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A model for transits in dynamic response theory

机译：动态响应理论中的过境模型

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The first goal of vibration-transit (V-T) theory was to construct a tractable approximate Hamiltonian from which the equilibrium thermodynamic properties of monatomic liquids can be calculated. The Hamiltonian for vibrations in an infinitely extended harmonic random valley, together with the universal multiplicity of such valleys, gives an accurate first-principles account of the measured thermodynamic properties of the elemental liquids at melt. In the present paper, V-T theory is extended to nonequilibrium properties, through an application to the dynamic structure factor S(q,omega). It was previously shown that the vibrational contribution alone accurately accounts for the Brillouin peak dispersion curve for liquid sodium, as compared both with molecular-dynamics (MD) calculations and inelastic x-ray scattering data. Here it is argued that the major effects of transits will be to disrupt correlations within the normal-mode vibrational motion and to provide an additional source of inelastic scattering. We construct a parametrized model for these effects and show that it is capable of fitting MD results for S(q,omega) in liquid sodium. A small discrepancy between model and MD at large q is attributed to multimode vibrational scattering. In comparison, mode coupling theory formulates S(q,omega) in terms of processes through which density fluctuations decay. While mode coupling theory is also capable of modeling S(q,omega) very well, V-T theory is the more universal since it expresses all statistical averages, thermodynamic functions, and time correlation functions alike, in terms of the same motional constituents, vibrations and transits. (c) 2005 American Institute of Physics.
机译：振动传递（V-T）理论的首要目标是构建一个易于计算的近似哈密顿量，从中可以计算出单原子液体的平衡热力学性质。无限扩展的谐波随机谷中的振动的哈密顿量，以及此类谷的普遍多重性，给出了在熔体中测得的元素液体热力学性质的准确的第一性原理。在本文中，V-T理论通过将其应用于动态结构因子S（q，omega）扩展到了非平衡性质。先前已证明，与分子动力学（MD）计算和非弹性X射线散射数据相比，仅振动贡献就可以准确解释液态钠的布里渊峰色散曲线。这里认为，过渡的主要作用将是破坏正常模式振动运动中的相关性，并提供非弹性散射的另一个来源。我们针对这些效应构建了参数化模型，并表明它能够拟合液态钠中S（q，omega）的MD结果。模型与MD在较大q处的微小差异是由于多模振动散射引起的。相比之下，模式耦合理论根据密度波动衰减的过程来公式化S（q，ω）。虽然模式耦合理论也能够很好地建模S（q，omega），但是VT理论却更为通用，因为它以相同的运动成分，振动和振动来表示所有统计平均值，热力学函数和时间相关函数。过境。 （c）2005年美国物理研究所。

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