Can Corrugated Si-Planes of CaSi2 Flatten under High Pressure?

Abstract

Stability and structural transformation under high pressure are investigated for polymorphs of calcium di-silicide (CaSi2) theoretically. Using LDA calculation we can show that sp2-bonded structures are stabilized at high pressure against popular trigonal structure with sp3-bonded corrugated Si-planes. Our result suggests that even A1B2 structure with flat honeycomb Si-planes, which has not been found for CaSi2 experimentally, could be obtained under high pressure at low temperature. Characteristics of structural transformation of CaSi2 is discussed in comparison with the graphite-diamond transformation in which sp3 bonding is selected at high pressure. [CaSi2, structural transformation, LDA calculation, layered material, high pressure synthesis]. © 1998, The Japan Society of High Pressure Science and Technology. All rights reserved.