Thermal conductivity study of 2D Si₄C₈ materials by anharmonic phonon renormalization

In this investigation, we employed the anharmonic phonon renormalization method to analyze the thermal conductivity of two-dimensional (2D) carbon materials, while also examining the influence of quartic (fourth-order) scattering on heat transport within this class of materials. Our study centered on a representative silicon-carbon (Si-C) 2D system, Si₄C₈. Notably, conventional Boltzmann transport equation (BTE) calculations with harmonic phonons are inadequate for estimating the thermal conductivity of these materials due to the emergence of imaginary frequencies. Consequently, to elucidate the primary contributors to its heat transport, we employed an integrated yet novel computational framework rooted in a first-principles methodology. This approach combines self-consistent phonon (SCP) theory and the BTE to scrutinize the thermal conduction behavior; the BTE is resolved in conjunction with SCP theory to comprehensively address the quartic anharmonic effects, encompassing both four-phonon (4ph) scatterings and the temperature-induced shift of phonon frequencies. Based on the calculation results, it is evident that the meticulous incorporation of anharmonicity renormalization is pivotal for precise evaluation of the thermal conductivity of 2D Si₄C₈ and establishing coherent temperature dependency. Through this comprehensive examination, we aim to establish a systematic methodology for investigating the thermal transport mechanisms of 2D Si-C phases with similar bonding networks, offering insights into the intricate relationships between their structural, mechanical, electronic, and thermal properties.