Defect formation energies of Ag- and Sr-doped 3C-SiC: A first-principles study

In this study, we conduct calculations of Ag- and Sr-doped in 3C-SiC using density-functional. To model defective systems, we dope Ag and Sr atoms in substitutional and interstitial sites. We use a supercell model consisting of 64 atoms and relax all atoms so that the atomic forces are less than
5
.
0
×
1
0
−
3
eV/Å. Then, we calculate the defect formation energies for each system. The calculated defect formation energies are 5.67eV and 7.77eV for substitutional Ag and Sr, respectively. In the case of the interstitial sites, the lowest defect formation energies are 10.36eV (Ag) and 14.63eV (Sr). We conclude that Ag and Sr are energetically favorable to be trapped at the substitutional site. Furthermore, the substitutional configuration of Ag is more stable than that of Sr. We check the converged value of the defect formation energies using a 216-site supercell and find that the energy difference is only 0.21eV. Thus, the 64-atom supercell is reliable for the calculations.