Linearized Orbital-Free Embedding Potential in Self-Consistent Calculations

Conventionally, solving one-electron equations for embedded orbitals [Eqs. (20) and (21) in Wesolowski and Warshel, J Phys Chem, 1993, 97, 8050] proceeds by a self-consistent procedure in which the whole effective potential, including its embedding component, is updated in each iteration. We propose an alternative scheme (splitSCF), which uses the linearized embedding potential in the inner iterative loop and the outer-loop is used to account for its deviations from linearity. The convergence of the proposed scheme is investigated for a set of weakly bound intermolecular complexes representing typical interactions with the environment. The outer loop is shown to converge very fast. No more than 3-4 iterations are needed. Errors due to skipping the outer loop completely and using the electron density obtained in the absence of the environment in the linearized embedding potential are investigated in detail. It is shown that this computationally attractive simplification, used already in numerical simulations by others, is adequate not only for van der Waals and hydrogen-bonded complexes but even if the complex comprises charged components, i.e., where strong electronic polarization takes place. In charge-transfer type of complexes, larger changes of electron of density upon complex formation occur and the above simplification is not recommended.