arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0806.1193cond-mat.softcond-mat.mtrl-sci
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单原子液体中自动态响应的V-T理论

V-T Theory of Self Dynamic Response in a Monatomic Liquid

Giulia De Lorenzi-Venneri, Eric D. Chisolm, Duane C. Wallace

摘要:

利用振动-渡越(V-T)理论建立了一个新的自动态响应理论模型,并应用于液体钠从流体动力学状态到自由粒子极限的所有波矢q。在这个理论中,零阶哈密顿量描述了在一个单一的随机谷谐波扩展到无穷大的振动运动。这个哈密顿量是易处理的,是先验评估单原子液体,和相同的哈密顿量(相同的本征值和本征向量)用于平衡和非平衡理论。在这里,对于自中间散射函数Fself(q,t),我们发现在所有q处,通过短时间和中间时间,振动贡献与分子动力学(MD)几乎完全一致。这直接证实了在液体状态的运动中存在简正模振动相关。主要的过渡效果是振动平衡位置的扩散运动,因为液体在随机谷之间快速过渡。这种运动被建模为标准的随机行走,并且由此产生的理论Fself(q,t)在所有q和t处与MD结果非常一致。在q到无穷大的极限中,理论自动地显示出对自由粒子极限的正确逼近。同样在q为零的极限中,也出现了流体动力学极限。与广义流体力学和模式耦合的基准理论相比,本理论接近先验,同时实现适度更好的精度。因此,我们认为,这是对传统理论的改进。

英文摘要:

A new theoretical model for self dynamic response is developed using Vibration-Transit (V-T) theory, and is applied to liquid sodium at all wavevectors q from the hydrodynamic regime to the free particle limit. In this theory the zeroth-order Hamiltonian describes the vibrational motion in a single random valley harmonically extended to infinity. This Hamiltonian is tractable, is evaluated a priori for monatomic liquids, and the same Hamiltonian (the same set of eigenvalues and eigenvectors) is used for equilibrium and nonequlibrium theory. Here, for the self intermediate scattering function Fself(q,t) we find the vibrational contribution is in near perfect agreement with molecular dynamics (MD) through short and intermediate times, at all q. This is direct confirmation that normal mode vibrational correlations are present in the motion of the liquid state. The primary transit effect is diffusive motion of the vibrational equilibrium positions, as the liquid transits rapidly among random valleys. This motion is modeled as a standard random walk, and the resulting theoretical Fself(q,t) is in excellent agreement with MD results at all q and t. In the limit for q to infinity, the theory automatically exhibits the correct approach to the free-particle limit. Also in the limit for q to zero, the hydrodynamic limit emerges as well. In contrast to the benchmark theories of generalized hydrodynamics and mode coupling, the present theory is near a priori, while achieving modestly better accuracy. Therefore, in our view, it constitutes an improvement over the traditional theories.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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