Mechanics, Materials Science & Engineering, July 2017 – ISSN 2412-5954
Theoretical Investigation on the Structural, Elastic and Mechanical Properties of Rh3HxNb1-x(x=0.125, 0.875) 1
M. Manjula1, M. Sundareswari1 1 – Department of Physics, Sathyabama University, Chennai, India DOI 10.2412/mmse.86.89.465 provided by Seo4U.link
Keywords: first-principles theory, density functional theory, electronic properties, mechanical properties, ductility.
ABSTRACT. Electronic, elastic and mechanical properties of Rh3HxNb1-x(x=0.125, 0.87) are investigated from density functional theory using FP-LAPW method within generalized gradient approximations. The lattice parameters and ground state properties are calculated by using optimization method. Shear modulus, Young’s modulus, Poisson’s ratio, G/B ratio and anisotropy factor are calculated using elastic constants C11, C12 and C44. The calculated results are consistent with available theoretical and experimental data. Systematic addition of Hf with Rh3Nb shows that the Rh3Hf0.125Nb0.875 and Rh3Hf0.875Nb0.125 are ductile. Charge density plots assess the results.
Introduction. L12 intermetallic compounds such as rhodium and iridium based compounds are of great interest in industrial applications [1], [2]. The mechanical and thermal findings on rhodium base alloys are more convenient for high-temperature structural applications than iridium base alloys. Rhodium is most frequently used as an alloying agent in other materials such as platinum and palladium. These alloys are used to make electrodes for aircraft spark plugs, detectors in nuclear reactors, laboratory crucibles and furnace coils. It has higher thermal conductivity, high temperature strength, good oxidation resistances and lower thermal expansion coefficient which are beneficial properties for high temperature applications [3], [4], [5], [6], [7], [8], [9]. The L12 crystal structure offers the possibility of enhanced ductility and workability of these materials. This motivates us to focus our research on rhodium base alloys. Especially, we focus our attention to design new materials with enhanced ductility from existing one. Alloying is one of the effective ways to attain our aim. To our best knowledge no systematic study on Rh3HfxNb1-x ternary alloy system. We have already reported Rh3HfxNb1-x (x= 0.25.0.75) combinations in our previous work [10]. In the present study, a first-principles calculation based on the density-functional theory was carried to investigate the electronic structure and mechanical properties of Rh3HfxNb1-x (x= 0.125.0.875) combinations. The ductile/brittle nature of these compounds is analysed. A number of theoretical and experimental structural have been performed for structural, electronic, elastic and mechanical properties of Rh3Nb. Yamabe et al. investigated the microstructure evolution and high temperature strength of Rh-based alloys [11]. Rajagopalan and Sundareswari reported structural and electronic properties of this compound [12]. Chen et al. [13] investigate elastic and mechanical properties of this compound. The mechanical properties of Rh3Nb are studied by Miura et al. [14]. Some of the thermal properties were measured by Terada et al. [15]. Their strength behaviour was discussed by Yamabe-Mitarai et al. [16] Computational Methods. Our calculations are carried out by means of Full Potential Linearized Augmented Plane wave (FP-LAPW) method implemented in the WIEN2k code [17]. The basis set is obtained by dividing the unit cell into non-overlapping spheres surrounding each atom and creating an interstitial region between the spheres. The exchange and correlation was treated within the generalized gradient approximation by Perdew et al [18]. 10×10×10 k-point mesh is used in the 1
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