SDS

SDS forms microstructures (micelles) at most accessible simulation conditions. This presents some interesting questions in its modeling.

This case study uses the following coarse-grained mapping:

SDS

where every 2 tail carbon beads are grouped to a single bead, and the entire \(SO_4^-\) head group is mapped to a single bead.

The case study also builds off of water, dodecane, and NaCl interactions derived following previous case studies. As outlined in the theoretical considerations, this takes some care in choosing a coarse graining ensemble. For reproducibile structuring we deposit SDS at a dodecane-water interface:

dodecane-water-SDS

(The bounding boxes above outline the dodecane region sandwiched between two SDS interfacial layers.)

Code can be found in the repository. See the jupyter notebook implementing this in coarse graining. The main new feature being done is the addition of a surface area constraint:

Az = sim.measure.Az(Sys0,axis=2)
Az_target = 18.8556366
Sys0.Measures.append(Az)
Opt0.MinReweightFrac = 0.25
StageCoefsA = [100.0,100.0]
UDist0 = Opt0.AddPenalty(Az, Az_target, MeasureScale = 1., Coef=1.e-80)

To run with the constraints, the optimization command is now:

Opt0.RunStages(StageCoefs = StageCoefsA, LagMult0=10.0)