简单液体局域密度动力学的自洽描述。熔融锂的例子
Self-Consistent Description of Local Density Dynamics in Simple Liquids. The Case of Molten Lithium
摘要：
动态结构因子是可以通过布里渊光散射以及中子和X射线的非弹性散射测量的量。动态结构因子的谱（或频率）矩直接定义了散射定律的求和规则。在这项研究中制定的理论方案允许一个描述简单的液体中的局部密度波动的动力学，并获得的频谱矩的动态结构因子的表达式。该理论满足所有的总和规则，并获得的动态结构因子的表达式产生正确的外推到流体动力学的限制，以及到自由粒子动力学的限制。我们讨论了这个理论与广义流体力学和粘弹性模型，这是常用的非弹性中子和X射线在液体中散射的数据进行分析的对应关系。特别是，我们揭示了记忆函数的粘弹性模型的假设条件，可以直接在所提出的理论。在此基础上计算了液态锂的动态结构因子，并对散射谱的各种特征进行了评价。结果表明，理论计算结果与非弹性X射线散射数据符合较好。
英文摘要：
The dynamic structure factor is the quantity, which can be measured by means of Brillouin light-scattering as well as by means of inelastic scattering of neutrons and X-rays. The spectral (or frequency) moments of the dynamic structure factor define directly the sum rules of the scattering law. The theoretical scheme formulated in this study allows one to describe the dynamics of local density fluctuations in simple liquids and to obtain the expression of the dynamic structure factor in terms of the spectral moments. The theory satisfies all the sum rules, and the obtained expression for the dynamic structure factor yields correct extrapolations into the hydrodynamic limit as well as into the free-particle dynamics limit. We discuss correspondence of this theory with the generalized hydrodynamics and with the viscoelastic models, which are commonly used to analyze the data of inelastic neutron and X-ray scattering in liquids. In particular, we reveal that the postulated condition of the viscoelastic model for the memory function can be directly obtained within the presented theory. The dynamic structure factor of liquid lithium is computed on the basis of the presented theory, and various features of the scattering spectra are evaluated. It is found that the theoretical results are in agreement with inelastic X-ray scattering data.
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