Role of silicon vacancies in yttrium-disilicide compounds from ab initio calculations

Abstract

The structural properties of the compound ${\mathrm{YSi}}_2$ are investigated by means of ab initio simulations based on density-functional theory. More particularly we emphasize the role played by Si vacancies, show that the ${\mathrm{Th}}_3$ ${\mathrm{Pd}}_5$ structure can be deduced from the ${\mathrm{AlB}}_2$ structure by a relaxation process around the Si vacancies within the (0001) plane. A specific ordered arrangement of the Si vacancies along the [0001] direction is found to be energetically the most favorable. Geometries obtained from our theoretical calculations are in good agreement with experimental results.