Electronic, thermodynamic, and effect of pressure on mechanical properties in CoTiSb and CoTiBi semi-Heuslers

Abstract

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 (