Element-dependent unique properties of Janus Cr2I3X3 (X = F, Cl, Br) monolayer: Insight from first-principles calculations

•Three aspects of Janus Cr2X3I3 (X = F, Cl and Br) monolayers and pure CrX3 monolayers have been compared and detailly analyzed using density functional theory (DFT).•The electronic structure of Janus Cr2X3I3 monolayers determined by the mainly Cr-I interactions and the out-of-plane dipole moments.•Due to the structural change, the critical strains for the FM-AFM transition of the Janus Cr2I3X3 are smaller than that of both CrI3 and CrX3.•The Young's Modulus Y and Shear Modulus G of the Janus Cr2I3X3 monolayers are bigger than that of CrI3 and CrX3 caused by the Cr-X bond lengths in the Cr2I3X3 systems depart from equilibrium.