Ordering of structural vacancies in non-stoichiometric Co3AlCx alloys was studied

using a combination of first-principles total-energy calculations, a cluster

expansion technique, and Monte Carlo simulations. In the proximity of the

experimentally observed composition of x~0.59, an exhaustive ground-state search

yielded two stable vacancy-ordered structures: a cubic Co3AlC0.5 phase and a

trigonal Co3AlC0.667 phase. By performing finite-temperature Monte Carlo

simulations, the order-disorder transition temperatures of Co3AlC0.5 and

Co3AlC0.667 were predicted to be ~1925 and ~1630K, respectively.

Vacancy Ordering in Co3AlCx Alloys: a First-Principles Study. C.Jiang: Physical

Review B, 2008, 78[6], 064206