Nb Atoms Research Articles

First principles study of magnetic transition of strain induced monolayer NbSi<sub>2</sub>N<sub>4</sub>

The effective control of two-dimensional material magnetism is a frontier research field. In this work, the influences of in-plane biaxial tension strain on the electronic structure, magnetic properties, and Curie temperature of monolayer NbSi<sub>2</sub>N<sub>4</sub> are investigated by first-principles calculations based on density functional theory and Monte Carlo simulations in the frame of the Heisenberg model. We demonstrate that the monolayer NbSi<sub>2</sub>N<sub>4</sub> has favorable dynamic and thermal stability through the phonon spectral calculations and ab initio molecular dynamics simulations. It is found that the intrinsic monolayer NbSi<sub>2</sub>N<sub>4</sub> is a non-magnetic metal, which can be transformed into a ferromagnetic metal by 1.5% tensile strain. The electronic structure analysis of monolayer NbSi<sub>2</sub>N<sub>4</sub> shows that the ferromagnetism induced by tensile strain is caused by traveling electrons. There is a half-full band at the monolayer NbSi<sub>2</sub>N<sub>4</sub> Fermi level, which is mainly contributed by the dz<sup>2</sup> orbital of the Nb atom. When there is no additional strain, the band is spin-degenerate. Tensile strain can make this band more localized, which leads to Stoner instability, resulting in the ferromagnetic ordering of monolayer NbSi<sub>2</sub>N<sub>4</sub> traveling electrons. The stability of the ferromagnetic coupling is enhanced with the increase of the strain degree. The calculation results of the magnetic anisotropy energy show that the strain can make the direction of the easy magnetization axis of the monolayer NbSi<sub>2</sub>N<sub>4</sub> reverse from the vertical direction to the in-plane, and then back to the vertical direction. Furthermore, the strain can significantly increase the Curie temperature of monolayer NbSi<sub>2</sub>N<sub>4</sub>. The Curie temperature of monolayer NbSi<sub>2</sub>N<sub>4</sub> is 18 K at 2% strain and 87.5 K at 6% strain, which is 386% higher than that at 2% strain. Strain engineering can effectively control the magnetic ground state and Curie temperature of single-layer NbSi<sub>2</sub>N<sub>4</sub>. The research results are expected to promote the development of <i>MA</i><sub>2</sub><i>Z</i><sub>4</sub> materials in the field of mechanical sensing device design and low-temperature magnetic refrigeration.

Effect of single atomic layer graphene film on the thermal stability and hydrogen permeation of Pd-coated Nb composite membrane

Pd coated Nb-base composite membranes are preferable in the fields of hydrogen permeation. However, the rapid reduction of hydrogen permeability caused by high-temperature interfacial diffusion of Pd and Nb atoms hinders their large-scale application. In this paper, a single atomic layer graphene film was used for improving the thermal stability of a hydrogen-permeable composite membrane comprising a Pd coating on the Nb substrate. First, the graphene film was transferred onto the surface of the “clean” niobium substrate. Then a thin palladium coating was deposited on it by magnetron sputtering to form the niobium/graphene/palladium (Nb/Gr/Pd) composite membrane. The interfacial stability was evaluated in the temperature range of 673–973 K under vacuum, and the hydrogen permeation behavior was studied by gas-driven permeation method at 573–823 K. The results show that the single atomic layer graphene film can effectively compress the interdiffusion of Pd coating and Nb substrate and achieve a good hydrogen permeability below 823 K. However, it would be broken due to the micro-deformation of Nb substrate, the high mobility of Pd atoms, and the grain growth at a higher temperature. Therefore, it is concluded that the single atomic layer graphene film is unsuitable as an intermediate hindering layer for Nb-based hydrogen-permeable membranes.

First principle investigation of Niobium (Nb) doped MgO

This paper presents the structural, electronic, and magnetic properties of pure and Nb doped MgO, in its zinc blende and rock salt phase for small concentration. In our work, the full potential linearized augmented plane wave plus local orbital (FP-LAPW + lo) method, implemented in the WIEN2K simulation package and the Local Density Approximation (LDA) were employed. The results obtained show that pure MgO has a gap of 4.97 eV and Mg0.875Nb0.125O has a metallic character. The modifications in the band gap and magnetic properties of magnesium oxide mainly originate from the 4 d-orbitals of the Nb atoms. In comparison with Mg and O atoms (0.007 and 0.054), the magnetic data shows that the Niobium magnetic moment (1.3528 µβ) is the dominant one. As a result, the total magnetic moment of our component is equals to 2.9091 µβ. We consider that MgO and Mg0.875Nb0.125O could be promising candidates for electronic systems and related fields.

Tuning the magnetic anisotropy of transition-metal atoms on two-dimensional In2Se3 substrate via ferroelectric polarization switching

Exploring large and tunable magnetic anisotropy (MA) in a single magnetic atom is of merit for information storage due to the highest information data density. In this work, we studied the MA of transition-metal atoms X (X = Co, Fe, Ir, Mo, Nb, Ta, Ti, V, W) adsorbed on the surface of two-dimensional (2D) ferroelectric (FE) In2Se3 by first-principles calculations. We find that when the ferroelectric polarization of the In2Se3 is switched, the strengths of the MA for Co, Ir, Nb and Ti single atoms can be changed, while the directions of the MA for Fe, Mo, Ta, V and W single atoms are reversed. Calculated electronic structure and orbital-resolved magnetic anisotropy energy suggest that the variations in the occupation of spin-minority state and the exchange splitting of d orbitals at Fermi level by switching FE polarization are responsible for the change of the strength and direction of the MA on X atoms.

The formation mechanism of complex carbides in Nb-V microalloyed steel

The formation mechanism of complex precipitates in Nb-V microalloyed steel has been systematically studied by high resolution transmission electron microscopy (HRTEM) and atom probe tomography (APT). The results reveal that there are two precipitation mechanism: replacement and heterogeneous mode. The core–shell precipitate has been observed with double direction Moiré fringe, which is formed by the heterogeneous mechanism, while for the precipitates with uniform distributed V and Nb atoms, is formed by the replacement mechanism. These two modes both reduce the lattice misfit and promote precipitation. In addition, the APT result reveals that the ratio of V to Nb increases with the increase of particle size, which matches well with the previous TEM results.

Relativistic first-principles theory of Yu-Shiba-Rusinov states applied to Mn adatoms and Mn dimers on Nb(110)

We present a fully relativistic first principles based theoretical approach for the calculation of the spectral properties of magnetic impurities on the surface of a superconducting substrate, providing a material specific framework for the investigation of the Yu--Shiba--Rusinov (YSR) states. By using a suitable orbital decomposition of the local densities of states we discuss in great details the formation of the YSR states for an Mn adatom and for two kinds of Mn dimers placed on the Nb(110) surface and compare our results to recent experimental findings. In case of the adatom we find that the spin-orbit coupling slightly shifts some of the YSR peaks and also the local spin-polarization on the Nb atoms have marginal effects to the their positions. Moreover, by scaling the exchange field on the Mn site we could explain the lack of the $d_{x^2-y^2}$-like YSR state in the spectrum. While our results for a close packed ferromagnetic dimer are in satisfactory agreement with the experimentally observed splitting of the YSR states, in case of an antiferromagnetic dimer we find that the spin-orbit coupling is not sufficiently large to explain the splitting of the YSR states seen in the experiment. Changing the relative orientation of the magnetic moments in this dimer induces splitting of the YSR states and also shifts their energy, leading even to the formation of a zero bias peak in case of the deepest YSR state.

Effects of Mo equivalent on the phase constituent, microstructure and compressive mechanical properties of Ti–Nb–Mo–Ta alloys prepared by powder metallurgy

The Ti-(0–30)Nb-(2–11)Mo-3.5Ta (wt.%) alloys with the composition interval of 5.0 wt.% for Nb and 3.0 wt.% for Mo were prepared by hot isostatic pressing. The Ti–Nb–Mo–Ta alloys with high compressive strength and favorable ductility were obtained, which enabled the alloys to be used as novel structural or biomedical materials. The phase constituent, microstructure, and compressive properties were investigated. Although the compressive yield strength and the strain at failure showed different correlations to the Nb and Mo content, respectively, the two mechanical property parameters both showed distinctly monotonic correlations to the Mo equivalent. With the increasing Mo equivalent, the content of the α phase decreased, while that of the β phase increased. Simultaneously, the yield strength of the Ti–Nb–Mo–Ta alloys decreased, while the strain at failure increased. Quantitative analyses were then implemented on the grain refinement strengthening, the second-phase strengthening of the α phase, and the solid solution strengthening of the Nb and Mo atoms. After comparing the separate contributions of the above determining factors, it was confirmed that the second-phase strengthening was the dominating mechanism for improving the mechanical properties of the powder metallurgic Ti–Nb–Mo–Ta alloys.

Interactions of hydrogen with zirconium alloying elements and oxygen vacancies in monoclinic zirconia

Using Density Functional Theory with hybrid functionals, we calculate the interactions of hydrogen atoms with some point defects in monoclinic zirconia. We consider Nb and Sn substitution for Zr atoms as well as oxygen vacancies, the latter being the main defects present in the zirconia layer. They are formed during the corrosion of zirconium claddings in pressurized water reactors. We consider various charges for the complexes formed by hydrogen atoms and the aforementioned defects. The formation and binding energies are thus expressed as functions of the Fermi level in zirconia. We find that there is almost no interaction between H and Sn atoms, while a small but noticeable binding exists between H and Nb atoms. Conversely, hydrogen atoms bind strongly to oxygen vacancies which can accommodate up to 2 hydrogen atoms. We observe that there is a range of Fermi levels where the actual stable form of hydrogen is the H2 molecule and not isolated hydrogen ions. We integrate the calculated energies in a thermodynamical model to calculate the concentrations of the various forms of hydrogen. We observe that the driving parameters are the oxygen vacancy to hydrogen ratio and the temperature. There is a change in the main stable hydrogen species upon decrease of the vacancy concentration from hydrogen trapped in vacancies to interstitial forms of hydrogen. These results provide a possible rationale for the variation of hydrogen diffusion coefficient through the oxide layer observed experimentally in literature.

(Ti0.2V0.2Cr0.2Nb0.2Ta0.2)2AlC–(Ti0.2V0.2Cr0.2Nb0.2Ta0.2)C high‐entropy ceramics with low thermal conductivity

AbstractIn recent years, the microstructure and physicochemical properties of high‐entropy ceramics have received much interest by the combination of multiple principal elements. Herein, (Ti0.2V0.2Cr0.2Nb0.2Ta0.2)2AlC–(Ti0.2V0.2Cr0.2Nb0.2Ta0.2)C high‐entropy ceramics (M2AlC‐MC HECs) were prepared by the spark plasma sintering (SPS) technique, attributing to the structural and chemical diversity of MAX phases. The microstructure of M2AlC‐MC HECs was characterized from micron to atomic scales, and the phase composition of M2AlC‐MC HECs was analyzed by a combination of Maud and Rietveld analysis. The results indicate the successful solid solution of Ti, V, Cr, Nb, and Ta atoms in the M‐site of the 211‐MAX configuration, and all the samples show a classic layered structure. The weight percentage of (Ti0.2V0.2Cr0.2Nb0.2Ta0.2)2AlC in the M2AlC‐MC HECs was more than 90%. Furthermore, the thermoelectric properties of M2AlC‐MC HECs were investigated for the first time in this study, and the electrical conductivity and thermal conductivity of HECs are 3278 S cm−1 and 2.78 W m−1 K−1at 298 K, respectively.

Interface structure of (130) twin in the U-14.0 at.% Nb alloy: an experimental and theoretical study

In this work, we report an experimental and theoretical study of the (130) twin system in the U-14.0 at.% Nb alloy using aberration-corrected TEM in combination with first-principles calculations. We clearly give the atomic structure of (130) twin and its twin boundary energy for the first time. We evidence that the widely used (130) twin system in pseudo-orthorhombic system is in fact the (101) twin system in the monoclinic crystal system. Through first-principles calculations, we also find that the local atomic structure of Nb significantly affects the twin boundary energy due to the depleted charge zone at Nb atom and charge-rich zone around Nb atom. These results may help us better understand the deformation mechanism in low-symmetry U metal and U-Nb alloys.

Unidirectional Kondo scattering in layered NbS2

Crystalline defects can modify quantum interactions in solids, causing unintuitive, even favourable, properties such as quantum Hall effect or superconducting vortex pinning. Here we present another example of this notion—an unexpected unidirectional Kondo scattering in single crystals of 2H-NbS2. This manifests as a pronounced low-temperature enhancement in the out-of-plane resistivity and thermopower below 40 K, hidden for the in-plane charge transport. The anomaly can be suppressed by the c-axis-oriented magnetic field, but is unaffected by field applied along the planes. The magnetic moments originate from layers of 1T-NbS2, which inevitably form during the growth, undergoing a charge-density-wave reconstruction with each superlattice cell (David-star-shaped cluster of Nb atoms) hosting a localised spin. Our results demonstrate the unique and highly anisotropic response of a spontaneously formed Kondo-lattice heterostructure, intercalated in a layered conductor.

Atomic structure of liquid refractory Nb5Si3 intermetallic compound alloy based upon deep neural network potential

The knowledge of atomic structure for liquids, especially for liquid alloys with complex crystal structure and high liquidus temperatures, remains poorly understood. In this work, we have extended the development of deep neural network (DNN) potential for liquid Nb5Si3. The DNN potential captures the structural features of liquid alloys compared with ab initio results. The chemical short-range order parameter suggests that there exists strong affinity between Nb and Si atoms. The dynamic property was investigated, and the diffusion coefficient obeys the Arrhenius relationship. The atomic structure has been subsequently explored for normal and undercooled liquid Nb5Si3. Large amounts of fivefold symmetry Honeycutt–Andersen pairs have been identified in liquid Nb5Si3. However, due to the violent thermal motion in a high-temperature Nb5Si3 melt, icosahedral symmetry and distorted icosahedrons (ICOs) account for little proportion according to Voronoi polyhedron (VP) analysis. The effect of thermal motion on VPs has been discussed. Except from the well documented ⟨0,2,8,2⟩ and ⟨0,1,10,2⟩ distorted ICOs, six more quasi-ICOs (⟨0,1,9,3⟩, ⟨0,2,8,1⟩, ⟨0,2,8,4⟩, ⟨0,2,8,5⟩, ⟨0,1,10,3⟩, and ⟨0,1,10,4⟩) have been proven to deform from ICOs at high temperatures. The local environment motif obtained by the atomic cluster alignment method demonstrates the existence of dominant distorted ICOs. At last, the atomic structure during melting process is discussed by VP analysis. It is found that ⟨0,2,8,1⟩, ⟨0,2,8,2⟩, ⟨0,2,8,5⟩, and ⟨0,1,10,4⟩ prefer to form at the beginning of the melting but rapidly reduce when it is fully melted.

MD simulation of interactions of atomic displacement cascades with β-Nb precipitates in a zirconium matrix

In this work, we investigated the effect of spherical binary precipitates and needle-shaped nanoparticles of β-Nb on the evolution of cascade processes in the Zr matrix using the method of molecular dynamics and many-body interatomic potentials. For a case of spherical precipitates, the formation of the interphase region with length of ~ 10 Å was observed. The fraction of the Zr atoms in the precipitate increased during the cascade processes. The Nb atoms, which were initially inside the precipitate, did not leave the boundaries of the interphase region after relaxation of the model crystallite. After the cascade process, the Nb atoms were detected Zr matrix at a distance of no more than 5 Å from interphase boundary. Point defects, as well as their clusters, are formed mainly near the surface of the precipitate. In a case of needle-shaped nanoparticles, a slight “blurring” of the particle boundaries with an increase in the number of niobium atoms in the near- boundary region were observed. After the atomic displacement cascade, part of the niobium atoms moved from nanoparticle into the near-boundary region. Only a few niobium atoms moved into the α-phase matrix outside the near-boundary region. No cases of significant dissolution of the nanoparticle were observed. We also observed the formation of clusters consisting of a mixture of vacancies and SIAs in the structure of the nanoparticle.

Charge controlled capture/release of CH4 on Nb2CTx MXene: A first-principles calculation

Methane is not only the main cause of coal mine accidents but also a contributor to global warming, meanwhile, it is clean energy. It is necessary to find an advanced material which can capture methane efficiently for its utilization. In this paper, the adsorption of CH4 gas molecules on Nb2CTx(T = O, F, Cl, OH) is studied by first-principles calculation. The results indicate that the adsorption of CH4 on Nb2CTx(T = O, F, Cl, OH) is weak, and the adsorption of CH4 on Nb2C(OH)2 is the best. The calculation results of binding energy and cohesive energy show that Nb2CO2 has the best stability. The adsorption behavior of CH4 on Nb2CO2 under charge control is further studied. With the increase of negative charge state in the system, the adsorption of CH4 on Nb2CO2 is significantly enhanced, from physical adsorption to chemical adsorption; when the charge state of the system is greater than or equal to −2, Nb2CO2 can capture CH4 effectively, and the charges transferred from Nb2CO2 to CH4 mainly come from Nb atom. After the removal of the extra charge, the adsorption of CH4 on Nb2CO2 becomes weak and returns to physical adsorption state; CH4 gas molecules are easy to desorb. Therefore, Nb2CO2 can capture and release CH4 molecules by regulating the charge state of Nb2CO2, and Nb2CO2 is expected to become an excellent candidate material for CH4 capture/release.

Mechanical and microstructural properties of a CoCrFe0.75NiMo0.3Nb0.125 high-entropy alloy additively manufactured via cold-spray

We present a combined experimental and computational investigation of the mechanical properties of a CoCrFe0.75NiMo0.3Nb0.125 (composition in molar ratio) high-entropy alloy additively manufactured via cold spray. We find that the sprayed alloy exhibits extraordinary mechanical properties under compression, reaching yield stress of ~1745 MPa, ultimate stress of ~2622 MPa, and a maximum strain at failure of ~9%. These exceptional mechanical properties are the result of four independent hardening mechanisms. First, using ab initio simulations, we find that non-equiatomic compositions increase the enthalpy of mixing, promoting better solubility of solute Mo and Nb atoms while simultaneously preserving the electronegativity of the base alloy. The higher solubility results in solid-solution hardening and nanosized precipitate formation, promoting additional hardening. These effects are confirmed in the experimental characterization of the manufactured HEA, where nanosized precipitates of ~226 ± 65 nm in size are identified. Additional hardening effects are associated with the manufacturing process, where the high-velocity impacts of the microparticles promote dynamic recrystallization through dislocation emission and grain refinement. To understand the dynamic recrystallization of particles, high-velocity impact simulations using molecular dynamics are performed. We find that when particles reach a critical impact velocity ( ~600–800 m ⋅ s−1), the dislocation density reaches a maximum, and grain refinement is maximized. The decaying wave pressures developed during the impact generate gradual refinement levels, leading to heterogeneous microstructures combining nano and micro grains, which was later confirmed experimentally using electron backscatter diffraction. These subtle atomic and microstructural features result in outstanding experimentally evaluated yield and ultimate stresses compared to other high-entropy alloys with similar compositions.

The Electronic, Structural, and Optical Properties of CaNb2O6 Compound: Theoretical Study

Based on the density functional theory (DFT) as incorporated in the Wien2k package, the lattice parameters and atomic position of calcium niobate (CaNb2O6) were optimized. Furthermore, the electronic, optical, and structural properties of the relaxed compound were calculated. Relaxed calcium niobate presents a direct band gap with 3.5 eV, which makes it a good candidate for photovoltaic applications. The DFT calculation reveals that the O atoms make the major contributions in the valence band, while Nb and Ca atoms are the dominant contributors in lower and upper portions of the conduction band, respectively. Moreover, the optical properties of compounds such as refractivity, dielectric constant, reflectivity, etc. are calculated and discussed in detail.

Vibrational Analysis of Paraelectric–Ferroelectric Transition of LiNbO3: An Ab-Initio Quantum Mechanical Treatment

The phase transitions between paraelectric (PE) and ferroelectric (FE) isomorph phases of LiNbO3 have been investigated quantum mechanically by using a Gaussian-type basis set, the B3LYP hybrid functional and the CRYSTAL17 code. The structural, electronic and vibrational properties of the two phases are analyzed. The vibrational frequencies evaluated at the Γ point indicate that the paraelectric phase is unstable, with a complex saddle point with four negative eigenvalues. The energy scan of the A2u mode at −215 cm−1 (i215) shows a dumbbell potential with two symmetric minima. The isotopic substitution, performed on the Li and Nb atoms, allows interpretation of the nontrivial mechanism of the phase transition. The ferroelectric phase is more stable than the paraelectric one by 0.32 eV.

Effects of doping Ti, Nb, Ni on the photoelectric properties of monolayer 2H–WSe2

The photocurrent of Ti, Nb, Ni substitution-doped monolayer 2H–WSe 2 is calculated by the first-principles method based on the Keldysh nonequilibrium Green's function-density functional theory. The photogalvanic effect(PGE) photocurrent can be generated in the monolayer 2H–WSe 2 under the vertical irradiation of linear polarized light, However, it is generally very small. Calculation results show that the Nb and Ti-doped systems exhibit the characteristics of semi-metal, while the Ni-doped system tends to transform into metals. The substitutional doping of Nb, Ti, and Ni atoms can effectively enhance the photocurrent and the polarization sensitivity of monolayer 2H–WSe 2 .This excellent performance is mainly attributed to the fact that the doping introduces multiple impurity energy bands crossing the Fermi energy level, which becomes a bridge for electronic transitions, thus effectively enhancing the photocurrent. • Background and Significance: The research on the modification of monolayer 2H-WSe 2 by doping has become increasingly popular, and its doping system has shown great application potential. But the theoretical calculation of doped 2H-WSe 2 is relatively less in terms of the photogalvanic effect. Therefore, the photocurrent of Ti, Nb, and Ni-doped monolayer 2H-WSe 2 are calculated respectively. It is expected that the research in our work will provide some theoretical guidance for the application of 2H-WSe 2 in the field of optoelectronics. • Originality and Novelties: Our results show that doping Ti, Nb, and Ni atoms can effectively enhance the photocurrent and extinction ratio of the monolayer 2H-WSe 2 . The photocurrent functions are all proportional to COS2θ. The Ni-doped system can obtain the largest photocurrent (1.484) and the extinction ratio (23.2), which are mainly attributed to the fact that the doping introduces multiple impurity energy bands, which becomes a bridge for electronic transitions.

Superior UV photodetector performance of TiO2 films using Nb doping

Titanium dioxide (TiO2) is one of the excellent materials used for photodetector applications due to its high photoactive nature. In this research, highly sensitive ultra-violet (UV) photodetectors with high detectivity and external quantum efficiency (EQE) are developed by depositing Nb-doped TiO2 (TNO) films onto a Si/SiO2 substrate at different Nb concentrations. The doping effect of Nb on the electronic structure and photodetector performance of TiO2 films has been investigated. The charge compensation mechanism due to Nb-doping has been explained using X-ray photoelectron spectroscopy. Lower doping concentrations of Nb5+ result in creating a Ti vacancy and an excess electron per Nb atom, contributing to the enhanced photocurrent. The metal-semiconductor-metal (M-S-M) structure of the device generates an ohmic-contact and the Si/SiO2 layer assisted toward reducing the surface recombination. All these factors cause an enhancement in the photocurrent, detectivity, and EQE of the TNO photodetector. Finally, the optimized TNO film grown using 1.0 at.% Nb shows improved photodetector properties and is suitable for ultra-sensitive UV photodetector applications.

Effect of added stabilizing elements on thermal activation process of plastic deformation in 18Cr ferritic stainless steel

The effects of a trace amount (~0.1 at.%) of added stabilizing elements (Nb, Ti, and Zr) on the tensile properties of 18Cr ferritic stainless steel sheets at strain rates ranging from 10−3–102 s−1 (from ordinary quasi-static deformation to dynamic deformation) were investigated. The additional Ti or Zr elements formed coarse carbide or nitride precipitates, which consumed interstitial solute elements (C and/or N) in the ferrite matrix. In the Nb-added steel, however, only fine NbN precipitates with a few hundred nanometers in size were observed locally, implying a small amount of solute Nb in the ferrite matrix. Ti or Zr additions had only a slight effect on the deformation resistance of 18Cr ferritic steel sheets and strain rate sensitivity (m) of the flow stress, however, the Nb addition increased the deformation resistance and significantly reduced the strain rate sensitivity. The measured activation volume (v*) values of the Ti- and Zr-added steels (62 b3 and 66 b3) were almost equivalent to one of the 18Cr base steel (64 b3). This result suggested that a general thermally activated process for screw dislocation motion is controlled by double-kink nucleation, which is slightly affected by Ti or Zr additions. The high v* value (106 b3) of the Nb-added steel indicated that the thermally activated process of plastic deformation would be associated with the substitutional solute Nb atoms (act as short-range obstacles) interacting with the moving dislocations. These results showed that the Nb element played a distinct role in plastic deformation from the other stabilizing elements of Ti and Zr.