6608963Recent advances in computational materials science present novel opportunities for structure discovery and optimization, including uncovering of unsuspected compounds and metastable structures, electronic structure, surface and nano-particle properties. The practical realization of these opportunities requires systematic generation and classification of the relevant computational data by high-throughput methods. In this paper we present Aflow (Automatic Flow), a software framework for high-throughput calculation of crystal structure properties of alloys, intermetallics and inorganic compounds. The Aflow software is available for the scientific community on the website of the materials research consortium, aflowlib.org. Its geometric and electronic structure analysis and manipulation tools are additionally available for online operation at the same website. The combination of automatic methods and user online interfaces provide a powerful tool for efficient quantum computational materials discovery and characterization.

No abstract

No abstract

First, second and third nearest neighbor pair mixing potentials for equiatomic FePt alloys were calculated from first principles by the Connolly-Williams method within the canonical cluster expansion formalism. It was demonstrated that the Connolly-Williams potentials (based on completely ordered states) and the Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) potentials (based on completely disordered state) can be brought into very close correspondence to each other simply by increasing the magnitude of the strain-induced interactions added to the KKR-CPA potential. Using the mixing potentials obtained in this manner, the dependency of equilibrium L10 ordering on temperature was studied for bulk and for (approximately) spherical nanoparticles ranging in size from 2.5 to 6nm. The order parameter was calculated using Monte Carlo simulation and the analytical ring approximation. The calculated order-disorder temperature for bulk (1495-1514 K) was in relatively good agreement (4% error) with the experimental value (1572K). For nanoparticles of finite size, the (long range) order parameter changed continuously from unity to zero with increasing temperature. Rather than a discontinuity indicative of a phase transition, we obtained an inflection point in the order as a function of temperature. This inflection point occurred at a temperature below the bulk phase transition temperature and decreased as the particle size decreased. Our calculations predict that 3.5nm diameter particles in configurational equilibrium at 600• C (a typical annealing temperature for promoting L10 ordering) have an L10 order parameter of approximately 0.84 (compared to a maximum possible value equal to unity). According to our investigations, the experimental absence of (relatively) high L10 order in 3.5nm diameter nanoparticles annealed at 600• C or below is primarily a problem of kinetics rather than equilibrium.