Understanding intrinsic phonon thermal transport in two-dimensional γ-GeX (X = S, Se, Te) from first principles

•The intrinsic phonon thermal conductivities of γ-GeX (X = S, Se, Te) are relative low due to the low phonon velocity and large phonon scattering rates.•Small relative atomic mass difference and asymmetric distribution structure of electron localization are beneficial to obtain low phonon thermal conductivity of γ-GeS.•This work provides new characteristics for future research on thermal applications of hexagonal two-dimensional IV-VI materials.