Mechanical and thermal transport properties of monolayer PbI2 via first-principles investigations

With the synthesis of single-layer lead iodide (PbI2) in the laboratory in recent years, it has been widely used due to its stable structure and suitable bandgap (2.5 eV). We carried out first-principles calculations and a theoretical analysis to investigate the mechanical properties, electronic structure, and thermal transport properties of monolayer PbI2. We computed the elastic constant C-11 = 14.69 N m(-1), layer modulus = 9.35 N m(-1), and Young's modulus E-2D = 13.63 N m(-1). Our results indicate that monolayer PbI2 is more flexible than other two-dimensional materials, and it has good ductility. The Poisson's ratio v of monolayer PbI2 is 0.27, which means that ionic forces play a major role in the interatomic bonding for PbI2 layered by van der Waals forces. We also did first-principles calculations for the lattice thermal transport properties of monolayer PbI2 through the ShengBTE code. The calculated thermal conductivity of monolayer PbI2 at 300 K is 0.66 W/m K, which agrees well with the experimental data of 0.68 W/m K. Furthermore, its thermal conductivity is much lower than that of other two-dimensional materials. We concluded that the acoustic modes of monolayer PbI2 make a major contribution to its thermal conductivity.