It was recalled that recent success in growing sub-10nm rare-earth disilicide nanowires on Si(001) had stimulated interest in understanding point defects in these silicides. Disilicides with the AlB2 structure (C32, hP3) had the formula, RESi1.67, suggesting the existence of vacancies on Si sub-lattice sites. Vacancy concentrations were obtained here by simultaneously measuring their lattice parameters and bulk densities. The results revealed 11.1% vacancies in one mole of RESi2. This implied that, in a unit cell of 9 sites, one of the 6 sites occupied by Si atoms was vacant.

Vacancy Concentrations in Binary Rare-Earth Disilicides with the Aluminum Diboride Structure. C.X.Ji, M.Huang, J.H.Yang, Y.A.Chang, R.Ragan, Y.Chen, D.A.A.Ohlberg, R.S.Williams: Applied Physics A, 2004, 78[3], 287-9