electric field exemple     
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3D box with a model electrode which has the structure of NaCl and an aqueous NaCl electrolyte.
NVT simulation at finite electric field, solved using conjugate gradient

Typical input from:
- Dufils, Jeanmairet, Rotenberg, Sprik, Salanne
Simulating Electrochemical Systems by Combining the Finite Field Method with a Constant Potential Electrode
Phys. Rev. Lett., 123, 195501, 2019
