Dissimilar thermal transport properties in $κ$-Ga$_2$O$_3$ and $β$-Ga$_2$O$_3$ revealed by machine-learning homogeneous nonequilibrium molecular dynamics simulations

The lattice thermal conductivity (LTC) of Ga $_{2}$ O $_{3}$ is an important property due to the challenge in the thermal management of high-power devices. We develop machine-learned neuroevolution potentials for single-crystalline $β$ -Ga $_{2}$ O $_{3}$ and $κ$ -Ga $_{2}$ O $_{3}$ , and apply them to perform homogeneous nonequilibrium molecular dynamics simulations to predict their LTCs. The LTC of $β$ -Ga $_{2}$ O $_{3}$ was determined to be 10.3 $\pm$ 0.2 W/(m K), 19.9 $\pm$ 0.2 W/(m K), and 12.6 $\pm$ 0.2 W/(m K) along [100], [010], and [001], respectively, aligning with previous experimental measurements. For the first time, we predict the LTC of $κ$ -Ga $_{2}$ O $_{3}$ along [100], [010], and [001] to be 4.5 $\pm$ 0.0 W/(m K), 3.9 $\pm$ 0.0 W/(m K), and 4.0 $\pm$ 0.1 W/(m K), respectively, showing a nearly isotropic thermal transport property. The reduced LTC of $κ$ -Ga $_{2}$ O $_{3}$ versus $β$ -Ga $_{2}$ O $_{3}$ stems from its restricted low-frequency phonons up to 5 THz. Furthermore, we find that the $β$ phase exhibits a typical temperature dependence slightly stronger than $\sim T^{- 1}$ , whereas the $κ$ phase shows a weaker temperature dependence, ranging from $\sim T^{- 0.5}$ to $\sim T^{- 0.7}$ .

Dissimilar thermal transport properties in $κ$ -Ga $_{2}$ O $_{3}$ and $β$ -Ga $_{2}$ O $_{3}$ revealed by machine-learning homogeneous nonequilibrium molecular dynamics simulations

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Dissimilar thermal transport properties in $κ$ -Ga $_{2}$ O $_{3}$ and $β$ -Ga $_{2}$ O $_{3}$ revealed by machine-learning homogeneous nonequilibrium molecular dynamics simulations

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Dissimilar thermal transport properties in κκ-Ga22​O33​ and ββ-Ga22​O33​ revealed by machine-learning homogeneous nonequilibrium molecular dynamics simulations

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Dissimilar thermal transport properties in κκ-Ga22​O33​ and ββ-Ga22​O33​ revealed by machine-learning homogeneous nonequilibrium molecular dynamics simulations

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Dissimilar thermal transport properties in $κ$ -Ga $_{2}$ O $_{3}$ and $β$ -Ga $_{2}$ O $_{3}$ revealed by machine-learning homogeneous nonequilibrium molecular dynamics simulations

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Dissimilar thermal transport properties in $κ$ -Ga $_{2}$ O $_{3}$ and $β$ -Ga $_{2}$ O $_{3}$ revealed by machine-learning homogeneous nonequilibrium molecular dynamics simulations

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