Effects of Solvent Density Distribution and Dipole-Dipole Interaction on a Polarization Fluctuation near an Electrically Neutral Surface (vol 91, 114602, 2022)

To understand the physical mechanism of the decrease in the dielectric constant of water near a hydrophobic surface, we calculate a polarization fluctuation in polar solvent molecules around an electrically neutral solute particle. We develop a theory on the basis of the linear response theory with the density functional theory so that we can calculate the polarization fluctuation by treating the density distribution of solvent molecules as an input. The polarization fluctuation calculated using the solvent density distribution obtained from the molecular dynamics (MD) simulations decreases near the solute particle where the solvent density is lower than that in the bulk, which is in agreement with the MD result. To study the effect of the solvent dipole-dipole interaction, we use a spatially constant solvent density outside the solute particle. The polarization fluctuation also decreases in this case, indicating that the absence of solvent molecules inside the solute particle (i.e., the excluded volume effect) reduces the solvent dipole-dipole correlation outside the solute.