First-principles study of point defects in Ni3Al

• Published in: Philosophical magazine (Abingdon, England) Vol. 94; no. 1; pp. 20 - 34
• Main Authors: Ruban, Andrei V., Popov, V.A., Portnoi, V.K., Bogdanov, V.I.
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 02.01.2014
• Subjects: carbon interstitials; defect formation energies; Ni3Al; site preference; strain-induced interactions
• ISSN: 1478-6435; 1478-6443; 1478-6443
• DOI: 10.1080/14786435.2013.838647

The energetics and structural properties of native, substitutional and interstitial defects in Ni Al have been investigated by first-principles methods. In particular, we have determined the formation energies of composition conserving defects and established that the so-called penta defect, which consists of four vacancies on Ni sublattice and Ni antisite on the Al sublattice, is the main source of vacancies in Ni Al. We show that this is due to the strong Ni-site preference of vacancies in Ni Al. We have also calculated the site substitution behaviour of Cu, Pd, Pt, Si, Ti, Cr, V, Nb, Ta and Mo and their effect on the concentration expansion coefficient. We show the latter information can used for an indirect estimate of the site substitution behaviour of the alloying elements. The solution energy of carbon and its effect on the lattice constant of Ni Al have been obtained in the dilute limit in the first-principles calculations. We have also determined the chemical and strain-induced carbon-carbon interactions in the interstitial positions of Ni Al. These interactions have been subsequently used in the statistical thermodynamic simulations of carbon ordering in Ni Al.