Mechanical and electronic properties of C-Si alloys in the P2221 structure

The structural, mechanical, elastic anisotropy and electronic properties of C-Si alloys in the orthorhombic structure (Space group: P2221) are investigated using first-principles calculations based on density functional theory (DFT) with the plane wave basis set as implemented in the CASTEP code. The lattice parameters, elastic constants and elastic modulus are in excellent agreement with the other theoretical data. The elastic anisotropy is characterized by calculating several different anisotropic indexes and the anisotropic properties of the sound velocities along diverse directions. From our calculations, the calculated elastic constants for the P2221 C10, Si10 and C-Si alloys indicate that they are mechanically stable, the B/G values and Poisson's ratio v show that the C-Si alloys are brittle, and the shear modulus, Young's modulus and the anisotropy factor calculations show that the C-Si alloys have elastic anisotropy. Finally, the analysis on the electronic structures shows that the C-Si alloys are indirect band gap semiconductors.