Direct determination of self-consistent total energies and charge densities of solids: A study of the cohesive properties of the alkali halides

PyADF — A scripting framework for multiscale quantum chemistry

“…This new molecule object is then used to initialize and run an adfsinglepointjob, for which a higher integration accuracy and a larger basis set are used (lines [19][20][21][22]. The new results object is then used to initialize and run an adfnmrjob (lines [24][25][26]. Finally, the get_all_shieldings method of the NMR job's results object is used to extract the calculated shieldings, which can then be printed (lines [28][29][30][31].…”

“…22,43 and 44 for details). By iteratively updating each of the subsystem densities in so-called freeze-and-thaw cycles, 45 one obtains a subsystem-DFT scheme 24 that can be used as an efficient alternative to conventional Kohn-Sham (KS) DFT calculations. However, even though the frozen-density embedding potential is in principle exact (in the sense that it should lead to the same total electron density as a KS-DFT calculation on the full system), additional approximations are required for the kinetic-energy component of the embedding potentials.…”

“…These are based on the frozendensity embedding (FDE) scheme initially proposed by Wesolowski and Warshel 22 (following earlier work by Senatore and Subbaswamy 23 and by Cortona 24 ) and its extension to WFT-in-DFT embedding, first proposed by Carter and coworkers. [25][26][27][28] Particularly for such quantum-chemical multiscale simulations one encounters very complex workflows that are beyond the capabilities of standard tools.…”

Importance of dispersion in density functional calculations of cesium chloride and its related halides

“…This is only a marginal quantitative improvement over a previous spherical ion result (0.13 eV) obtained by Cortona. 9 Further investigations examined whether treating the heavier Cs ions relativistically would improve the result, but this failed to alter the finding. 10 Pyper has suggested 11 that dispersion plays an important role in stabilizing the B2 phase in CsCl, and his most recent calculations 12 using the relativistic integrals program 15,16 predict that the B2 phase is 0.078 eV/f.u.…”

“…[7][8][9][10][11][12][13][14] Many of these studies have employed approximate methods, rather than a full quantum mechanical treatment. For example, the self-consistent atomic deformation method 8 has been employed to compute the relative energy of these two structures for the alkali-metal halides.…”