A study was made of intrinsic point defects in magnesium silicide, Mg2Si, by using

density-functional theory. Evaluating the formation energies of point defects, it was

shown that the n-type electric conductivity of Mg2Si originated from the formation

of positively charged Mg ions at interstitial sites, regardless of the chemical

composition. The Born effective charge tensors and the valence charge density

distribution were calculated. They showed that Mg2Si was an ionic crystal

composed of Mg2+ and Si4− which had very different ionic radii: 0.6 and 2.1Å,

respectively. It was concluded that the unfavourable antisite defect, MgSi, was due

to the dissimilar ionic radii.

First-Principles Studies of Intrinsic Point Defects in Magnesium Silicide. A.Kato,

T.Yagi, N.Fukusako: Journal of Physics - Condensed Matter, 2009, 21[20], 205801