We use the self-consistent linear-muffin-tin-orbital method in the atomic-sphere approximation for the calculation of the electronic structure, total energies, and hyperfine fields for isolated Al point defects and for trigonal Al defect pairs in silicon. Many-body effects are treated in the local-density approximation of density-functional theory and the band gap appropriate for Si is obtained using the scissors-operator technique. We find that the substitutional AlSi point defect is thermodynamically stable while the (AlSi-AlSi) pairs, the interstitial Ali point defects, the (Ali-AlSi) pairs, and the (Ali-Ali) pairs are metastable. We calculate the hyperfine-interaction (HFI) matrix elements, the contact term, as well as the full dipolar tensor for the Al nuclei and for the first ligand shells. We discuss results obtained for several trigonal (Ali-AlSi) pairs which differ with respect to the distance between the two Al atoms. No pair was found that has the large hyperfine-interaction matrix element with the AlSi nucleus, which is the characteristic of Si-G20. We have, therefore, calculated different clusters where in addition to the trigonal (Ali-AlSi) pair another AlSi or CSi constituent was built-in, thus preserving the trigonal symmetry. The search was unsuccessful, however.
ASJC Scopus subject areas
- Condensed Matter Physics