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arXiv 2104.03441physics.plasm-phphysics.comp-ph
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波包分子动力学研究热稠密物质的近似方法研究

An investigation into the approximations used in wave packet molecular dynamics for the study of warm dense matter

William A. Angermeier, Thomas G. White

摘要:

波包分子动力学(WPMD)作为一种快速的计算工具,在研究Born-Oppenheimer近似下的热稠密物质动力学过程中受到了广泛的关注。这些技术通常采用许多近似来实现计算效率,同时实现半经验缩放参数以保持准确性。我们调查三个主要的近似无处不在的WPMD:一个限制的基集,近似交换,缺乏相关性。我们检查每一个原子和分子的氢除了致密的氢等离子体中的这些近似。我们发现,最大的改进WPMD来自于结合两个高斯基础上的价键波函数的半经验校正。一个单一的参数缩放这种修正,以匹配实验压力的稠密氢。最终,我们发现,半经验的尺度参数是必要的,以纠正WPMD的主要近似。然而,减少更多从头算项的标度参数会得到更准确的结果,并更容易显示底层物理。

英文摘要:

Wave packet molecular dynamics (WPMD) has recently received a lot of attention as a computationally fast tool to study dynamical processes in warm dense matter beyond the Born-Oppenheimer approximation. These techniques, typically, employ many approximations to achieve computational efficiency while implementing semi-empirical scaling parameters to retain accuracy. We investigate three of the main approximations ubiquitous to WPMD: a restricted basis set, approximations to exchange, and the lack of correlation. We examine each of these approximations in atomic and molecular hydrogen in addition to a dense hydrogen plasma. We find that the biggest improvement to WPMD comes from combining a two Gaussian basis with a semi-empirical correction based on the valence-bond wave function. A single parameter scales this correction to match experimental pressures of dense hydrogen. Ultimately, we find that semi-empirical scaling parameters are necessary to correct for the main approximations in WPMD. However, reducing the scaling parameters for more ab-initio terms gives more accurate results and displays the underlying physics more readily.

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