Large Bulk Modulus Research Articles

First-Principles Calculate the Stability, Mechanical Properties and Electronic Structure of Carbide MC, M2C and M6C in M50NiL Steel.

In this paper, the stability, mechanical properties and electronic structure of carbides in steel were calculated using the first-principles method based on the density functional theory (DFT). Firstly, the MC, M2C, M6C (M = Cr, Mo, V, Fe) carbides models were established. Then, different interphases' lattice constants, formation enthalpy, binding energy and elastic modulus were calculated. The stability, hardness, ductility and anisotropy of each phase were finally analyzed. The results show that these phases are stable, and the stability is closely related to the electron loss ability of its metal elements. The stronger the electron loss ability of its metal elements, the more stable the formed phase. As for MC carbides, MoC has the largest bulk modulus and hardness. As for M2C carbides, the Poisson's ratio of Cr2C is the smallest, and all phases except for Cr2C show toughness and ductility. The anisotropy of M6C carbides is relatively poor.

An approach for full space inverse materials design by combining universal machine learning potential, universal property model, and optimization algorithm

We present a full space inverse materials design (FSIMD) approach that fully automates the materials design for target physical properties without the need to provide the atomic composition, chemical stoichiometry, and crystal structure in advance. Here, we used density functional theory reference data to train a universal machine learning potential (UPot) and transfer learning to train a universal bulk modulus model (UBmod). Both UPot and UBmod were able to cover materials systems composed of any element among 42 elements. Interfaced with optimization algorithm and enhanced sampling, the FSIMD approach is applied to find the materials with the largest cohesive energy and the largest bulk modulus, respectively. NaCl-type ZrC was found to be the material with the largest cohesive energy. For bulk modulus, diamond was identified to have the largest value. The FSIMD approach is also applied to design materials with other multi-objective properties with accuracy limited principally by the amount, reliability, and diversity of the training data. The FSIMD approach provides a new way for inverse materials design with other functional properties for practical applications.

First-principles study on the structure, mechanical and thermodynamic properties of (Ti, Hf, Nb, Ta)C high-entropy carbide ceramics

High-entropy carbide ceramics (HECCs) have demonstrated extraordinary properties and broad application potential. However, the action mechanisms of metallic elements on the properties have not been understood in depth. In this study, the structural stability and the mechanical and thermodynamic properties of (Ti, Hf, Nb, Ta)C HECCs across a broad composition spectrum were systematically analyzed based on the density functional theory and Debye–Grüneisen model. The crystal structure was constructed and validated through experimental testing. The mechanical properties such as elastic moduli, ductility, hardness, and Poisson's and Pugh's ratios were calculated. Furthermore, the temperature dependence of bulk moduli, thermal expansion coefficients, and heat capacities of the HECCs were investigated. To interpret the elastic and toughening mechanisms of non-equiatomic HECCs, the electronic structures were investigated. The results indicate that the HECCs with a single solid solution phase of the FCC rock-salt structure are thermodynamically stable. The HECCs containing higher Nb and Ta contents have greater strength and stiffness, and those containing higher Ti and Hf contents exhibit greater hardness and brittleness than the equiatomic HECC. In addition, non-equiatomic HECCs containing higher Nb and Ta contents have larger bulk moduli and lower linear thermal expansion coefficients, which can be attributed to the stronger covalent interaction among metallic elements and carbon. This study is expected to have an impact on designing ideal HECCs for high-temperature applications under extreme environments.

Low-temperature and high-pressure phase transitions of ionic liquid 1-decyl-3-methylimidazolium bromide

The phase behavior of an ionic liquid (IL) was investigated at low temperature (LT) and high pressure (HP). The utilized IL was 1-decyl-3-methylimidazolium bromide ([C10mim][Br]), whose cation possesses a long alkyl side-chain. The LT- and HP-crystal polymorphs of [C10mim][Br] were observed conducting small- and wide-angle X-ray scattering (SWAXS) experiments. Upon cooling, a liquid crystal was formed, which subsequently transformed into crystalline species with the modulated layered structure possessing the double Bragg reflection. In addition to the layered structure, the hybrid layered structure coexisted upon heating. At HP, 00ℓ Bragg reflections representing the layered structure were not observed in SWAXS patterns. The HP-crystal phase of [C10mim][Br] was characterized by double Bragg reflection in the low scattering wavevector region. The non-layered HP-crystal caused the large bulk modulus.

First-principles calculations to investigate the structural stability, electronic and mechanical properties of CuGa2 and Cu9Ga4

This paper aims to evaluate the service reliability of intermetallic compounds (IMCs) in Cu-Ga joints. It accomplished this by calculating the thermodynamic and mechanical properties of CuGa2 and Cu9Ga4, which are common IMCs in Cu-Ga low temperature interface reaction, based on the first-principles calculation. According to the calculation results of enthalpy of formation and binding energy, both CuGa2 and Cu9Ga4 are thermodynamically stable, and Cu9Ga4 exhibits superior thermodynamic stability compared to CuGa2. The mechanical properties of Cu9Ga4 are better than CuGa2, with larger bulk modulus, shear modulus and Young's modulus. By comparing the elastic modulus with that of IMCs of Cu-Sn system, Cu9Ga4 shows larger elastic modulus than η′-Cu6Sn5 and smaller than Cu3Sn. In addition, Cu9Ga4 exhibits excellent toughness. By fitting the thermal expansion coefficients of Cu, CuGa2 and Cu9Ga4, the result shows that the thermal expansion coefficients of Cu and Cu9Ga4 are better matched. Additionally, the rapid volume expansion of CuGa2 weakens the interaction force between its atoms, resulting in a faster decay of its bulk modulus. The prediction of the mechanical properties of Cu-Ga compounds provides a deeper understanding of their properties and is important for the understanding of the feasibility of low-temperature brazing of Cu-Ga soldering systems.

First-principles calculations to investigate structural, electronic, and elastic properties of Fe3SnC ternary alloy

In this paper, the structural, electronic, and elastic properties of Fe3SnC were calculated based on local density approximation (LDA) and generalized gradient approximation (GGA) in density functional theory (DFT). Compared with GGA, LDA underestimates lattice constants and overestimates binding energy and elastic constants. The calculated lattice constants are 3.76 Å (LDA) and 3.83 Å (GGA), respectively, and the latter is closer to the experimental values. With U correction in GGA and LDA, the magnetic properties of the system are shown in the band structure. The GGA calculation results are more accurate, and the calculated magnetic moment of Fe3SnC is 5.74μB. The band structure indicates that Fe3SnC is a metallic compound. The elastic constants show that Fe3SnC has a large elastic constant and bulk modulus, in which the C11 calculated by GGA is as high as 463.81GPa, and the Young's modulus is as high as 350.72GPa. This indicates that Fe3SnC is a potential cermet due to a strong deformation resistance. At the same time, with the minimum thermal conductivity of 1.65 W/mK calculated by the Cahill model.

Determination of the high-pressure domain of stability of BeSiO3 and characterization of its crystal structure and properties.

Using density-functional theory calculations, we determined the pressure domain of stability of beryllium metasilicate, BeSiO3, an elusive compound for which no stable polymorph is known until now. We found that BeSiO3 is stable at pressures above 9 GPa, a condition that makes it accessible with a large-volume press. After considering the cubic, orthorhombic, and hexagonal perovskite structures and the Ilmenite structure, known from related compounds, we propose that the most stable structure among them is the orthorhombic perovskite structure described by space group Pnma. The unit-cell parameters of this structure are a = 4.966 Å, b = 7.160 Å, and c = 4.374 Å. We also determined the frequencies of Raman and infrared phonons, the elastic constants and modulus, and the electronic band structure for the orthorhombic perovskite structure. Finally, the pressure dependence of unit-cell parameters was calculated. Compression was found to be slightly anisotropic, with the axial compressibilities decreasing following the sequence κb > κc > κa. In addition, we found that BeSiO3 is quite incompressible with a bulk modulus of 242 GPa, which makes it one of the less compressible silicates. To understand, such a large bulk modulus, both the quantum theory of atoms in molecules and the electron localization function decomposition were utilized to analyze the bonding and to relate it to the mechanical properties.

First-principles study on the mechanical properties of Al1-xTMxP

Using first-principles calculations, the mechanical properties of orthorhombic phase Al1-xTMxP (x = 0.0625, 0.125, 0.25; TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) crystals were studied. By analyzing the mechanical stability, it was found that Al0.75Zn0.25P is mechanical unstable, and the rest all mechanical stable. The mechanical properties of Al1-xTMxP were studied, including Bulk modulus, shear modulus, Young?s modulus, Poisson?s ration, ductility, Vickers hardness, and elastic anisotropy. It was found that Al0.75Ni0.25P has the largest Bulk modulus, the largest Poisson?s ratio. Al0.75Ni0.25P has the smallest shear modulus, the smallest Young?s modulus and the smallest Vickers hardness. The Al0.75Ni0.25P has the best ductility. Al0.75Ni0.25P and Al0.75Cu0.25P show strong elastic anisotropy, and the Al0.75Cu0.25P has the largest elastic anisotropy. Through the study of the mechanical properties of Al1-xTMxP, it was found that doping Ni into AlP is an effective means to tune its mechanical properties.

Giant magneto-optical Kerr effect and thermoelectric properties in CeBiPt half-Heusler by DFT

The mechanical, electronic, magneto-optic and thermoelectric properties of CeBiPt compound have been calculated based on density functional theory (DFT) calculations. This compound has ground state point in the ferromagnetic phase with elastic stability by large bulk modulus of 88.565[Formula: see text]GPa. Poisson’s coefficient of 0.257 represents the ionic bonds between atoms, while the anisotropy coefficient indicates the elastic isotropic nature of this compound. Also, phonon dispersion emphasizes to the dynamic stability of this compound. By the mBJ approximation, this case exhibits ferromagnetic behavior with a magnetic moment of 0.98[Formula: see text][Formula: see text]. Based on the magnetic behavior of this crystal, the Kerr effect angles ([Formula: see text]) are 3.6∘ at 3[Formula: see text]eV and [Formula: see text] at 5.4[Formula: see text]eV, respectively, therefore, the rotation angle of the ellipse light polarization ([Formula: see text]) in the edge of ultraviolet region shows a large polarization of light in the visible region. The negative Seebeck coefficient of CeBiPt compound at low temperature refers to the hole transfer, also the magnitude of the power factor at higher temperatures indicates this compound is suitable for use in power generator applications.

First-principles calculations to investigate elastic properties, chemical bonds, electronic properties, magnetic properties, and phonon spectrum of CuNFe3 and CuNCo3

In this paper, the elastic properties, chemical bonds, electronic properties, magnetic properties, and phonon spectra of CuNFe3 and CuNCo3 synthesized in the experiment are calculated by first principles. The results show they are ferromagnetic metal compounds with covalent and ionic bonds. CuNFe3 and CuNCo3 have large bulk modulus B, Young's modulus Y, and shear modulus G, which are 191.01 GPa, 202.33 GPa, 159.65 GPa, 247.01 GPa, 58.67 GPa and 95.26 GPa, respectively, which indicates that they have compressive solid resistance. The total magnetic moment of CuNFe3 is 6.96 μB, and that of CuNCo3 is 4.17 μB, which suggests that they have broad application prospects in magnetic storage, computer core, magnetic recording materials and other fields.

Effect of intermetallics on properties of Al-6.1Zn-2.3Mg-1.7Cu-0.15Zr-0.3Nd alloy: First-principles calculation

By combining thermodynamic calculations with experimental results, the intermetallics present in the Al-6.1Zn-2.3Mg-1.7Cu-0.15Zr-0.3Nd alloy during both casting and homogenization processes had been identified. The above results indicated that the main intermetallics in the as-casted and homogenized alloy are α-Al, MgZn2, Al2CuMg, Al3Zr and Al8Cu4Nd. The formation enthalpy, cohesive energy, fermi level, elastic constant and electronic structure of each intermetallics were calculated by first-principles based on density functional theory ( DFT). According to the DFT results, the effect of equilibrium phase on the corrosion resistance and strength and toughness of the alloy was discussed. Among them, the fermi level difference between MgZn2 and α-Al is the largest, most likely to form a micro-corrosion battery, inducing decline in corrosion resistance of the alloy, while the fermi level difference between Al8Cu4Nd phase and α-Al matrix is the smallest which have the optimal corrosion resistance. The alloying ability (formation enthalpy), stability (cohesive energy), melting point, and hardness are Al3Zr, Al8Cu4Nd, Al2CuMg, and MgZn2 in order of magnitude, Al8Cu4Nd has the largest bulk modulus and the best compression resistance, Al3Zr has the highest strength, lowest Poisson 's ratio and highest shear resistance, while MgZn2 has the best plasticity.

Pressure-driven evolution of upper critical field and Fermi surface reconstruction in the strong-coupling superconductor Ti4Ir2O

We report pressure-driven evolution of the superconducting transition temperature (${T}_{\mathrm{c}}$) and upper critical field ${B}_{\mathrm{c}2}$ $(0)$ of strong-coupling superconductor ${\mathrm{Ti}}_{4}{\mathrm{Ir}}_{2}\mathrm{O}$ that possesses an unusually large ${B}_{\mathrm{c}2} (0)$ at ambient pressure (AP). Our results reveal an extremely low-pressure coefficients of ${T}_{\mathrm{c}}$, i.e., $d{T}_{c}/dP\ensuremath{\approx}\ensuremath{-}0.047$ K/GPa for $P<15$ GPa and \ensuremath{-}0.017 K/GPa for $15<P<50$ GPa, presumably associated with an inherent large bulk modulus of $\ensuremath{\sim}252$ GPa. Interestingly, we find that its ${B}_{\mathrm{c}2}$ $(0)$ undergoes a smooth crossover at 35.6 GPa from well beyond to less than the Pauli paramagnetic limit ${B}_{\mathrm{p}}^{\mathrm{BCS}}(0)=1.84\phantom{\rule{0.16em}{0ex}}{T}_{c}$; i.e., the ${B}_{\mathrm{c}2}(0)\ensuremath{\approx}18.2 \mathrm{T}=1.7\phantom{\rule{0.16em}{0ex}}{B}_{\mathrm{p}}^{\mathrm{BCS}} (0)$ at AP decreases to $\ensuremath{\sim}5.8 \mathrm{T}=0.88\phantom{\rule{0.16em}{0ex}}{B}_{\mathrm{p}}^{\mathrm{BCS}} (0)$ at 50 GPa. The density-functional calculations predict the possible occurrence of pressure-induced Fermi surface reconstruction for the energy bands near the $K$ point with strong spin-orbit coupling in 31--41 GPa. The present work sheds more light on this intriguing superconductor capable of resisting large external compression and strong magnetic fields.

Computation of Finite Temperature Mechanical Properties of Zeolitic Imidazolate Framework Glasses by Molecular Dynamics

Mechanical properties of amorphous phases of metal–organic frameworks (MOFs), such as MOF glasses, are difficult to determine experimentally. Moreover, computational characterization is limited by the level of theory chosen for the description of interatomic interactions and is often computationally expensive. In this work, we have extensively investigated the computation of finite temperature mechanical properties of ZIF-4 in the crystal and glass phases. We critically assessed computational methodologies including ab initio molecular dynamics, reactive force fields, and classical force fields, based on a variety of glass models. We find that ZIF-4 glasses have a larger bulk modulus than the crystal and confirm previous studies that the density is larger for the glass phases. Moreover, we confirm in the case of zeolitic imidazolate framework (ZIF) glasses the relationship between density and bulk modulus, showing that obtaining models of correct density is key to the prediction of physical properties for these systems.

First-principles study the mechanical, electronic, and thermodynamic properties of Mg-Al-Mn ternary compounds

In recent years, magnesium alloys have been used more and more widely due to their excellent lightweight and good plasticity. But correspondingly, the requirements for the elastic modulus (E) are more demanding. Therefore, to improve the deficiency, we are committed to find a way to increase the E. In this work, the mechanical, electronic, and thermodynamic properties of the Mg-Al-Mn ternary compounds were explored effectively based on first-principles calculations. It was found that the stabilities of these six structures were verified by the phonon spectrum, cohesive energy, and density of state, which showed that Mg3(MnAl9)2 possessed the best stability. Furthermore, Mg3(MnAl9)2 also had the largest bulk modulus, shear modulus, and E with values of 78.39, 50.94, and 125.6 GPa, respectively, due to the high bond strength of Al-Al bonds, and this was also verified by Mulliken's population analysis. Not only that, the largest hardness was reflected in Mg3(MnAl9)2 with a value of 9.04 and 9.11 GPa in Chen's and Tian's models. Similarly, the thermodynamic results showed that Mg3(MnAl9)2 had the highest Debye temperature as a value of 540.29 K and the highest limiting thermal conductivity with values of 1.216 W m−1K−1 in Clarke's model and 0.945 W m−1K−1 in Cahill's model.

Ground-State Structure of Quaternary Alloys (SiC)1−x (AlN)x and (SiC)1−x (GaN)x

Despite III-nitride and silicon carbide being the materials of choice for a wide range of applications, theoretical studies on their quaternary alloys are limited. Here, we report a systematic computational study on the electronic structural properties of (SiC)x (AlN)1-x and (SiC)x (AlN)1-x quaternary alloys, based on state-of-the-art first-principles evolutionary algorithms. Trigonal (SiCAlN, space group P3m1) and orthorhombic (SiCGaN, space group Pmn21) crystal phases were as predicted for x = 0.5. SiCAlN showed relatively weak thermodynamic instability, while that of SiCGaN was slightly elevated, rendering them both dynamically and mechanically stable at ambient pressure. Our calculations revealed that the Pm31 crystal has high elastic constants, (C11~458 GPa and C33~447 GPa), a large bulk modulus (B0~210 GPa), and large Young's modulus (E~364 GPa), and our results suggest that SiCAlN is potentially a hard material, with a Vickers hardness of 21 GPa. Accurate electronic structures of SiCAlN and SiCGaN were calculated using the Tran-Blaha modified Becke-Johnson semi-local exchange potential. Specifically, we found evidence that SiCGaN has a very wide direct bandgap of 3.80 eV, while that of SiCAlN was indirect at 4.6 eV. Finally, for the quaternary alloys, a relatively large optical bandgap bowing of ~3 eV was found for SiCGaN, and a strong optical bandgap bowing of 0.9 eV was found for SiCAlN.

Electronic properties of -Mn-type non-centrosymmetric superconductor Re5.5Ta under hydrostatic pressure

We have studied the effect of hydrostatic pressure on the superconducting and normal state properties of the non-centrosymmetric superconductor Re5.5Ta using magnetotransport, magnetization, and band structure studies. The superconducting transition temperature () reveals a modest decrease of ∼0.52 K as the external pressure is raised to 8 GPa. We found the Maki parameter, both at ambient and high pressures, suggesting the significant role of the Pauli pair breaking effect. Furthermore, the lower critical field was found to decrease with a rate of −1.74 mT GPa−1 as pressure increases to 1.05 GPa. Analysis of the thermally activated flux flow region of using the Arrhenius equation reveals the coexistence of single and collective vortex states. Further analysis of the critical current density indicates that the surface and volume pinning centers coexist and remain unaffected with varying pressure. Band structure calculations were performed using density functional theory and reveal a large bulk modulus, ∼ 289 GPa with ∼ 3.7, suggesting poor compressibility. In addition, we found that the density of states at the Fermi level barely reduces, even at pressures of up to 20 GPa. This is consistent with the experimental observation of robust superconductivity under compression.

Structural, electronic and mechanical properties of Mo2GeC under strain engineering

A new type of nitride and carbide with excellent properties of metals and ceramics, known as MAX phase materials, is a new guide for structural modification in various engineering applications and novel technologies. The Mo 2 GeC MAX phase is regarded as a promising material for applications such as new coatings, high pressure resistant materials, and fission and fusion program reactors. In this work, the structural, electronic, and mechanical properties of Mo 2 GeC under strain engineering are predicted by first-principles calculations. When Mo 2 GeC is tensioned or compressed by various strain conditions, effective mass decreases and increases in electrical conductivity are observed. Under uniform biaxial strain, the degeneracy at the top of the valence band is significantly increased. Mo 2 GeC possesses small Young’s modulus, shear modulus, and large bulk modulus, indicating that it can be desired for large strain engineering applications. However, the layered structure of Mo 2 GeC leads to low shear strength and hardness, which makes it less resistant to shear deformation. We also investigate the structural deformation and mechanical properties of Mo 2 GeC in different directions of uniaxial tensile strain up to the fracture limit. For tension along the a -direction, the strain ε value is 45% when Mo 2 GeC reaches the ideal tensile strength. The different bond strengths of Mo 2 GeC explain its anisotropy and show more significant differences under different strain conditions. Our results provide a strategy for tuning the various properties of Mo 2 GeC. Mo 2 GeC is subjected to uniaxial strain in different directions

Phase transition and properties of ternary MgGeN2 under pressure: a first principles investigation

In this work the structural, electronic, mechanical and optical properties of MgGeN2 under pressure are investigated through the density functional theory based first principles computations using the recently proposed Strongly Constrained and Appropriately Normed (SCAN) functional. It was found that the orthorhombic structure is energetically stable at ambient conditions and a phase transition from orthorhombic phase to a newly found tetragonal phase occurs at about 23 GPa under hydrostatic compression. In addition, in the investigated pressure range, MgGeN2 does not follow the rule that the materials will become more metallic under pressure due to that the strengthened covalent bond will enlarge the band gap and enable the system more insulating. Therefore, for both the orthorhombic phase and the high pressure tetragonal phase, the band gap shows a monotonic increment along increasing pressure. A reduction of the band gap was accompanied with the phase transition. In addition, the high pressure phase has a much larger bulk modulus and shear modulus than the orthorhombic phase, together with an enhanced optical absorption and conductivity. Finally, the potential applications of pressure induced structural change and band tuning are interpreted.

Understanding the difference in bulk modulus between Y-doped SrCeO3 and Y-doped SrZrO3 by ultrasonic transmission method and density functional theory

Proton-conducting oxides are promising for applications in solid oxide fuel cells and steam electrolysis at intermediate temperatures (400–600 °C). The hydration reaction requires oxide ion vacancies and the protonic conductive species originate from this reaction. Increasing the proton concentration leads to higher proton conductivity but also expands the lattice volume, known as chemical expansion, which may lead to the mechanical failure of the oxide. Thus, it is important to clarify the factors that decrease the chemical expansion. A previous study suggested that chemical expansion could be suppressed by a large bulk modulus. Although this was only a qualitative argument, our study quantitatively clarifies the effect of the bulk modulus experimentally and theoretically. To examine the difference between Ce and Zr, which are typical elements in proton-conducting oxides, 6.25 mol% Y-doped SrZrO3 and SrCeO3 were prepared, and their bulk moduli were quantitatively evaluated. Y-doped SrZrO3 had a larger bulk modulus than Y-doped SrCeO3. Our results support the previous finding that proton-conducting oxides with large bulk modulus suppress chemical expansion. In addition, our theoretical calculations of the force constants showed that the difference in bulk modulus was caused by the Zr-O bonds being more rigid than the Ce-O bonds. Our results should provide useful guidelines for suppressing chemical expansion in proton-conducting oxides.

Experimental demonstration of scalable active metamaterials with interacting cells of tunable bulk modulus

Active metamaterials can be designed to exhibit acoustic properties that are challenging to obtain using passive structures without relying on narrowband resonant behavior. Arrangements of unit cells that independently sense the local acoustic conditions and produce a coherent response, which is determined by the gain of electronics between the sensor and driver, act as a material with programmable properties. Such an active metamaterial has been previously demonstrated, but only for a single or a few non-interacting cells due to a limited understanding of how the programmed gains relate to the effective properties. Recently we developed a polarized source model to address this challenge, and based on that work we now demonstrate experimentally an active metamaterial composed of interacting cells with programmable bulk modulus. Each unit cell consists of a speaker and microphone mounted in the bottom plate of a 2D waveguide, with electronics of adjustable gain stored underneath. The field generated by a 2 × 3 arrangement of cells in response to an incident pulse was compared to the simulated scattered field of the equivalent continuous material. By tuning the gain, we accurately reproduced the behavior of a medium with negative, fractional, and large relative bulk modulus.