Atomistic origin of the thermodynamic activation energy for self-diffusion and order-order relaxation in intermetallic compounds I: analytical approach

Abstract

The general state of knowledge of diffusion and order-order relaxation in a long-range ordered system is summarised. A consistent atomistic description of self-diffusion and the order-order relaxation process is discussed in terms of effective atomic jump frequencies and the current degree of chemical long-range order. It is demonstrated that the thermodynamic activation energies of self-diffusion and the order-order relaxation can be expressed in terms of the activation energies of more elementary processes. The derived expressions differ from each other indicating that although both processes are controlled by the same vacancy-mediated elementary atomic jumps, the values of their thermodynamic activation energies can be different.

Keywords:

• Self-diffusion
• relaxation
• intermetallics

Acknowledgement

Access to the computation facilities at the ACK Cyfronet AGH, Krakow (supercomputer Prometheus) is greatly appreciated.