First-principles calculations of the self-interstitial cluster I-4 in Si

The I-4 cluster model, which is recently proposed as primarily self-interst itial clustering in Si [N. Arai et al., Phys. Rev. Lett. 78, 4265 (1997)], has been examined using the ab initio pseudopotential method based on the l ocal density-functional theory. All the bonds are well reconstructed with e nough bond charge and relatively small bond distortions. The formation ener gy per self-interstitial is 1.5 eV. This value is less than one half of tha t of isolated self-interstitials, although this is fairly larger than that of extended self-interstitial agglomerates such as {113} planar defects. Th e I-4 cluster has no electronic states inside the minimum band gap, which i s consistent with no previous experimental identification. The present resu lts quantitatively support the possible existence of the I-4 clusters as pr imary clusters or embryos of extended agglomerates. [S0163-1829(99)00535-4] .