Role of configurational entropy in the thermodynamics of clusters of point defects in crystalline solids

Received 28 March 2005; revised manuscript received 24 May 2005; published 20 July 2005The internal configurational entropy of point defect clusters in crystalline silicon is studied in detail byanalyzing their potential energy landscapes. Both on-lattice and off-lattice calculation approaches are employedto demonstrate the importance of off-lattice configurational states that arise due to a large number of inherentstructures local minima in the energy landscape generated by the interatomic potential function. The resultingcluster configurational entropy of formation is shown to exhibit behavior that is qualitatively similar to thatobserved in supercooled liquids and amorphous solids and substantially alters the thermodynamic properties ofpoint defect clusters in crystals at high temperature. This behavior is shown to be independent of interatomicpotential and cluster type, and suggests that defects in crystals at high temperature should be generally de-scribed by a quasicontinuous collection of nondegenerate states rather than as a single ground state structure.The modified thermodynamic properties of vacancy clusters at high temperature are found to explain a long-standing discrepancy between simulation predictions and experimental measurements of vacancy aggregationdynamics in silicon.DOI: 10.1103/PhysRevB.72.014119 PACS number s : 61.72.Bb, 61.72.Qq

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