Rocksalt or cesium chloride? Investigating the relative stability of the cesium halide structures with Random Phase Approximation based methods*

The Random Phase Approximation (RPA) is gaining immense popularity as the benchmark of semilocal methods such as LDAs and GGAs, as it naturally incorporates weak interaction and eliminates self-interaction error in its exchange component. By taking cesium halides as benchmarks for ionic solids, we present the comparative assessment of RPA based methods with the newly developed SCAN meta-GGA, which incorporates the intermediate-range of dispersion [1]. We also assess various long-range dispersion corrections to SCAN such as SCAN+D3 and SCAN+rVV10. We have demonstrated that RPA is quite successful in describing the ground state properties of these alkali halides, especially smaller fluorides and chlorides. Beyond RPA methods such as rALDA with an exchange-correlation kernel systematically improve upon RPA results for larger bromides and iodides. Though rALDA and rAPBE share a common formalism, rAPBE fails to predict the equilibrium properties of these halides. We have also demonstrated that the SCAN and dispersion-corrected SCAN can also accurately describe the equilibrium properties of these halides and can be good alternatives where computational power can be saved.

[1] Niraj K Nepal, Jefferson E. Bates, Adrienn Ruzsinszky, to be submitted.