A study of the thermodynamics of segregation and partial order at (111) antiphase boundaries in Ni₃Al

Abstract

The thermodynamic properties of thermal and athermal (111) antiphase-boundaries in Ni₃Al are computed from first principles. The effects of off-stoichiometry, partial disordering and segregation are evaluated and a rough estimate of the vibrational contribution to the antiphase-boundary energy is given. Although the vibrational effect is found to be small, the configurational effects are large, so that at non-zero temperature and in off-stoichiometric Ni₃Al the antiphase-boundary energy may be reduced to only half of that in perfectly ordered stoichiometric Ni₃Al at zero temperature. This suggests a discrepancy between electronic structure calculations and experimental measurements.