#### Implicit Solvation Models in the FHI-AIMS Numeric Atomic Orbital Code

Harald Oberhofer (Chair for Theoretical Chemistry and Catalysis Research Center, TU München, Lichtenbergstr. 4, D-85747 Garching, Germany)

Numerous industrially relevant chemical reactions are critically influenced by

the effect of solvents. Yet, in order to make them computationally tractable,

most electronic structure calculations of such reactions tend to neglect

solvents completely. The large system sizes and sampling of solvent degrees of

freedom in explicit solvent simulations would preclude most ab-initio

simulation methods. For these reasons continuum solvation methods, first

pioneered over 80 years ago, are currently undergoing a renaissance.

In my talk I present two such models which we recently implemented in the

full-potential numeric atomic orbital code FHI-AIMS. The first of these is

based on the modified Poisson Boltzmann equation (MPBE) to fully account for

ionic and Stern-layer effects in addition to those of the solvent. Due to the

complexity of solving the non-linear MPBE this method adds a considerable

computational overhead to the respective ab-initio calculation. Our second

solvation method is therefore a more approximate solution of the generalised

Poisson equation based on a multipole expansion of the involved electrostatic

potentials.

Being effective models, both methods include a number of parameters influencing

the solvation cavity or non-electrostatic contributions, which need to be

determined beforehand. I will close my presentation with a summary of possible

approaches to determine solvent and ionic parameters and show that for solvents

where not enough experimental data exists a scaling relation can be employed to

yield an acceptable parameter set.