University of Tennessee/Oak Ridge National Laboratory Center for Molecular Biophysics, 6011 Bethel Valley Rd, Oak Ridge, Tennessee 37830, USA.
J Chem Phys. 2011 Oct 7;135(13):134507. doi: 10.1063/1.3643077.
The electric field dependence of the structure and dynamics of water at 77 K, i.e., below the glass transition temperature (136 K), is investigated using molecular dynamics simulations. Transitions are found at two critical field strengths, denoted E(1) and E(2). The transition around E(1)≈3.5 V/nm is characterized by the onset of significant structural disorder, a rapid increase in the orientational polarization, and a maximum in the dynamical fluctuations. At E(2)≈40 V/nm, the system crystallizes in discrete steps into a body-centered-cubic unit cell that minimizes the potential energy by simultaneous superpolarization of the water molecular dipoles and maximization of the intermolecular hydrogen bonds. The stepwise and discontinuous increase of the orientational polarization with the increasing electric field indicates that the dipole relaxation in the electric field is highly cooperative.
使用分子动力学模拟研究了 77 K（即玻璃化转变温度 136 K 以下）下水的结构和动力学对电场的依赖性。在两个临界场强 E(1) 和 E(2) 处发现了转变。约 3.5 V/nm 的 E(1)处的转变以显著的结构无序、取向极化的快速增加和动力学波动的最大值为特征。在约 40 V/nm 的 E(2)处，系统以离散的步骤结晶成体心立方单胞，通过水分子偶极子的同时超极化和分子间氢键的最大化来最小化势能。随着电场的增加，取向极化呈阶梯式和不连续增加，表明偶极子在电场中的弛豫具有高度的协同性。
