Research paper published

Summary

In this paper, we systematically investigate phonon thermal transport in indium iodides that adopt either layered (InI) or molecular-crystal-like (InI₃) structures, using first-principles anharmonic lattice dynamics. By comparing particle-like transport (Peierls–Boltzmann contribution) and wave-like transport (interband-tunneling-related contribution), we show that the lattice thermal conductivities of both materials remain below 1 W m^-1 K^-1 over a broad temperature range. We further clarify that the wave-like contribution becomes comparable to the particle-like contribution in InI₃, whereas it remains negligible in InI. We also examine the experimentally reported high-pressure phase of InI₃. Motivated by indications of stacking faults and partial disorder in indium-site occupancy, we construct several ordered structural models with different stacking sequences and evaluate their energetics and thermal transport properties. The results indicate that the energetic preference among stacking sequences is small and the lattice thermal conductivities are similar across models, suggesting that in-plane thermal transport is governed primarily by the vibrational properties of the In₂I₆ layers themselves rather than by the specific stacking sequence. This work is a result of a collaboration with the research group led by Associate Professor Mizuguchi at Tokyo Metropolitan University and the Advanced Thermal Analysis Research Group, Research Institute for Material Measurement, National Institute of Advanced Industrial Science and Technology (AIST).