Cubic Germanium monochalcogenides (π-GeS and π-GeSe): Emerging materials for optoelectronic and energy harvesting devices

•First ever optical, mechanical and anisotropic properties of cubic GeX (X = S, Se) are studied.•2D & 3D surface visualization suggest that both chalcogenides are elastically anisotropic.•Debye temperature (θD) of π-GeS and π-GeSe are 262.28 K and 264.46 K, respectively.•Germanium chalcogenides are promising candidate for optoelectronic, thermoelectric devices.