Dec 5, 2024
2:00pm - 2:15pm
Hynes, Level 2, Room 208
Bikash Timalsina1,Keivan Esfarjani1,Huy Nguyen1
University of Virginia1
The lattice distortion in a crystal has a significant effect on thermal transport properties. Such an effect is very prominent in entropy-stabilized oxides. Herein, using neuroevolution machine learning potential and molecular dynamics simulation we demonstrate that the lattice thermal conductivity of J14(MgCoNiCuZnO<sub>5</sub>) decreases from 2.60±0.2 Wm<sup>-1</sup>K<sup>-1</sup> at 300 K to 2.07±0.05 Wm<sup>-1</sup>K<sup>-1</sup> at 900 K, consistent with the experimental findings. The results show that the reduction in lattice thermal conductivity as a function of temperature in J14 is due to a decreased phonon mean free path. Next, the composition of zinc and nickel in J14 is varied by 30% to investigate the effect of stoichiometric change on the lattice thermal conductivity at room temperature. While more Zn causes more distortions, an addition of Ni reduces distortions. Therefore, one expects related changes in the thermal conductivity. The results indicate that the composition with more zinc in J14 (Mg <sub>0.2</sub>Co<sub>0.2</sub>Ni<sub>0.14</sub>Cu<sub>0.2</sub>Zn<sub>0.26</sub>O) and more nickel in J14 (Mg<sub>0.2</sub>Co<sub>0.2</sub>Ni<sub>0.26</sub>Cu<sub>0.2</sub>Zn<sub>0.14</sub>O) have been thermodynamically stable within our simulation time. The lattice thermal conductivity with more zinc in J14 is 2.54±0.2 Wm<sup>-1</sup>K<sup>-1</sup> and with more nickel in J14 is 2.77±0.2 Wm<sup>-1</sup>K<sup>-1</sup> at room temperature. We find therefore that there is indeed correlation between the amount of distortions and the thermal conductivity in these compounds. These findings are supported by the fact that adding more zinc to J14 leads to a decrease in the phonon mean free paths, while adding more nickel to J14 leads to an increase in the phonon mean free paths at room temperature. The neuroevolution machine learning interatomic potential is beneficial to studying and tuning thermal transport properties such as lattice thermal conductivity for entropy-stabilized oxides.