First principles investigation on the structural, mechanical and electronic properties of OsC2

The structural, mechanical and electronic properties Of OsC2 were investigated by use of the density functional theory. Seven structures were considered, i.e., orthorhombic Cmca (No. 12, OsSi2), Pmmn (No. 59, 002) and Pnnm (No. 58, OsN2); tetragonal P4(2)/mnm (No. 136, OsO2) and 14/mmm (No. 139, CaC2); cubic Fm-3m (No. 225, CaF2) and Pa-3 (No. 205, PtN2). The results indicate that Cmca in OsSi2 type structure is energetically the most stable phase among the considered structures. It is also stable mechanically. OsC2 in Pmmn phase has the largest bulk modulus 319 GPa and shear modulus 194 GPa. The elastic anisotropy is discussed. (C) 2009 Elsevier B.V. All rights reserved.