First-principles calculation of phase stability and cohesive properties of Ni-Sn intermetallics

Gautam Ghosh*

*Corresponding author for this work

Research output: Contribution to journalArticle

35 Scopus citations

Abstract

The cohesive properties of Ni-Sn intermetallics (stable, metastable, and virtual), hitherto unexplored by density-functional theory (DFT) methods, are reported. Specifically, the total energies and cohesive properties of Ni, Sn, and 27 Ni-Sn intermetallics are calculated from first-principles, using ultrasoft pseudopotentials (USPP) and both local-density approximation (LDA) and generalized-gradient approximation (GGA) for the exchange-correlation functional. Among the intermetallics considered, the ground-state structures are consistent with experimental observations; however, not all of them are registered in the equilibrium-phase diagram. An important result of this systematic study, using both USPP-LDA and USPP-GGA, is that oC 20-NiSn4 is predicted to be the ground-state structure. Only recently, this phase has been observed as a product of the interfacial reaction in Ni/Sn diffusion couples. In addition, we find that the thermodynamic stability of a tetragonal phase, tP 10-NiSn4, is very similar to that of oC 20-NiSn4. The elastic stability of both tP 10-NiSn4 and oC 20-NiSn4 is confirmed by calculating their single-crystal elastic constants. The calorimetric data for the enthalpy of formation of stable intermetallics show an agreement that is better for those calculated with USPP-LDA than those calculated with USPP-GGA. In general, the experimental lattice parameters of stable and metastable phases are found to lie between those calculated using USPP-LDA and those calculated using USPP-GGA; however, in several cases, the values calculated using USPP-GGA agree to within 1 pct of the experimental data. The Ni3Sn2(ht) ⇌ Ni3 Sn2(lt) transformation is discussed in terms of supergroup-subgroup relations. The bonding between the Ni and the Sn is discussed based on the analyses of the density of states (DOS) and the charge densities.

Original languageEnglish (US)
Pages (from-to)4-23
Number of pages20
JournalMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Volume40
Issue number1
DOIs
StatePublished - Jan 1 2009

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Metals and Alloys

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