The static dielectric constant of liquid water is computed using classical force field based molecular dynamics simulation at fixed electric displacement $\mathbf{D}$. The method to constrain the electric displacement is the finite-temperature classical variant of the constant $\mathbf{D}$ method developed by Stengel, Spaldin, and Vanderbilt [Nat. Phys. 5, 304 (2009)]. There is also a modification of this scheme imposing fixed values of the macroscopic field $\mathbf{E}$. The method is applied to the popular SPC/E model of liquid water. We compare four different estimates of the dielectric constant, two obtained from fluctuations of the polarization at $\mathbf{D}=0$ and $\mathbf{E}=0$ and two from the variation of polarization with finite $\mathbf{D}$ and $\mathbf{E}$. It is found that all four estimates agree when properly converged. The computational effort to achieve convergence varies, however, with constant $\mathbf{D}$ calculations being substantially more efficient. We attribute this difference to the much shorter relaxation time of longitudinal polarization compared to transverse polarization accelerating constant $\mathbf{D}$ calculations.

• Received 17 December 2015

DOI:https://doi.org/10.1103/PhysRevB.93.144201