Rotational motion in liquid water is anisotropic: a nuclear magnetic resonance and molecular dynamics simulation study.
Rotational motion in liquid water is anisotropic: a nuclear magnetic resonance and molecular dynamics simulation study.
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DOI：
10.1021/ja010312h
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发表时间：
2001-07
影响因子：
15
通讯作者：
J. Ropp;C. Lawrence;Thomas C. Farrar;James L. Skinner
中科院分区：
文献类型：
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作者：
J. Ropp;C. Lawrence;Thomas C. Farrar;James L. Skinner
在275 ~ 350 K的温度范围内，对富氘液态水的氘弛豫时间和（17）O T（1）弛豫时间进行了实验测量。这些弛豫时间可以产生适当的分子固定的单位矢量的旋转相关时间，如果四极耦合常数和不对称参数是已知的。我们确定后者从从头算研究水簇和实验化学位移测量。我们发现D（2）（16）O中OD键矢量的旋转相关时间从275 K的5.8 ps变化到350 K的0.86 ps，而D（2）（17）O中稀D（2）（16）O的面外矢量的旋转相关时间从275 K的4.4 ps变化到350 K的0.64 ps.这些结果表明，水的旋转运动是各向异性的。在较高温度下，液态水的分子动力学模拟与这些实验符合得很好，但在较低温度下，模拟结果比实验快得多。
Experimental NMR measurements of the deuterium and (17)O T(1) relaxation times in deuterium-enriched liquid water have been performed from 275 to 350 K. These relaxation times can yield rotational correlation times of appropriate molecule-fixed unit vectors if the quadrupole coupling constants and asymmetry parameters are known. We determine the latter from ab initio studies of water clusters and experimental chemical shift measurements. We find that the rotational correlation time for the OD bond vector in D(2)(16)O varies from 5.8 ps at 275 K to 0.86 ps at 350 K, and that the rotational correlation time for the out-of-plane vector of dilute D(2)(17)O in D(2)(16)O varies from 4.4 ps at 275 K to 0.64 ps at 350 K. These results indicate that the rotational motion of water is anisotropic. Molecular dynamics simulations of liquid water are in good agreement with these experiments at the higher temperatures, but the simulation results are considerably faster than experiment at the lower temperatures.