Ab Initio Study of Binary and Ternary Nb3(X,Y) A15 Intermetallic Phases (X,Y = Al, Ge, Si, Sn)

Abstract

Elastic and thermodynamic properties of binary and ternary A15 phases containing Al, Ge, Si and Sn were studied using the first-principles pseudopotential plane-wave method based on density functional theory. The temperature dependence of the enthalpy of formation for the A15 intermetallics is reported using the quasiharmonic approximation. Elastic properties of the studied compounds were calculated at T = 0 K and were in agreement with the measured values reported in the literature. The elastic properties and thermodynamic data for the metastable A15-Nb 3 Si are reported for the first time. The Nb 3 Si has the highest bulk, shear and Young's modulus values and is predicted to be less ductile than the other three binary A15 intermetallics. The calculations suggest (i) that Al and Sn have a positive effect on the ductility of the A15 compounds of this study, (ii) that Ge as a ternary addition has a ductilizing effect only in the A15-Nb 3 Si, and (iii) that Si as a ternary addition has a negative effect on the ductility of all the A15 compounds of the present study. The linear thermal expansion coefficients of the Nb, Al, the A15 Nb 3 Al, Nb 3 Ge, Nb 3 Sn and Nb 3 Si (A15) phases are reported. The Sn and Al additions in the Nb 3 Si stabilise the A15 structure, while the Ge addition has the opposite effect, stabilising the tP32 Nb 3 Si. * Corresponding author: p.tsakiropoulos@sheffield.ac.uk, fax +440(0)1142225943

Insight into Physical and Thermodynamic Properties of X3Ir (X = Ti, V, Cr, Nb and Mo) Compounds Influenced by Refractory Elements: A First-Principles Calculation

“…Such a result is in good compliance with the Cauchy pressure of Ti 3 Ir provided by Rajagopalan [34]. Similarly, other A15 cubic crystals (i.e., V 3 X (X = Si and Ge) [13], Nb 3 X (X = Al, Ge, Si and Sn) [10] and Nb 3 X (X = Al, Ga, In, Sn and Sb) [42]) have ductile characters owing to their positive Cauchy pressures.…”

“…For example, Pan et al [9] reported the mechanical and electronic properties of Nb 3 Si using the first-principles method. By combining the first-principles method with quasi harmonic approximation, Papadimitriou et al [10][11][12] critically investigated the mechanical and thermodynamic properties of Nb 3 X (X = Al, Ge, Si and Sn). Chihi et al [13] theoretically evaluated the elastic and thermodynamic properties of V 3 X (X = Si, Ge and Sn) intermetallics utilizing the first-principles calculations.…”

Insight into various properties of rare‐earth–based inverse perovskites Gd 3 AlX (X = B, N)

“…Moreover, the modification in crystal structure can be determined using strain tensor ε ij. The generalized form of Hook's law, relating these two tensors, is given as σ ij = C ijkl ε kln , where the quantity C ijkl ε kl characterize the stiffness of material . The elastic constants are fundamentally important under different conditions because they provide worthy knowledge about mechanical steadiness and binding characteristics .…”

“…The generalized form of Hook's law, relating these two tensors, is given as σ ij = C ijkl ε kln , where the quantity C ijkl ε kl characterize the stiffness of material. 37 The elastic constants are fundamentally important under different conditions because they provide worthy knowledge about mechanical steadiness and binding characteristics. 38 The elastic constants are computed by energy-strain relation; this is done by applying strains in small amounts to the equilibrium structure and analyzing the change in the total energy.…”

Alloying and Properties of C14–NbCr2 and A15–Nb3X (X = Al, Ge, Si, Sn) in Nb–Silicide-Based Alloys

“…The properties of unalloyed A15–Nb 3 X (X = Al, Ge, Si, Sn) intermetallics that can form in Nb–silicide-based alloys were studied in [ 28 , 30 , 31 , 32 , 33 ]. The moduli of elasticity of A15 intermetallics are not unusually high.…”