Abstract
The free energy of the concerted exchange mechanism for self-diffusion in silicon is estimated using the thermodynamic integration method and Monte Carlo (MC) simulations with an interatomic potential fitted to reproduce local-density-approximation calculations. Anharmonicity and relaxation are fully taken into account in the calculations, since the phase space is extensively explored by the MC simulations. The results indicate that the concerted exchange mechanism can have a significant contribution to the self-diffusion constant in silicon. \textcopyright{} 1996 The American Physical Society.
Highlights
Atomic diffusion in solids plays a very important role for various physical properties
Anharmonicity and relaxation are fully taken into account in the calculations, since the phase space is extensively explored by the MC simulations
The TI method allows for an efficient sampling of the phase space
Summary
Atomic diffusion in solids plays a very important role for various physical properties. Theoretical studies[1] found an activation enthalpy for defect mechanisms to be in the range 3.5– 4.5 eV, in reasonable agreement with experimental data, which lie between 4.1 and 5.1 eV.[2] Pandey has proposed a different mechanism, the concerted exchangeCE, in which, two neighboring atoms exchange positions along a specific path, without the intervention of a native defect.[3] The two atoms that are exchanging positions in the CE mechanism execute a complex motion in three-dimensional space in order to avoid large energy barriers. The calculated activation enthalpy of 4.3 eV for this mechanism[3] is similar to those of the defect mechanisms and lies in the range of the experimental data
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