Insights into lanthanide contraction effects in intermetallic LnAuSb (Ln = La, Ce, Pr) compounds

Abstract The structural, elastic, and dynamical properties of LnAuSb (Ln = La, Ce, Pr) are systematically investigated using first-principles calculations. The physical properties of LnAuSb compounds were affected by the substitution of different lanthanide elements. We observed a decrease in lattice parameters from La to Pr. This is consistent with the general trend of decreasing ionic radii throughout the lanthanide series. These changes can be attributed to lanthanide contraction behaviour. The resulting structural contraction is accompanied by a slight increase in elastic constants and phonon frequencies, indicating that the lattice is becoming stiffer and interatomic interactions are stronger. The calculated formation energies, elastic constants, and phonon dispersion curves confirm the thermodynamically, mechanical, and dynamical stability of all compounds. The estimated minimum thermal conductivity values of these compounds are low. Moreover, we observed a decrease in lattice thermal conductivity as the temperature increased. These results suggest that LnAuSb compounds (Ln = La, Ce or Pr) are promising materials for high-temperature applications, such as thermal barrier coatings and refractory systems, thanks to their directional mechanical properties and low thermal conductivity at high temperatures.