Dielectric properties of nano-confined water: a canonical thermopotentiostat approach*

With the advent of robust techniques to apply electric fields in density-functional calculations, there has been continuous interest to use ab initio molecular dynamics (MD) simulations to study electrically triggered processes, such as electrochemical reactions. Here we introduce a novel approach to sample the canonical ensemble at constant temperature and applied electric potential. Our thermopotentiostat approach can be straightforwardly implemented into any density-functional code. Using thermopotentiostat MD simulations, we compute the dielectric constant of nano-confined water without any assumptions for the dielectric volume. These simulations reveal the existence of a dielectrically dead layer within interfacial water.