Investigation of Point Defect Clusters in Silicon Using Parallel Molecular Dynamics

AuthorsFriedrich von Gottberg, Robert A. Brown, Talid Sinno
Publication Date:
October 16, 1996
Journal
Journal of Computer-Aided Materials Design

Citation: T. Sinno, F. K. von Gottberg, R. A. BrownInvestigation of Point Defect Clusters in Silicon Using Parallel Molecular Dynamics, Journal of Computer-Aided Materials Design, 4 (1997) 29.

Abstract: A parallel molecular dynamics algorithm is presented for computingconfigurations of relatively large defects in crystalline silicon, as modelledby the Stillinger–Weber (SW) three-body interatomic potential. Thealgorithm is based on a partitioning of physical space among the N processorswith atoms migrating freely between the partitions. Implementation on aneight-processor IBM SP2 computer shows the increased efficiency withsimulation size expected because of the increased computational load perprocessor relative to communication overhead. The parallel efficiency reached 70% for 21 952 atoms. Calculations are presented for the thermodynamics offormation of interstitial and vacancy clusters containing up to seven pointdefects. The clusters were relaxed within a host lattice of about 3000 siliconatoms subjected to periodic boundary conditions. Free energies of formationfor temperatures 500 K ≤ T ≤ 1600 K were computed using thermodynamicintegration. Computed equilibrium distributions for these clusters show ashift to the larger species at lower temperatures, as expected. The SWpotential predicts greater driving forces for interstitial aggregation thanvacancy aggregation across the entire temperature range. Model calculationsfor a large vacancy cluster are also presented to demonstrate the utility ofthe algorithm for exploring very large defects in silicon.