Fluctuations of local electric field and dipole moments in water between metal walls

摘要: We examine the thermal fluctuations of local electric field $E_k^{\rm loc}$ and dipole moment $\mu_k$ in liquid water at $T=298$ K between metal walls applied perpendicular direction. use analytic theory molecular dynamics simulation. In this situation, there is a global electrostatic coupling surface charges on polarization bulk. Then, correlation function density $p_z(r)$ along contains homogeneous part inversely proportional to cell volume $V$. Accounting for long-range dipolar interaction, we derive Kirkwood-Fr$\ddot{\rm{o}}$hlich formula when specimen $v$ much smaller than However, not small $v/V$, comes into play dielectric relations. also calculate distribution field. As unique feature water, its magnitude $|E_k^{\rm loc}|$ obeys Gaussian with large mean value $E_0 \cong 17~$V$/$nm, which arises mainly from surrounding hydrogen-bonded molecules. Since $|\mu_k|E_0\sim 30 k_{\rm B}T$, becomes mostly parallel loc}$. result, orientation distributions these two vectors nearly coincide, assuming classical exponential form. dynamics, component $\mu_k(t)$ loc}(t)$ changes timescale hydrogen bonds $\sim 5$ ps, while undergoes librational motions timescales 0.01 ps.