Electronic structure and elastic properties of theNi3X(X=Mn, Al, Ga, Si, Ge) intermetallics

Abstract

First-principles total-energy electronic structure calculations based on the full-potential linear-muffin-tinorbital method have been used to study the electronic and mechanical properties of the L1 2-type ordered nickel-based intermetallics Ni 3 X ͑XϭMn, Al, Ga, Si, Ge͒. The calculated values for the equilibrium volume and elastic properties are generally in good agreement with experiments. The large shear anisotropy factor across the series is attributed to the anisotropy of the bonding charge density, which can be described by the combination of charge transfer from X to Ni and strong X p-Ni d ͑Mn d-Ni d in Ni 3 Mn͒ hybridization effect. The more pronounced directional bonding between the Ni and Si atoms compared to that between the Ni and Al atoms, and the small ͑large͒ redistribution of bonding charge in Ni 3 Al ͑Ni 3 Si͒ when the systems are under shear strain result in a stronger resistance to a shear for Ni 3 Si. The bonding charge densities for Ni 3 Ga and Ni 3 Ge are found to be similar to those for Ni 3 Al and Ni 3 Si, respectively. These results suggest that the addition of the extra p electron on the X atom increases the directionality of the bonding. The change of bonding charge directionality in Ni 3 Mn is due to the Mn d-Ni d hybridization. The calculated ratio of bulk to shear modulus of polycrystalline systems, B/G, proposed by Pugh to provide a simple rule of measuring the ease of plastic deformation, is found to correlate well with the absolute difference in the s-orbital electronegativity between the atomic constituents, and the difference in energy, E d ͑Ni͒ϪE p (X) ͓E d ͑Ni͒ϪE d ͑Mn͒ for Ni 3 Mn͔, across the series. ͓S0163-1829͑96͒01443-9͔

Biaxial strain effects on adatom surface diffusion on tungsten from first principles

“…A strain tensor is applied on the computational cell as 40 : ε 33 = ε 12 = ε 13 = ε 23 = 0, while ε 11 and ε 22 are independently changed from -0.02 to 0.02. Since we chose orthogonal supercells, we simply change the lengths of a N 1 × N 2 supercell along the [100] and [010] directions as a 1 = a 0 ε 11 , and a 2 = a 0 ε 22 , where a 0 = 3.165Å is the strain-free single lattice constant, and a 1 , a 2 are the corresponding strained lattice constant.…”

Influence of Si Addition on Microstructure Evolution of Ni<SUB>3</SUB>Al<SUB>0.50</SUB>V<SUB>0.50</SUB> Alloy

“…The yellow cell represents a unit of the L1 2 configuration in the plane, and the A and B sites correspond to the face-centered and corner sites in the unit, respectively. For simplicity, Al, V, and Si are located at the B sites 9,10) in the diagram, while the vacancies are preferentially located at the A sites, 11) and antisite defects are ignored. The directional migration of Al (thick blue arrow) and V (thick green arrow) is considered for the occurrence of the phase separation within the distribution of their compositions.…”

“…Ni charge transfer and the Ni d-Si p hybridization effect. 9,10) It is considered that the occurrence of Ni-Si bonding with its strong covalent character substantially reduces the site exchange probability of these Ni and Si atoms in the L1 2 matrix. Thus, our interest in this study was focused on the influence of Si in the microstructure evolution related to the L1 2 !L1 2 +D0 22 phase separation of Ni 3 Al 1Àx V x alloys.…”

First-Principles Study of the Structural, Elastic, and Mechanical Properties of Ni3Ga Compound under Pressure

“…Intermetallic compounds Ni 3 Al, Ni 3 Ga, and Ni 3 Mn provide a class of systems exhibiting many interesting mechanical and electronic properties that make them attractive for structural applications at elevated temperatures [2].…”

“…First-principles total--energy electronic structure calculations based on the full-potential linear mun-tin-orbital method have been used to study the electronic and elastic properties of the Ni 3 X (X = Al, Ga, Mn) [2]. The electronic structures, mechanical and magnetic properties of Ni 3 Ga, Ni 3 Al, and * corresponding author; e-mail: boucetta_said02@yahoo.fr Ni 3 In have been studied by spin-density functional theory and also by X-ray absorption near-edge spectra [3,4].…”