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First principles investigation of thermal conductivity in Magnesium Selenide(MgSe) with different crystalline phase

Magnesium Selenide (MgSe) is a wide bandgap semiconductor with applications in optoelectronics and energy conversion technologies. Understanding thermal conductivity (k) of MgSe is critical for optimum design of thermal transport in these applications. In this work, we report the temperature and length dependence lattice thermal conductivity of magnesium selenide (MgSe) with different crystallographic phases; zincblende, rocksalt, wurtzite and nickel arsenic, using first principles computations. Computations reveal significant differences in thermal conductivity (k) of MgSe for different phases. The observed trend in thermal conductivities is : kNiAs < krocksalt < kwurtzite < kzincblende. Our first principles calculations show a room temperature low k of 4.5 Wm-1K-1 for the NiAs phase and a high k of 20.4 W/mK for wurtzite phase. These differences are explained in terms of a phonon band gap in the vibrational spectra of zincblende and wurtzite phases, which suppresses scattering of acoustic phonons, leading to high phonon lifetimes.