“…[ 24 ] The calculated elastic constants C ij for RuVAs and RuNbAs alloys in α phase are summarized in Table 2 . Our calculated values obtained by using the Thomas Charpin method integrated in the Wien2k code [ 15 ] differ slightly from those found by Chibani et al, [ 20 ] who used the IRelast method. The calculated elastic constants satisfy the stability conditions, which implies that these materials are mechanically stable.…”
Density functional (DFT) theory and semiclassical Boltzmann theory are used to calculate structural, mechanical, electronic, and transport properties of RuVAs and RuNbAs half‐Heusler alloys. The band structure calculations reveal a p‐type semiconducting state with narrow indirect (L–X) gap values of 0.20 and 0.36 eV for RuVAs and RuNbAs alloys, respectively. The Seebeck coefficient S, electrical conductivity σ, thermal conductivity κe, and figure of merit ZT are calculated in the temperature range 100–1200 K. The lattice thermal conductivity κL and the relaxation time τ are also determined. At room temperature, RuVAs and RuNbAs alloys exhibit ZT values of 0.22 and 0.30 respectively, which correspond to the lattice thermal conductivity κL equal to 18.67 and 15.14 W m−1 K. κL rapidly decreases with increasing temperature. In addition, the maximum value of ZT reaches 0.47 at 900 K and 0.62 at 1000 K for RuVAs and RuNbAs alloys, respectively. Consequently, these compounds could be a candidate for use as p‐type thermoelectric materials operating at high temperatures.
“…[ 24 ] The calculated elastic constants C ij for RuVAs and RuNbAs alloys in α phase are summarized in Table 2 . Our calculated values obtained by using the Thomas Charpin method integrated in the Wien2k code [ 15 ] differ slightly from those found by Chibani et al, [ 20 ] who used the IRelast method. The calculated elastic constants satisfy the stability conditions, which implies that these materials are mechanically stable.…”
Density functional (DFT) theory and semiclassical Boltzmann theory are used to calculate structural, mechanical, electronic, and transport properties of RuVAs and RuNbAs half‐Heusler alloys. The band structure calculations reveal a p‐type semiconducting state with narrow indirect (L–X) gap values of 0.20 and 0.36 eV for RuVAs and RuNbAs alloys, respectively. The Seebeck coefficient S, electrical conductivity σ, thermal conductivity κe, and figure of merit ZT are calculated in the temperature range 100–1200 K. The lattice thermal conductivity κL and the relaxation time τ are also determined. At room temperature, RuVAs and RuNbAs alloys exhibit ZT values of 0.22 and 0.30 respectively, which correspond to the lattice thermal conductivity κL equal to 18.67 and 15.14 W m−1 K. κL rapidly decreases with increasing temperature. In addition, the maximum value of ZT reaches 0.47 at 900 K and 0.62 at 1000 K for RuVAs and RuNbAs alloys, respectively. Consequently, these compounds could be a candidate for use as p‐type thermoelectric materials operating at high temperatures.
“…Figure 1 shows the convergence of the lattice constant for RuVBi, RuVSb and RuVAs half-Heuslers. Our calculated values for lattice constants, bulk modulus and the pressure derivative of B are represented in Table 1 alongside with results obtained from both theoretical computations [50,51] and experiment [52]. For the first time, we have obtained results for the lattice constant, bulk modulus, and its derivative as 6.18 Å, 143.35 GPa and 5.14 respectively, for RuVBi half-Heusler.…”
Section: Structural and Electronic Propertiesmentioning
Half-Heusler (hH) alloys are an intriguing class of materials with significant potential for applications in spintronics, thermoelectrics, optoelectronics, and magnetoelectronics due to their unique adjustable properties. In this work, we have investigated the structural, thermodynamic, mechanical, and electronic properties of RuVZ (Z: As, Bi, Sb) half-Heusler materials using the density functional theory (DFT) as implemented in the quantum espresso computational suite. The structural, thermodynamic, and mechanical properties were also predicted using the linear response density functional perturbation theory. We observed that the hH alloys are non-magnetic semiconductors and have an indirect narrow band gap. The band gap values and lattice constants for RuVSb and RuVAs cubic crystals are consistent with published reports. RuVBi has a lattice constant of 6.18 and a band gap of 0.16 eV. The elastic parameter results obtained satisfy Born's stability requirements, suggesting mechanical stability of the hH materials. All three alloys are found to be ductile. The RuVZ alloys obey the Dulong-Petit law at heat capacity of 74.7, 74.5, and 74.3 J mol-1K-1 and temperatures of 556, 754, and 775 K, respectively. The Debye temperature of 353.75K suggests that the RuVAs alloy is the hardest, with a significant Debye sound velocity (2997.12 m/s) and will have high thermal conductivity.
Heusler alloys have been a significant topic of research due to their unique electronic structure, which exhibits half-metallicity, and a wide variety of properties such as magneto-calorics, thermoelectrics, and magnetic shape memory effects. As the maturity of these materials grows and commercial applications become more near-term, the mechanical properties of these materials become an important factor to both their processing as well as their final use. Very few studies have experimentally investigated mechanical properties, but those that exist are reviewed within the context of their magnetic performance and application space with specific focus on elastic properties, hardness and strength, and fracture toughness and ductility. A significant portion of research in Heusler alloys are theoretical in nature and many attempt to provide a basic view of elastic properties and distinguish between expectations of ductile or brittle behavior. While the ease of generating data through atomistic methods provides an opportunity for wide reaching comparison of various conceptual alloys, the lack of experimental validation may be leading to incorrect conclusions regarding their mechanical behavior. The observed disconnect between the few available experimental results and the numerous modeling results highlights the need for more experimental work in this area.
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