A compound unit method for incorporating ordered compounds into lattice models of alloys

• Published in: Computational materials science 2016-06, Vol.118, p.172-179
• Main Authors: Kalidindi, Arvind R., Schuh, Christopher A.
• Format: Article
• Language: English
• Subjects: Alloy; Alloys; Calibration; Computational efficiency; Energy of formation; Formations; Intermetallic; Ising model; Lattices; Mathematical models; Monte Carlo; Ordered compound; Pairwise; Precipitates
• ISSN: 0927-0256; 1879-0801
• DOI: 10.1016/j.commatsci.2016.02.039

[Display omitted] •A method for incorporating known ordered compounds into a lattice model is proposed.•The method maintains the simplicity and broad applicability of the pairwise model.•A compound unit is used to capture the compound’s structure and formation energy.•Monte Carlo simulations show that this method produces proper two-phase behavior. Lattice models can be a basic tool for alloy design, due to their ability to capture the most important thermodynamic and kinetic phenomena of a wide-range of alloys at a low computational cost. However, in order to correctly treat ordered precipitates at off-stoichiometric compositions requires multi-body potentials, and these can be challenging to calibrate to known alloy behaviors. Here we introduce a simple means of capturing the multi-body terms needed to treat ordered compounds in a lattice model based on defining “compound units”. This approach is particularly designed for, and easily calibrated in, cases where the structure and formation energy of equilibrium compounds are already known. This is accomplished by defining a compound unit that derives its energy from the formation energy of the compound as an a priori input. The method is illustrated for a binary alloy with D03 and B2 stable compounds.