NaNO3 monolayer: A stable graphenelike supersalt with strong four-phonon scattering and low lattice thermal conductivity insensitive to temperature

Since the discovery of graphene, numerous efforts have been made to seek new two-dimensional (2D) graphenelike materials with intriguing properties. Here,we report a stable graphenelike supersalt NaNO3 monolayer composed of superhalogen NO3. The 2D NaNO3 monolayer is found to possess an ultralow isotropic Young's modulus (2.983 N/m) and a low thermal conductivity (1.65 W/mK @300 K), which is much lower than that of 2D NaCl monolayer (3.72 W/mK @300 K). We attribute this behavior to the strong anharmonicity induced by the weak bonding between Na and NO3 cluster and the large atomic displacements of O in the NO3 cluster. A giant four-phonon scattering leads to a 60% reduction in lattice thermal conductivity at 300 K compared to that of three-phonon scattering. Furthermore, temperature-induced phonon hardening causes the lattice thermal conductivity to be nearly temperature independent in the studied temperature range (100-350 K), displaying significant difference from the atom-based 2D materials.

Automated summary

In this study, a stable graphene-like monolayer of a superhalogen compound NaNO3 composed of NO3 clusters was reported. This monolayer exhibits low Young's modulus and thermal conductivity, attributed to the weak bonding between Na and NO3 clusters and large atomic displacements of O in the NO3 cluster.