Theoretical investigation of the stability of crystalline silicon dicarbide

Abstract

While Si, C and SiC are very well known materials that have been extensively studied in their multitude of structures and allotropes, there is, surprisingly, a dearth of reliable information for off-50:50 compounds involving Si and C. Do such compounds exist and, if so, what are the plausible structures for these compounds? Using first principles total energy methods, we generally explore these questions before investigating in some detail the structures involving silicon dicarbide. Of the structures considered, our results show that the tetragonal glitter phase is lowest in energy. Of the two higher energy cubic structures that we considered, we note that there is a continuous transition from the high energy fluorite structure to the lower energy pyrite structure. We predict the transition pressure from glitter to pyrite to be 24.7 GPa. We give detailed structural and electronic properties for these systems. Since diamond and SiC are known for their hardness properties, we compute the elastic properties of SiC2, and we make an assessment of its hardness properties. We propose the glitter structure to be a plausible phase for SiC2.