Thermal and mechanical properties of deep-ultraviolet light sources candidate materials <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>BeGeN</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math> by machine-learning molecular dy

It is well known that thermal and mechanical properties are the key physical parameters of deep-ultraviolet (DUV) light sources materials, and play critical roles in practical applications. In this work, the thermal conductivity, thermal expansion coefficient, and mechanical performance of newly predicted DUV materials are systematically investigated by means of neuroevolution potential (NEP) combined molecular dynamics (MD) simulation. Both equilibrium molecular dynamics (EMD) and homogeneous nonequilibrium molecular dynamics (HNEMD) calculations demonstrate that the ${\mathrm{BeGeN}}_{2}$ hosts the best thermal transport performance with $39.4\phantom{\rule{0.16em}{0ex}}{\mathrm{Wm}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ at room temperature, among the five DUV light-emitting candidates (i.e., ${\mathrm{BeGeN}}_{2}, {\mathrm{Mg}}_{3}{\mathrm{NF}}_{3},\phantom{\rule{0.16em}{0ex}}{\mathrm{KCaBr}}_{3}$, KHS, and RbHS). Significant boosted thermal conductivity (about 104 ${\mathrm{Wm}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$) could be further observed in compressive ${\mathrm{BeGeN}}_{2}$ with $3%$ strain, implying the ability of ${\mathrm{BeGeN}}_{2}$ to address the severe heat dissipation issue in DUV optoelectronic devices. By performing phonon spectral energy density analysis, we reveal that such enhancement of thermal conductivity mainly originates from the increased phonon lifetime in the low-frequency region. Meanwhile, our calculations also show that the coefficient of thermal expansion of ${\mathrm{BeGeN}}_{2}$ is merely $25.87\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}/\mathrm{K}$, the corresponding Pugh modulus ratio (G/B), and the Vickers hardness are, respectively, 0.719 and 22.239 GPa. The findings presented in this work authenticate that the ${\mathrm{BeGeN}}_{2}$ possesses a high thermal conductivity and stable mechanical properties, foreshowing the great potential in DUV light-emitting field applications.