Sound propagation in liquid water: The puzzle continues
Sound propagation in liquid water: The puzzle continues
复制标题
液态水中的声音传播：谜题仍在继续
DOI：
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发表时间：
1994
期刊：
影响因子：
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通讯作者：
S. Sastry
中科院分区：
文献类型：
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作者：
F. Sciortino;S. Sastry
对水中声传播的实验和模拟研究已经观察到，在大波矢量k（k <$0.25 A-1）处，纵向声模式的速度约为3500 m/s，是水动力声速的两倍多。流体动力学声音模式和高频模式之间的关系一直是对比解释的中心。在本文中，我们报告了广泛的分子动力学模拟特设探索集体光谱的中间和低k部分。我们计算了在0.026到1 A−1的温度范围内纵向和横向集体模的色散关系。在所研究的所有温度下，声速随k而增加。在最高的研究温度下，声速的变化值相比，流体动力学声速的中子散射实验所观察到的。我们表明，粘弹性近似描述的数据令人满意。我们还对淬火液体结构进行了简正模分析，以获得有关在中频（50-100 cm−1）下观察到的行为的进一步信息。我们发现在这些频率和迹象表明，与本地化模式的声音分支的相互作用，这种分散的起源，进一步积极的分散的声音分支。
Experimental and simulation studies of sound propagation in water have observed, at large wave vectors k (k≳0.25 A−1), a longitudinal sound mode with a velocity of about 3500 m/s, more than twice the hydrodynamic sound velocity. The relation between the hydrodynamic sound mode and the high frequency mode has been the center of contrasting interpretations. In this paper, we report extensive molecular dynamics simulations designed ad hoc to explore the intermediate and low k part of the collective spectrum. We calculate the dispersion relations for longitudinal and transverse collective modes from 0.026 to 1 A−1 for a range of temperatures. At all temperatures studied, the sound velocity increases with k. At the highest studied temperature, the sound velocity changes from values comparable to hydrodynamic sound velocity to ones observed by neutron scattering experiments. We show that the viscoelastic approximation describes the data satisfactorily. We also perform normal mode analysis of quenched liquid configurations to obtain further information about the behavior observed at intermediate frequencies (50–100 cm−1). We find further positive dispersion of the sound branch at these frequencies and indications which suggest the interaction of the sound branch with localized modes as the origin of such dispersion.