Point Defect Energies in L12-Ordered Ni3Al
Experimental investigation of order-order relaxations in Ni3Al by residual resistometry yielded a very high ordering activation energy of about 4.6eV being in correspondence with tracer experiments, where the tracer atom substitutes the Al-atom. Qualitatively, this might be interpreted by breaking of bonds to the 12 surrounding Ni nearest neighbour atoms of the ordered Ll2-lattice. For the purpose of a more fundamental understanding the properties of vacancies and antisites in Ni3Al were studied by means of ab-initio calculations for supercells. Formation energies for Ni- and Al-vacancies were derived using a grandcanonical ensemble. Further, vacancy migration energies were determined successively displacing atoms from their equilibrium position to a vacant nearest neighbour position. Correlated jumps during a jump cycle were also taken into account.
Key wordsLl2-intermetallics point defects defect energies ab-initio calculations
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