Order–disorder transition of alloys

Abstract

Ab initio total-energy calculations, based on the exact muffin-tin orbitals method, are used to determine the equilibrium chemical configuration of alloy as a function of disorder and temperature. The transition from a substitutionally disordered face-centred-cubic crystallographic phase to an ordered phase is monitored using the coherent potential approximation which allows us to continuously scan the order parameter and thermodynamics of the alloy. We find signs of a first-order phase transition from a substitutionally disordered state to a partially ordered state around 210 K temperature and the completely ordered state is predicted around 90 K.

Keywords:

• Disordered systems
• crystal structure
• phase transitions
• preferential site ordering
• computer simulations
• metals and alloys

Acknowledgements

The computer resources of the Finnish IT Center for Science (CSC) and the FGI project (Finland) are acknowledged. L.V. acknowledges the Swedish Research Council, the Swedish Foundation for Strategic Research and the Hungarian Scientific Research Fund (OTKA 84078 and 109570).

Notes

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Swedish Research Council, the Swedish Foundation for Strategic Research and the Hungarian Scientific Research Fund [OTKA 84078 and 109570].