Entire Composition Range Research Articles

Thermodynamic properties, viscosity modelling and FTIR studies of binary liquid mixtures of 2-isopropoxy ethanol with amines at different temperatures

Thermodynamic and spectral analysis for binary liquid mixtures of 2-isoporopxy ethanol with diisopropylamine, di-n-butylamine and tri-n-butylamine has been carried out in the present discussion. For this purpose, measurements of density, speed of sound and viscosity for binary mixtures were carried out over the entire composition range and at temperatures (298.15, 303.15 and 308.15) K. Various excess and deviation parameters were evaluated using the measured properties. Behaviour of calculated parameters was found quite sensitive towards the intermolecular interactions. Change in behaviour of these parameters with composition and temperature has been discussed in terms of intermolecular interactions due to physical and chemical effects among unlike molecules. Excess parameters were correlated with composition using Redlich-Kister polynomial. Existing theories and semi-empirical relations for viscosity were tested. Spectroscopic methods were also utilized to support the results obtained from above calculated parameters qualitatively.

Density Functional Tight-Binding Model for Lithium-Silicon Alloys.

The predictive power of molecular dynamic simulations is mainly restricted by the time scale and model accuracy. Many systems of current relevance are of such complexity that they require addressing both issues simultaneously. This is the case of silicon electrodes in Li-ion batteries, where different LixSi alloys are formed during charge/discharge cycles. While first-principles treatments for this system are seriously limited by the computational cost of exploring its large conformational space, classical force fields are not transferable enough to represent it accurately. Density Functional Tight Binding (DFTB) is an intermediate complexity approach capable of capturing the electronic nature of different environments with a relatively low computational cost. In this work, we present a new set of DFTB parameters suited to model amorphous LixSi alloys. LixSi is the usual finding upon cycling the Si electrodes in the presence of Li ions. The model parameters are constructed with a particular emphasis on their transferability for the entire LixSi composition range. This is achieved by introducing a new optimization procedure that weights stoichiometries differently to improve the prediction of their formation energies. The resulting model is shown to be robust for predicting crystal and amorphous structures for the different compositions, giving excellent agreement with DFT calculations and outperforming state-of-the-art ReaxFF potentials.

Insight to the Local Structure of Mixtures of Imidazolium-Based Ionic Liquids and Molecular Solvents from Molecular Dynamics Simulations and Voronoi Analysis.

While the physicochemical properties as well as the NMR and vibration spectroscopic data of the mixtures of ionic liquids (ILs) with molecular solvents undergo a drastic change around the IL mole fraction of 0.2, the local structure of the mixtures pertaining to this behavior remains unclear. In this work, the local structure of 12 mixtures of 1-butyl-3-methylimidazolium cation (C4mim+) combined with perfluorinated anions, such as tetrafluoroborate (BF4-), hexafluorophosphate (PF6-), trifluoromethylsulfonate (TFO-), and bis(trifluoromethanesulfonyl)imide, (TFSI-), and aprotic dipolar solvents, such as acetonitrile (AN), propylene carbonate (PC), and gamma butyrolactone (γ-BL) is studied by molecular dynamics simulations in the entire composition range, with an emphasis on the IL mole fractions around 0.2. Distributions of metric properties corresponding to the Voronoi polyhedra of the particles (volume assigned to the particles, local density, radius of spherical voids) are determined, using representative sites of the cations, anions, and the solvent molecules, to characterize the changes in the local structure of these mixtures. By analyzing the mole fraction dependence of the average value, fluctuation, and skewness parameter of these distributions, the present study reveals that, around the IL mole fraction of 0.2, the local structure of the mixture undergoes a transition between that determined by the interionic interactions and that determined by the interactions between the ions and solvent molecules. It should be noted that the strength of the interactions between the ions and the solvent molecules, modulated by the change in the composition of the mixture, plays an important role in the occurrence of this transition. The signature of the change in the local structure is traced back to the nonlinear change of the mean values, fluctuations, and skewness values of the metric Voronoi polyhedra distributions.

Computer simulation study of ion-water and water-water hydrogen bonds in methanesulfonic acid solutions at room temperature

Classical molecular dynamics simulations of aqueous methanesulfonic acid solutions have been conducted at room temperature in the entire composition range. The dissociation of the acid has been considered according to the available experimental data. Then, the systems are constituted by the following molecular species: water and methanesulfonic acid molecules, hydronium cations, and mesylate anions. The simulations have been carried out employing a reliable force field, which provides density values that show an excellent agreement with the available experimental data. The shear viscosity, the diffusion coefficients of the molecular species, and the radial distribution functions, which involve water molecules, have also been computed. We have observed that water molecules diffuse faster than the other species at all concentrations. Moreover, the shear viscosity and the diffusion coefficients exhibit a noticeable unimodal concentration dependence with extrema located at 90 wt% (0.628 mol fraction). A detailed hydrogen bond analysis, concerning water molecules, has also been made. At low dilutions, water exhibits its well-known hydrogen bond tetrahedral structure, which vanishes as the acid concentration increases. The most labile water molecules are those bonded to the anions. At large concentrations, the lability of the water molecules, bonded to other water molecules, increases, and that of the water molecules, bonded to the cations, decreases. The interrupted lifetimes also show a unimodal dependence with maxima located at 90 wt%. This behavior could be related to the appearance of the methanesulfonic acid hydrogen bond network, which emerges at large weight percentage values because the acid almost completely dissociates up to concentrations of 70 wt% (0.304 mole fraction).

Density, Speed of Sound, and Refractive Index Data for Oct-1-ene (1) + Propan-1-ol (2)/Propan-2-ol (2) Mixtures at T = (298.15–338.15) K and 0.101 MPa

Density, speed of sound, and refractive index measurements were conducted for the systems oct-1-ene + propan-1-ol/propan-2-ol over the entire composition range at temperatures of T = (298.15, 308.15, 318.15, 328.15, and 338.15) K and at atmospheric pressure, 0.101 MPa. It was discovered that these characteristics showed nonlinear relations with composition, indicating that the mixtures behave nonideally. From the experimental data, derived thermophysical behaviors were obtained by calculation for excess molar volume, deviation in speed of sound, excess isentropic compressibility, deviation in thermal expansivity, and deviation in refractive index. The excess molar volumes were found to be positive over the entire composition range for both systems, with the oct-1-ene + propan-2-ol system exhibiting a larger deviation from ideal volume mixing behavior in comparison to the oct-1-ene + propan-1-ol system. A systematic increasing trend with temperature was observed. The deviation in speed of sound exhibited a nonlinear trend with composition and is positive over the entire composition range. The excess isentropic compressibility exhibited transitional behavior from positive to negative. At temperatures below 328.15 K, a negative deviation in refractive index was observed for both systems for the entire composition range; however, as the temperature increased, a positive deviation is observed in the octene-rich region for the propan-2-ol systems. The excess/deviation properties were correlated by the Redlich–Kister polynomial.

Thermodynamic study of binary mixtures of propilophenone + 2-propanol, 2-butanol, 2-pentanol, or 2-hexanol at temperatures of 293.15 to 323.15 K: Modeling by Prigogine-Flory-Patterson theory

In the present work, the density and viscosity of binary mixtures of propiophenone (PP) + 2-propanol, PP + 2-butanol, PP + 2-pentanol, or PP + 2-hehanol were measured over all composition range and in the temperature range of 293.15 to 323.15 K at ambient pressure (0.1 MPa). Using the experimental data of density and viscosity, the excess molar volume and viscosity deviation were calculated and correlated by applying the Redlich-Kister equation. The results show that the excess molar volume of all mixtures is negative over the entire composition range at all temperatures and become more negative with increasing temperature. Also, the viscosity deviation of all mixtures is negative over the whole composition range at all temperatures and become less negative with increasing temperature. The excess molar volumes of mixtures were correlated by using Prigogine-Flory-Patterson (PFP) theory and the agreement between the calculated values with experimental data is good.

Solubility, Diffusivity, and Permeability of HFC-32 and HFC-125 in Amorphous Copolymers of Perfluoro(butenyl vinyl ether) and Perfluoro(2,2-dimethyl-1,3-dioxole)

R-410A, an azeotropic mixture composed of 50 wt % difluoromethane (HFC-32, CH2F2) and 50 wt % pentafluoroethane (HFC-125, CHF2CF3) used in residential and commercial air-conditioning applications, will be phased down due to the high global warming potential (GWP) of HFC-125. The HFC-32 can be reused in low-GWP blends containing hydrofluoroolefins (HFOs); however, incumbent separation technology, fractional distillation, cannot separate azeotropic mixtures. Membrane technology provides the opportunity to achieve a selective separation of azeotropic HFC refrigerant mixtures with lower energy consumption and capital requirements. This study explores the use of amorphous perfluoropolymers for the separation of R-410A. The permeability, solubility, and diffusivity of HFC-32 and HFC-125 were measured in copolymers of perfluoro(butenyl vinyl ether) (PBVE) and perfluoro(2,2-dimethyl-1,3-dioxole) (PDD). Pure gas permeability of HFC-32 and HFC-125 were measured using a static membrane apparatus and the pressure-rise method. Solubility measurements were obtained using a gravimetric microbalance, and diffusivity was calculated using a Fickian model. The results indicate that a high permeability and selectivity of HFC-32/HFC-125 can be obtained with a 50 wt % PBVE and 50 wt % PDD copolymer and that the separation is diffusion-driven over the entire range of compositions tested.

Measurement and correlation of diffusion coefficients of vitamin K3 in a fluid mixture of carbon dioxide and decane at 313–343 K and 10–30 MPa

The diffusion coefficients D1m of vitamin K3 in a dense fluid mixture of carbon dioxide and decane were measured by the Taylor dispersion method at temperatures from (313.2–343.2) K and pressures from (10−30) MPa, over the entire range of decane composition. The D1m values of vitamin K3 increased with increasing temperature and decreasing pressure under isocratic conditions. In addition, the measured D1m values were found to be correlated with the hydrodynamic (HD) equation based on the Stokes–Einstein equation, with an average relative deviation of 4.9% for 110 conditions over a wide range of fluid viscosities ranging from that of supercritical carbon dioxide to that of compressed liquid decane, apparently irrespective of the decane composition and solvent species.

Optical studies of binary mixture containing palm biodiesel and alkanols : experimental and theoretical interpretation

Refractive indices (nD ) of binary mixture containing palm biodiesel (P) and alkanols (1-pentanol (1P) and 3-pentanol (3P)) were measured at different temperatures (298.15,303.15k,308.15k,313.15k,318.15k) at 0.1 MPa over the entire composition range of mole fractions. The nD values of pure compounds and their binary mixtures were measured by using refractometer (Anton Paar Abbemat 200). Experimental data of nD were used to compute deviation in refractive index (Δn). Further, refractive index values also have been measured in terms of different mixing rules like Lorentz-Lorentz (L.L), Gladstone-Dale (G.D), Heller-relation (H.R) and Weiner-relation (W.R). The experimental data of nD compared well with the values obtained by using mixing rules for binary mixture P (1) + Alkanols (2). The measured data were correlated by Redlich-Kister polynomial equation. The effect of temperature has also been investigated.

Volumetric and Spectroscopic Studies of 1-ethyl-3-methylimidazolium Ethylsulfate/Propane-1-ol Binary Mixtures at Different Temperatures

Binary mixtures of an ionic liquid, 1-ethyl-3-methylimidazolium ethyl sulfate ([C2mim]C2H5SO4) with propane-1-ol were prepared over an entire composition range and density, dynamic viscosity, and refractive index at T = 293.15 to T = 333.15 K at atmospheric pressure were measured. The excess properties for the binary systems were determined and successfully fitted to a polynomial equation of the Redlich–Kister type. The variation of excess thermodynamic parameters predicted stronger intermolecular interactions and effective packing in the binary system compared to components. Thermodynamic activation parameters were also calculated from the Eyring equation, which varied with the concentration of [C2mim]C2H5SO4. The variation of these parameters also suggested the presence of strong heteromolecular interactions. The near-infrared (NIR) spectroscopic measurements were conducted in the temperature range from 293.15 K to 333.15 K and spectral variations were analyzed. The NIR data were further evaluated using principal component analysis (PCA) and two-dimensional (2D) correlation spectroscopy. The predicted molecular-level interactions mainly come from different types of HBs formed between unlike molecules in the binary system. The binary mixture may open up a plethora of possible uses due to its novel, distinctive molecular-level interactions, and favorable thermodynamic properties.

A comprehensive study on the thermodynamics of the Al13Fe4 solid solution in the Al-Fe-Mn ternary system

This paper presents investigations on the thermodynamic stability of the Al13Fe4 solid solution in the Al-Fe-Mn ternary system as well as its crystal chemistry characterisation. In order to carry out this study, the isobaric heat capacity of the solution was measured at high temperature using a high precision three-dimensional probe. The heat capacity of the Al13Fe4 binary compound measured in this study between 600 K and 1223 K is CP(T) = 23.97 + 8.18.10−2T − 7.63.105T2. This value is significantly different from other measurements reported in the literature. We show in this paper that our measurements are more accurate than those available in the literature thanks to the use of a more precise sensor (3D-Cp sensor versus planar DSC sensor). As a result, our measurements are more thermodynamically consistent with the enthalpy of formation values of the Al13Fe4 compound available in the literature, as well as with our own enthalpy of formation measurement performed independently of the heat capacity measurement presented in this paper. Measurements of the enthalpy of formation of the solid solution were also performed by in-situ synthesis in a DSC. These new measurements were complemented by DFT calculations of the enthalpy of formation at 0 K of the solid solution. Our calculations and measurements show that the substitution of Fe by Mn is responsible for a large increase in the solid solution enthalpy of formation. These new experimental and calculated data were used to develop a thermodynamic model of the solution. Finally, we utilized our model to calculate the Fe site occupation factors (sof) of the solid solution structure over its entire chemical composition range (simulating the complete substitution of all Fe atoms with Mn) as a function of temperature. The chemical ordering of the solid solution was thus quantified, revealing its ideal nature near its melting temperature. These results allowed the development of a new SL-model for the solution, both simpler and more reliable than those used in the literature.

Phase equilibria in the YbCl2–MCl (M = Li, Na, K) binary systems

Differential scanning calorimetry technique was used to investigate phase equilibria in the YbCl2–MCl (M = Li, Na) binary systems. The YbCl2–LiCl system exhibits an eutectic located at YbCl2 mole fraction x = 0.415 (733 K) and a LiYb2Cl5 stoichiometric compound that is formed at 711 K and melts incongruently at 742 K. The YbCl2–NaCl system exhibits an eutectic located at YbCl2 mole fraction x = 0.559 (764 K). In both systems the formation of solid solutions in the MCl-rich side (M = Li, Na) has been found. The molar enthalpies of mixing (ΔHMIX) in the liquid YbCl2–MCl (M = Na, K) mixtures have been measured at 1085 K with a Calvet-type high temperature microcalorimeter in the entire range of composition. A negative value of mixing enthalpy was observed for all melts. The minimum value was of approximately: − 2.5, and − 7.5 kJ mol−1, for systems with NaCl and KCl, respectively. All the experimental results along with the available literature data were used to optimize the thermodynamic properties of the investigated systems using the CALPHAD method.

Composition-Tuned (MoWV)Se2 Ternary Alloy Nanosheets as Excellent Hydrogen Evolution Reaction Electrocatalysts

Ternary alloying of transition metal dichalcogenides (TMDs) has the potential for altering the electronic structure of materials to suit electrochemical applications. Herein, we synthesized (MoWV)Se2 nanosheets at various compositions via a colloidal reaction. The mole fraction of V atoms (xV) was successfully increased up to 0.8, producing a metallic phase that is highly durable against hydration. Furthermore, we synthesized (MoW)Se2 nanosheets over the entire composition range. The atomic mixing of the ternary alloys is more random than that of the constitutional binary alloys, as supported by first-principles calculations. Compared to binary alloying, ternary alloying more effectively enhanced the electrocatalytic activity for acidic hydrogen evolution reaction (HER). The HER performance increased upon increasing xV to 0.44, and thereafter, it declined at higher xV primarily owing to surface oxidation. The analysis of Gibbs free energy for H adsorption revealed that ternary alloying strongly activates the basal plane for the HER. VSe2 contains numerous sites favorable for H adsorption, facilitating the composition-dependent HER. These results provide a pioneering strategy for designing multicomponent TMD catalysts that maximize the advantages of each component.

Surface Properties of N,N-Dimethylformamide-Water Mixtures, As Seen from Computer Simulations.

The liquid-vapor interface of N,N-dimethylformamide (DMF)-water mixtures, spanning the entire composition range, is investigated in detail at 298 K by molecular dynamics simulation and intrinsic surface analysis. DMF molecules are found to adsorb strongly at the liquid surface, but this adsorption extends only to the first molecular layer. Water and DMF molecules mix with each other on the molecular scale even in the surface layer; thus, no marked self-association of any of the components is seen at the liquid surface. The major surface component prefers such orientation in which the molecular dipole vector lays parallel with the macroscopic plane of the surface. On the other hand, the preferred orientation of the minor component is determined, at both ends of the composition range, by the possibility of H-bond formation with the major component. The lack of H-donating ability of DMF leads to a rapid breakup of the percolating H-bond network at the surface; due to the strong adsorption of DMF, this breakup occurs below the bulk phase DMF mole fraction of 0.03. The disruption of the surface H-bond network also accelerates the exchange of both species between the liquid surface and bulk liquid phase, although, for water, this effect becomes apparent only above a bulk phase DMF mole fraction of 0.4. H-bonds formed by a DMF and a water molecule live, on average, 25-60% longer than those formed by two water molecules at the liquid surface. A similar, but smaller (i.e., about 10-20%) difference is seen in the bulk liquid phase. The enhanced surface mobility of the molecules results in 2-6 times larger diffusion coefficient and 2-5 times shorter H-bond lifetime values at the liquid surface than in the bulk liquid phase. The diffusion of both molecules is slowed down in the presence of the other species; in the case of DMF, this effect is caused by the formation of water-DMF H-bonds, whereas for water, steric hindrances imposed by the bulky DMF neighbors are responsible for this slowing down.

Specific interchain interactions of poly(ethylene 2,5‐furandicarboxylate) with polyglycolide acid blends and its effect on miscibility

AbstractPoly (ethylene 2,5‐furan dicarboxylate) (PEF) with excellent physical properties is considered to be a perfect industrial alternative for PET. In this paper, a series of PEF/PGA blends with different mass ratios were prepared, and the miscibility and interchain‐associated interactions of those blends were studied by differential scanning calorimetry, scanning electron microscopy, nuclear Magnetic Resonance Spectroscopy, FTIR spectroscopy, and wide‐angle X‐ray diffraction. Experiment results suggested that there are two specific interchain‐associated interactions between PEF and PGA, which made those two components have good miscibility over the entire composition range and caused the Tgs of the blends slightly lower than the theoretical value calculated by FOX equation. After sufficiently isothermal crystallized at 160 °C, the primary and secondary contribution of these two interchain‐associated interactions between PEF and PGA in blends is reversed. In other words, the interchain‐associated interactions composed of CO of PGA component and CH2 of PEF component is the primary role, the interchain‐associated interactions composed of CO of PEF component and CH2 of PGA component is the secondary role before isothermal crystallization, after isothermal crystallization, which are reversed.

Steric hindrance affects interactions of poly(styrene–alt–DMHPMI) copolymer with strongly hydrogen-bond-accepting homopolymers

In this study, we synthesized the monomer N-(2,6-dimethylhydroxyphenyl)maleimide (DMHPMI) in three steps from 2,6-dimethylphenol and then reacted it with styrene through free radical copolymerization to prepare the alternating copolymer poly(styrene–alt–dimethylhydroxyphenylmaleimide) [poly(S–alt–DMHPMI)]. We used Fourier transform infrared (FTIR) spectroscopy, 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, and mass-analyzed laser desorption ionization/time-of-flight (MALDI-TOF) mass spectrometry to confirm its structure. Differential scanning calorimetry revealed that blends of the alternating copolymers poly(S–alt–DMHPMI) and poly(styrene–alt–(para–hydroxyphenylmaleimide)) [poly(S–alt–pHPMI)] with the Strongly Hydrogen-Bond-Accepting homopolymers poly(4-vinylpyridine) (P4VP) and polyvinylpyrrolidone (PVP) each exhibited single-value glass transition temperatures (Tg) over the entire compositional range, indicative of full miscibility. Nevertheless, a negative deviation from the linear rule occurred for the Tg behavior of the PS–alt–PHPMI/P4VP blends, due to the weak acidity of the HPMI units, while the intermolecular interactions of the PS–alt–PHPMI coplymers were also inhibited because of strong self-association of the PHPMI units. FTIR spectral analyses of the ratio of hydrogen-bonded OH and pyridyl groups confirmed this behavior. In contrast, slightly positive deviations from the linear rule occurred for the Tg behavior when blending poly(S–alt–DMHPMI) or poly(S–alt–pHPMI) with the PVP homopolymer; here, the intermolecular interactions of the poly(S–alt–DMHPMI)/PVP blends were weaker than those of the poly(S–alt–pHPMI)/PVP blends, due to the steric hindrance of the DMHPMI units being greater than that of the pHPMI units.

Thermodynamic and spectral studies of molecular interactions in binary liquid mixtures of 1-butoxy-2-propanol with amines at different temperatures

ABSTRACT Binary liquid mixtures of 1-butoxy-2-propanol with amines namely diethylamine, dipropylamine and triethylamine have been discussed in the present discussion. Measurements of density and speed of sound of pure liquids and their binary mixtures have been carried out over the entire composition range and temperatures (298.15, 303.15 and 308.15) K. To study the thermodynamic behaviour of these liquid mixtures, various parameters were calculated using the experimentally measured data. Strong intermolecular interactions among the components of binary liquid mixtures were confirmed by calculated parameters. Various excess and deviation properties were correlated to composition using the Redlich–Kister polynomial. Further, density and speed of sound data were correlated with composition using Jouyban–Acree model. The experimental results have been analysed by using Prigogine–Flory–Patterson (PFP) theory. 1H-NMR spectra of binary mixtures at equimolar composition has also been studied.

Viscosity of molten Cu–M alloys (M = Ni, Al)

The viscosities of the molten Cu–Ni and Cu–Al alloys were measured using an oscillating crucible method over the entire composition range to obtain reliable data and examine composition dependence precisely. The measured viscosities of all alloys showed good consistency in heating and cooling processes, and the logarithmic viscosities showed good Arrhenius-type linearity, indicating that no considerable change in the liquid structure occurs in the temperature range studied. The composition dependence of the viscosity of Cu–Ni alloys was close to that defined by the additive law of logarithmic viscosities of pure components, whereas the composition dependence of the viscosity of Cu–Al alloys was far from that defined by the additive law, where the logarithmic viscosity increased with the addition of a small amount of Al and showed a peak. Over the peak concentration, the logarithmic viscosity monotonically decreased with further addition of Al. Deviations from the additive law of logarithmic viscosity of molten Cu–Al alloys at 1773 K were maximum at low Al concentrations; in contrast, the excess molar volumes of Cu–Al alloys showed minimum at low Al concentrations. The increase in viscosity in the low-Al-concentration region of the Cu–Al alloy is attributed to the decrease in the interatomic distance, which reduces the freedom of movement of atoms.

Kinetic studies on acidic wet chemical etching of silicon in binary and ternary mixtures of HF, HNO3 and H2SiF6.

The etching of silicon with mixtures of hydrofluoric acid (HF), nitric acid (HNO3) and hexafluorosilicic acid (H2SiF6) proceeds in a complex reaction scenario consisting of interacting side reactions. Almost no other dissolution reaction is so massively dependent on the reaction conditions that influence the etching rate and the mechanism of the individual reactions. Extensive studies of the reaction rate of silicon etching in binary and ternary acid mixtures have allowed the transition point between the reaction-controlled and diffusion-controlled reaction regimes to be determined as a function of the composition of the etching mixture. It was verified that the reaction mechanism for binary and ternary mixtures does not differ and only the lower water content in ternary mixtures favours an enhanced formation of the reactive N(III) intermediate HNO2 in side reactions. Based on the exact knowledge of the point of mechanism change, determination of the reaction rate under quasi-isothermal conditions in the bulk etching range allows, for the first time, deriving formal kinetic terms from the kinetic data to describe the dissolution rate in both the reaction-controlled and diffusion-controlled regimes. The formal kinetic terms were designed both for the kinetically correct quasi-isothermal approach to the dissolution rate in the Si bulk and for the application-oriented approach that includes induction phases and temperature increases in the considered dissolution period as well as influences of the surface properties. Moreover, by using the water content of the etching mixtures as a proxy variable, uniform calculation of the etching rates in HF/HNO3 as well as in HF/HNO3/H2SiF6 mixtures in the entire composition range of the application can be formulated.

The effect of systematic substitution of Nb with Ti on a potential high-temperature shape memory alloy: B2 NbRu

NbRu has been considered as a potential high-temperature shape memory alloy due to its high martensitic transformation temperature, however, it has poor superelasticity and other shape memory properties, which limits its applications. In this paper, the effect of systematic substitution of Nb with Ti on the structural, thermodynamic, and elastic properties of supercell 2x2x2 B2 Ru50Nb50-xTix spanning the entire composition range (x = 0, 6.25, 12.50, 18.75, 25.00, 31.25, 37.50, 43.75, 50 at. %) is investigated using ab initio calculations. Elasticity results showed that the mechanical stability of the B2 phase improved with increasing Ti content, which could be associated with a decrease in transformation temperature. However, a suitable composition range within which Cʹ~0, resembling that of well-known TiNi, is identified. This predicts Ti addition to be effective in improving shape memory properties of B2 NbRu alloy.