundamental parameters for examining rock mechanics properties and serving as a reference for developing fracturing construction plans for oil and gas reservoirs.

A density functional theory perspective on the structural, elastic, thermal, and electronic properties of copper nitride doped with transition metal (Fe, Co, and Ni)

Abstract The present study demonstrates structural, elastic, thermal and electronic properties of transition metal M (M: Fe, Co and Ni) doped copper nitride (Cu3N) using pseudopotential based density functional calculations as implemented in Quantum ESPRESSO simulation code. The exchange-correlation is approximated by PBE-GGA functional. The doped matrices represented as Cu3NM are verified to be stable structures, both thermodynamically and mechanically. Tailoring of elastic properties and their anisotropy due to M doping has been successfully demonstrated through comprehensive analysis of the computed elastic stiffness coefficients, elastic moduli, elastic anisotropy factors and spatial variation of the elastic moduli, which were not explored yet. An increase in bulk modulus due to M doping ensures enhanced mechanical stability under isotropic stress. Conversely, while doping of Co and Ni enhances the shear resistance of the host material, Fe doping slightly reduces it. Superior ductile nature of all the studied systems predicts their suitability for application in flexible electronics. It is evident that doping of M substantially reduces the elastic anisotropy of Cu3N. Using the calculated elastic moduli, velocity of acoustic waves and its anisotropy for Cu3N and Cu3NM are also predicted. The anisotropy in the acoustic velocity of the studied materials recommends their potential application in acoustic devices with directional selectivity. It is also noticed that, while average acoustic velocity is reduced due to Fe doping, it increases for Co and Ni doping. Furthermore, analysis of computed Debye temperature and minimum thermal conductivity forecasts their employability as thermal barrier coatings. Finally, the calculations reveal ferromagnetic nature of Cu3NFe and Cu3NCo with respective induced magnetic moments of 2.71 and 1.47 μB/cell, recommending their potential application in spintronics. It is also proved that, the M-d ― Cu-d coupling stabilizes the ferromagnetic ordering in such magnetic systems. On the other hand, Cu3NNi is observed to be non-magnetic.

Anisotropic Elasticity, Spin-Orbit Coupling, and Topological Properties of ZrTe2 and NiTe2: A Comparative Study for Spintronic and Nanoscale Applications.

The present work investigates the interfacial and atomic layer-dependent mechanical properties, SOC-entailing phonon band structure, and comprehensive electron-topological-elastic integration of ZrTe2 and NiTe2. The anisotropy of Young's modulus, Poisson's ratio, and shear modulus are analyzed using density functional theory with the TB-mBJ approximation. NiTe2 has higher mechanical property values and greater anisotropy than ZrTe2. Phonon dispersion analysis with SOC effects predicts the dynamic stability of both compounds. Thus, the current research unifies electronic band structure analysis, topological characterization, and elastic property calculation to reveal how these transition metal dichalcogenides are influenced by their structural, electronic, and mechanical properties. The results obtained in this work can be used in the further development of spintronic and nanoelectronic devices.

Effect of pressure-induced lattice distortion on physical properties of L10-FeNi ordered alloy

The ground-state properties of tetragonal L10 type FeNi alloy have been thoroughly studied, while its physical properties under high pressure are poorly understood. Here, the effect of pressure on the structural, magnetic, mechanical and dynamical properties of L10-FeNi are systematically investigated from the first principles calculations. The critical pressure of ferromagnetic collapse is detected to be 250 GPa, and the system is mechanically and dynamically stable below the critical pressure. The pressure-induced lattice distortion is identified in the pressure range of 80-150 GPa. Within this pressure range, the magnetic moments of the system decrease dramatically, the elastic constants C12, C13, C33 and bulk modulus B show softening behavior, and consequently the ductility, longitudinal sound velocity, and acoustic Grüneisen constant exhibit softening behavior, while the elastic anisotropy increase sharply. Furthermore, there are significant variations in magnetocrystalline anisotropy, coercivity, maximum magnetic energy product and magnetic hardness parameters within the pressure range of lattice distortion. More interesting is the discovery that the pressure-induced lattice distortion triggers a transition from semi-hard to hard magnet near 130 GPa.

Density functional theory study of Mg–Ho intermetallic phases

Abstract The present study explores the structural, phase stability, mechanical, and electrical properties of Mg–Ho intermetallic phases, namely Mg24Ho5, Mg2Ho, and MgHo. The investigation is conducted using the first-principles plane-wave pseudopotential method within the framework of density functional theory, as implemented in the Vienna Ab initio Simulation Package. The primary objective of this research is to illuminate the phase stability and mechanical behavior of these compounds, which are of paramount importance for their potential applications in magnesium alloys. The study determines the formation enthalpy (ΔH) and elastic constants (C ij ) for each intermetallic phase and calculates the elastic moduli of the corresponding polycrystalline materials. The findings of this study reveal that the MgHo phase exhibits the highest absolute value of formation enthalpy (ΔH = −8.01 kJ·mol−1), indicating its superior stability among the three investigated intermetallic phases. As the concentration of Ho in Mg increases, the G/B ratio for the phases decreases from 1.02 to 0.60 (>0.57), suggesting that the intermetallic phases are stable, albeit brittle. The elastic anisotropy index (A U), derived from the elastic constants (C ij ), follows an ascending order of Mg24Ho5, Mg2Ho, and MgHo, signifying that MgHo possesses the most favorable elastic anisotropy among the studied phases.

Pressure induced structural, anisotropy and thermal characteristics of MgIn2S4

The structural parameter, elastic anisotropy, and thermal properties of cubic MgIn2S4 under pressures is examined using first principles techniques. The determined lattice constant exhibits a high level of concurrence with the values reported in existing literature. Based on the mechanical characteristics, there is an observed enhancement in both ductility and anisotropy of MgIn2S4 under increased pressure. The investigation focuses on the thermal characteristics, encompassing the impact of temperature and pressure on key parameters such as Debye temperature, Grüneisen constant et al.

Acoustic Phonon Scattering in Free‐Standing Anisotropic Silicon Plates

The electron–acoustic‐phonon interaction in a free‐standing anisotropic Si plate with (001) surface is studied taking into account the elastic anisotropy of the Si crystal and the modulated phonon modes. The interaction potential is derived from the modulated phonon modes and the anisotropic deformation potential constants. The effective deformation potential constant Dac is then calculated considering only the lowest electronic sub‐band. In the quantum well model for the electronic states, it is shown that the effective deformation potential for the modulated phonons in an anisotropic Si plate becomes Dac ≈ 13 eV in the thinner region of the plate thickness . It is also shown that both the phonon modulation and the crystal anisotropy have non‐negligible effects on the effective deformation potential and electron mobility.

Molecular dynamics investigation of the elastic, mechanical, and anisotropic features of hexagonal (2H) diamond under extreme temperatures

2H diamond (lonsdaleite) is a promising material for contemporary science. However, there is still no well documented experimental or theoretical work for 2H diamond at high temperatures. Therefore, this work is the first theoretical contribution for the titled features of 2H diamond. The elastic constants decline with rising temperature and conform the Born stability. Both Pugh ratio and Poisson’s ratio results indicate the brittle character of 2H diamond. Both monotonic and non-monotonic hardness behavior with a notable elastic anisotropy were obtained and discussed. Presented results of this work for 2H diamond aligns well with available literature of other 2H materials.

Factors of stability of wells in reservoirs of underground gas storage facilities

Preserving the integrity of wells and preventing sand production processes are among the key problems in the operation of underground gas storage facilities. Previously, the authors have stated that a key role in the processes of destruction and sand production is played by changes in formation pressure in the reservoir as a whole, since it has a decisive influence on the magnitude of the stresses acting in the vicinity of the wells. This thesis differs from the point of view of many researchers who associate these negative processes with a change in the stress state in the bottomhole zone of the formation caused by drawdown/overbalance in wells. The main goal of the article is to study the influence of unequal components of the initial stress state, as well as elastic and strength anisotropy of reservoir rocks on the stability of wells. It is shown that the presence of unequal components of the initial stress state and elastic anisotropy can lead to stress concentrations on the well contour that differ significantly from the isotropic case. It is also shown that in the presence of strength anisotropy, a change in the location of the points of the beginning of well destruction can be observed. The calculations performed have been confirmed by experimental studies carried out on rocks of the Uvyazovsky underground gas storage facility under conditions of true triaxial independent loading.

Powder Metallurgy Processing to Enhance Superelasticity and Shape Memory in Polycrystalline Cu-Al-Ni Alloys: Reference Material for Additive Manufacturing.

Shape memory alloys (SMAs) are functional materials with a wide range of applications, from the aerospace sector to the biomedical field. Nowadays, there is a worldwide interest in developing SMAs through powder metallurgy like additive manufacturing (AM), which allows innovative building processes. However, producing SMAs using AM techniques is particularly challenging because of the microstructure required to obtain optimal functional properties. This aspect is critical in the case of Cu-Al-based SMAs, due to their high elastic anisotropy, making them brittle in polycrystalline form. In this work, we approached the processing of a Cu-Al-Ni SMA following a specific powder metallurgy route: gas atomization of a pre-alloyed melt; compaction of the atomized powders through hot isostatic pressing; and a final hot rolling plus thermal treatments. Then, the microstructure of the material was characterized by electron microscopy showing a specific [001] texture in the rolling direction that improved the functional behavior. The successive processing steps produce an increase of about 40 °C in the martensitic transformation temperatures, which can be well controlled and reproduced through the developed methodology. The thermomechanical functional properties of superelasticity and shape memory were evaluated on the final SMA. Outstanding, fully recoverable superelastic behavior of 4.5% in tension, as well as a ±5% full shape memory recovery in bending, were reported for many cycles. These experiments demonstrate the enhanced mechanical and functional properties obtained in polycrystalline Cu-Al-Ni SMAs by powder metallurgy. The present results pave the road for producing this kind of SMA with the new AM technologies, which always produce polycrystalline components and can improve their processes taking the powder metallurgy SMA, here produced, as reference material.

A first-principles investigation of XZn2Si2 (X = Ca, Sr, Ba) Zintl compounds: structural, elastic, electrical, optical and thermoelectric properties

Abstract These days, researchers are digging deep into the Zintl family of chemicals to uncover its many useful physical characteristics. Using a first-principles approach, this study investigates novel Zintl family XZn2Si2 (X = Ca, Sr, Ba) compounds for their different properties. The structural and electrical properties are represented by PBE-GGA and TB-mBJ potentials, respectively. The equilibrium structural parameters, which change with ionic radii, are obtained by optimization. The computations of the elastic constants confirmed the mechanical stability of the compounds. Elastic moduli, melting temperature, hardness, Debye temperature and acoustic properties are widely described. The compounds’ elastic anisotropy also discussed and extensively. The three compounds’ metallic origin was disclosed by their band structures. Chemicals exhibiting a high degree of valence band p-d hybridization. The compounds exhibit a combination of ionic and covalent bonding. In order to study the interaction between light and matter, the optical reflectivity, optical conductivity, and absorption coefficient are computed. In contrast to other compounds, CaZn2Si2 exhibits n-type transport. Among the compounds, CaZn2Si2 has the best figure of merit and may find use in thermoelectric devices.

Ab initio study of phase stability, elastic anisotropy, and minimum thermal conductivity of MnB2 in different crystal structures

Abstract The phase stability, elastic anisotropy, and minimum thermal conductivity of MnB2 in different crystal structures have been investigated by first-principles calculations based on density functional theory. The results found that P63/mmc (hP6-MnB2), P6/mmm (hP3-MnB2), Pmmn (oP6-MnB2), R 3 ¯ m (hR3-MnB2), Pnma (oP12-MnB2), and Immm (oI18-MnB2) all exhibit mechanical and dynamic stability under environmental conditions, and the sequence of phase stability was hP6 > hR3 > oP6 > oI18 > oP12 > hP3. In addition, Vickers hardness calculations indicated that hP6, hR3, oP6, and oI18 of MnB2 have potential as hard materials, while hP3 and oP12 are not suitable as hard materials. Moreover, the elastic anisotropy of different MnB2 phases were also comprehensively investigated. It is found that the anisotropic order of bulk modulus is oP12 > hP3 > hP6 > hR3 > oI18 > oP6, while that of Young’s modulus is oP12 > hR3 > hP6 > oP6 > hP3 > oI18. Furthermore, the minimum thermal conductivity of different MnB2 phases was evaluated by means of Clarke’s and Cahill’s models. The results suggested that these MnB2 diborides are all not suitable as thermal barrier coating materials.

Density functional theory investigation of the phase transition, elastic and thermal characteristics for AuMTe2(M = Ga, In) chalcopyrite compounds.

We explored the pressure-induced structural phase transitions and elastic properties of AuMTe2 (M = Ga, In) using the full-potential linearized augmented plane wave method within the framework of density functional theory, applying both generalized gradient and local density approximations. Thermodynamic properties were further assessed through the quasi-harmonic model. We determined the transition pressures for the phase shift from the chalcopyrite structure to the NaCl rock-salt phase in both AuGaTe2 and AuInTe2. Additionally, we calculated and analyzed mechanical properties, such as bulk modulus, shear modulus, Young's modulus, Poisson's ratio, elastic anisotropy, ductility versus brittleness, and hardness for the polycrystalline forms of AuMTe2 (M = Ga, In). The study also examined how temperature and pressure affect the Debye temperature, heat capacities, thermal expansion, entropy, bulk modulus, Grüneisen parameter, and hardness, utilizing the quasi-harmonic Debye model.

Rock Physics Modeling Studies on the Elastic and Anisotropic Properties of Organic-Rich Shale

Shale gas reservoirs have a large amount of resources, a wide range of burial, and great development potential. In order to evaluate the elastic properties of the shale, elastic wave velocity and anisotropy measurements of Longmaxi shale samples were carried out in the laboratory. Combined with the results of back scattering scanning electron microscopy (SEM) and digital mineral composition tests, the relationship between the anisotropy and the mineral components of the shale samples is discussed. It is found that the clay and kerogen combination distributed with an inorganic mineral background is the main cause of anisotropy. Then, the elastic properties of the organic-rich shale are analyzed with the anisotropic differential equivalent medium model (DEM). The clay and kerogen combination is established with kerogen as the background medium and clay mineral as the additive phase. The bond transformation is used to rotate the combination so that its directional arrangement is consistent with the real sedimentary situation of the stratum. Then, the clay and kerogen combination is added to the inorganic mineral matrix, with the organic and inorganic pores added to characterize the anisotropy of the shale to the greatest extent. It is found that the error between the wave velocity results calculated from the model and measured in the laboratory is less than 10%, which means the model is reliable. Finally, the effects of the microcracks and aspect ratio, kerogen content, and maturity on the elastic and anisotropic properties of shale rocks are simulated and analyzed with this model. The degree of anisotropy increases with the decrease in the pore aspect ratio and the increase in the microcracks content. The greater the kerogen content and maturity, the greater the anisotropy of rock. This study is of great significance for predicting the “sweet spot” of shale gas and optimizing hydraulic fracturing layers.

Ab initio calculations of second-, third-, and fourth-order partial and inner elastic constants of diamond

By means of ab initio calculations, a unified framework is presented to investigate the effect of internal displacement on the linear and nonlinear elasticity of single diamond crystals. The calculated linear and nonlinear elastic constants, internal strain tensor and internal displacement in single diamond crystals are compatible with the available experimental data and other theoretical calculations. The complete set of second-, third- and fourth-order elastic constants and internal strain tensor not only offer a better insight into the nonlinear and anisotropic elasticity behaviors, but also shows us the basic internal mechanical response of diamond. This study provides a route to calculate the nonlinear internal and external elasticity response in a nonprimitive lattice.

First-principles calculations on the mechanical, electronic and thermodynamic properties of t-C88 carbon allotrope under high pressure

The new tetragonal carbon allotrope t-C88, which is the subject of this work, is distinguished by its distinct mechanical performance at high pressure and structural characteristics. t-C88 shows hybridization of sp2 and sp3 carbon atoms, in contrast to other carbon compounds that are mostly made of sp2-hybridized carbon atoms. We investigated the elastic characteristics and anisotropy of t-C88 at different pressures (0–20 GPa) using first-principles computations. Our results show that t-C88 exhibits strong elastic anisotropy, especially above 15 GPa, and retains mechanical stability by meeting Born-Huang requirements. In order to emphasize the material's reaction to high pressure, this study offers a wealth of information on the following criteria: Poisson's ratio (v), bulk modulus (B), shear modulus (G), Young's modulus (E), elastic constants (Cij), and universal anisotropy (AU). Interestingly, t-C88 shows more resistance to compressional deformation than shear deformation. The high B/G ratio of t-C88 indicates that its mechanical characteristics indicate that it will become ductile with increasing pressure. Moreover, the understanding of t-C88 under high-pressure conditions will open viable options for various applications, including high-performance composites for enhanced strength and durability, protective coatings requiring superior mechanical stability, advanced sensors due to its tuneable electronic properties, energy storage devices leveraging its unique characteristics, and electronic components.

The effect of PBEsol GGA and mBJ potentials on the structural, electronic, optical, elastic and thermoelectric properties of A2BAuI6 (A = K or Rb or Cs, B = Sc or Y)

Perovskites systems are leading the photovoltaic technology now a days. For the consistent renewable energy applications new materials required with the desirable properties. In this work six new materials are being predicted which may be very useful for the renewable energy applications. The full potential scheme of linearized augmented plane wave with the local orbitals is used for the calculations with the PBEsol GGA and mBJ potentials for the exchange-correlation effects. The structural and elastic parameters of A2BAuI6 (A = K or Rb or Cs, B = Sc or Y) are computed, and the responses exhibits that such compounds are stable, have a ductile nature, and are described by a high elastic anisotropy. The bandgaps were identified via the electrical band structure computations for A2BAuI6 (A = K, Rb, Cs; B = Sc or Y) compounds as 1.25 eV, 1.64 eV, 1.24 eV, 1.62 eV, 1.25 eV and 2.04 eV with TB-mBJ + SOC approach. The calculated compounds have much dispersion in their bands and minimal carrier effective mass. Lattice thermal conductivity (KL) is computed via Slack's equation for all computed compounds are 0.29 × 1014 W/mK, 0.31 × 1014 W/mK, 0.29 × 1014 W/mK, 0.31 × 1014 W/mK, 0.39 × 1014 W/mK and 0.29 × 1014 W/mK, indicating a promising future for thermoelectric uses. The calculation of thermoelectric parameters, including the power factor, Seebeck coefficient, and figure of merit, serves another prospective purpose and confirms the potential high use of these materials in thermoelectric devices. Likewise, acceptable quality characteristics like long diffusion length, tunable band-gap, high mobility, am-bipolar charge transport, and high absorption reinforce these compounds which make them even more suitable for photovoltaic applications.