Development of Continuum Solvation Models
An invaluable part of the materials discovery process is in the development of improvements that extend the scope available for continuum / density functional theory (DFT) hybrid models. All developments are implemented in our ENVIRON software package.
Modeling the Diffuse Layer
Recent developments in the electric double layer have opened up the possibility for screening candidates for supercapacitors and fuel cells. Typically an electrolyte solution will form a layer over a conductive surface due to electrostatic attraction, which results in this so-called double layer. Typically this system is computationally expensive when dealt with atomistically, motivating a more viable continuum approach to the problem.
Fig. (above) shows an example of a system one can investigate using this approach. On the left, the atomistic picture (A) and on the right, the continuum picture (B). Metallic spheres represent Pt atoms, and between these surfaces lie water atoms and electrolyte ions (shown here as yellow and blue spheres).
Non-local Interface Models
There has been a recent push to develop non-local models that account for some of the additional effects in solvents not captured by the electrostatic equation. A critical component to continuum models is in deciding where the solvent exists. This is determined automatically based off the positions of the atoms (initially provided by the user), or the electronic density, which is obtained during the plane wave DFT simulation.
These simple definitions do not well capture more complex configurations. The solvent-aware model addresses this and provides a more robust definition of the solvent region. Another limitation is in the handling of charged systems. The field-aware model allows the solvent region to depend on the electric field produced by the system. These approaches can be thought of as additional tools in the Environ toolbox that expand the possibilities in material design.
These simple definitions do not well capture more complex configurations. The solvent-aware model addresses this and provides a more robust definition of the solvent region. Another limitation is in the handling of charged systems. The field-aware model allows the solvent region to depend on the electric field produced by the system. These approaches can be thought of as additional tools in the Environ toolbox that expand the possibilities in material design.