Combined ab initio/CALPHAD modeling of fcc-based phase-equilibria in the Ir-Nb system

Taichi Abe, Ying Chen, Yoko Yamabe-Mitarai, Hiroshi Numakura

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


A preliminary thermodynamic assessment of the Ir-Nb system, one of the key binary systems of the Ir-based refractory superalloys, has been performed by combining ab initio calculations and the CALPHAD (CALculation of PHAse Diagrams) technique. The ground-state formation enthalpies have been calculated by the full-potential linearized augmented plane wave method. The free energies at finite temperatures have been estimated using the cluster variation method, where the effective cluster interaction energies have been extracted from the formation enthalpies by the cluster expansion method. The liquid and A1 phases are modeled as substitutional solutions. The L10 and L12 phases are described using the four-sublattice model with the formula (Ir,Nb)1/4(Ir,Nb)1/4(Ir,Nb)1/4(Ir,Nb)1/4, while other solid phases are not considered in the present assessment. The obtained parameter set reproduces well the characteristic features of the experimental phase diagram and thermodynamic quantities.

Original languageEnglish
Pages (from-to)353-360
Number of pages8
JournalCalphad: Computer Coupling of Phase Diagrams and Thermochemistry
Issue number2
Publication statusPublished - 2008 Jun
Externally publishedYes


  • Ab initio calculations
  • Cluster variation method
  • Compound energy formalism
  • Refractory superalloy
  • Short range ordering

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Computer Science Applications


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