Electronic structure calculations are done at density-functional theory (DFT) level 97 using the all-electron, full-potential density-theory package FHI-aims. The exchangecorrelation interactions were treated using the Perdew-Burke-Enzerhof (PBE) functional 101 together with the many-body dispersion (MBD) method 102 to account for long-range van der Waals interactions. For comparison, we also used the hybrid PBE0 functional. The FHI-aims-specific tier 2 basis set and tight settings have been used. The convergence criterion for the total energy was set to 10 -5 eV.