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

Combining classical molecular dynamics and first‐principles DFT calculations, we perfom an extensive investigation of low energy configurations for HenVm complexes in silicon. The optimal helium fillings are hence determined for V1, V2, and V6 (figure on the right), and the structures formed by helium atoms arrangements in the vacancy defect are analyzed. For V1 and V2, the He atoms structure is mainly controled by the host silicon matrix, whereas a high density helium packing is obtained for V6. 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. Relaxed structures obtained from DFT calculations for configurations with the lowest formation energies: (a) He14V1, (b) He20V2, and (c) He40V6.