**Density functional theory calculations of helium clustering in mono-,
di-, and hexa-vacancy in silicon**

L Pizzagalli and ML David and J Deres, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 214, 1700263 (2017).

DOI: 10.1002/pssa.201700263

Combining classical molecular dynamics and first-principles DFT
calculations, we perfom an extensive investigation of low energy
configurations for Hen Vm complexes in silicon. The optimal helium
fillings are hence determined for V-1, V-2, and V-6 ( figure on the
right), and the structures formed by helium atoms arrangements in the
vacancy defect are analyzed. For V-1 and V-2, the He atoms structure is
mainly controled by the host silicon matrix, whereas a high density
helium packing is obtained for V-6. For the latter, we estimate a helium
density of about 170 He nm(-3) in the center of the hexa-vacancy at the
optimal helium filling. **GRAPHICS** Relaxed structures obtained from DFT
calculations for configurations with the lowest formation energies: ( a)
He14V1, (b) He20V2, and ( c) He40V6. (C) 2017 WILEY-VCH Verlag GmbH &
Co. KGaA, Weinheim

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