| Abstrakt: |
First principles technique based on density functional theory (DFT) is employed to study the structural, phonon, electronic, thermodynamic, and mechanical properties of CoTiSb and CoTiBi semi-Heuslers. The optimized structural parameters including lattice constant, bulk modulus, and formation energy were determined in three structural phase. The results obtained were found to be in agreement with available experimental and other theoretical results. CoTiSb and CoTiBi were found to be brittle, mechanically, dynamically, and thermodynamically stable, and exhibit an indirect band gap semiconductor property as revealed by the bandstructure, total and projected density of states. The effect of pressure on the elastic, and mechanical behaviors were investigated in a range of 0 - 30 GPa. Thermodynamic properties of CoTiSb and CoTiBi were calculated from 0 - 800 K. At room temperature, the Debye heat capacity (Cv) was found to be 68.6 and 70.43 J/K/mol for CoTiSb and CoTiBi. At low temperature, Cv, obeys the Debye power-law (Cv ∝ T³), and at eleviated temperature, Cv, agrees with the Dulong-Pitit law, and converged at a value of 73.94 and 74.22 J/K/mol for CoTiSb and CoTiBi, respectively. For the first time results have been obtained for CoTiBi semi-Heusler. These results may serve as reference to further studies. [ABSTRACT FROM AUTHOR] |
