Semiquantum molecular dynamics simulation of liquid water by time-dependent Hartree approach.
Semiquantum molecular dynamics simulation of liquid water by time-dependent Hartree approach.
复制标题
通过依赖时间的 Hartree 方法对液态水进行半量子分子动力学模拟。
作者：
Hyeon;K. Ando
采用含时Hartree方法建立了半量子液态水分子动力学模拟。将经典的水分子内和分子间势函数推广到描述波包氢原子。推导并求解了包含辅助坐标和动量的扩展相空间运动方程。半量子水的分子动力学模拟表明，半量子氢原子使液态水结构化程度降低，氢键作用减弱。从水分子的迁移率增加和OH伸缩频率的红移推断出在液态水中结构化较差。由半量子氢引入的零点能增强了非谐势效应，并对红移的OH伸缩振动作出贡献。我们发现在吸收光谱中在4400 cm（-1）附近有一个明显的峰，这是由于WP宽度动力学与OH伸缩模和每个水的旋转运动之间的能量交换。我们认为半量子氢原子的存在使液体的自由能景观变得平滑，并影响液体的结构和动力学。
Semiquantum liquid water molecular dynamics simulation was developed using the time-dependent Hartree approach. The classical intra- and intermolecular potential functions of water were extended to describe the wave packet (WP) hydrogen atoms. The equations of motion with an extended phase space including auxiliary coordinates and momenta representing the hydrogen WP widths were derived and solved. The molecular dynamics simulation of semiquantum water demonstrated that the semiquantum hydrogen atoms make the liquid water less structured and the hydrogen bonds weakened. The poor structurization in liquid water was inferred from the increased mobility of a water molecule and the redshift of OH stretching frequency. The zero-point energy introduced by the semiquantum hydrogens enhances the anharmonic potential effects and contributes to the redshifted OH stretching vibration. We found a significant peak around 4400 cm(-1) in the absorption spectrum resulting from the energy exchange between the WP width dynamics and the coupling of the OH stretching mode and the rotational motion of each water. We proposed that a liquid free energy landscape is smoothed due to semiquantum hydrogen atoms, and influences the liquid structure and dynamics.