Computation of Dynamic Polarizabilities and van der Waals Coefficients from Path-Integral Monte Carlo,Journal of Chemical Theory and Computation

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Computation of Dynamic Polarizabilities and van der Waals Coefficients from Path-Integral Monte Carlo
Journal of Chemical Theory and Computation ( IF 5.7 ) Pub Date : 2018-10-02 00:00:00 , DOI: 10.1021/acs.jctc.8b00859
Juha Tiihonen ₁ , Ilkka Kylänpää ₁ , Tapio T. Rantala ₁

Affiliation

We demonstrate computation of total dynamic multipole polarizabilities using path-integral Monte Carlo method (PIMC). The PIMC approach enables accurate thermal and nonadiabatic mixing of electronic, rotational, and vibrational degrees of freedom. Therefore, we can study the thermal effects, or lack thereof, in the full multipole spectra of the chosen one- and two-electron systems: H, Ps, He, Ps₂, H₂, and HD⁺. We first compute multipole–multipole correlation functions up to octupole order in imaginary time. The real-domain spectral function is then obtained by analytical continuation with the maximum entropy method. In general, sharpness of the active spectra is limited, but the obtained off-resonant polarizabilities are in good agreement with the existing literature. Several weak and strong thermal effects are observed. Furthermore, the polarizabilities of Ps₂ and some higher multipole and higher frequency data have not been published before. In addition, we compute isotropic dispersion coefficients C₆, C₈, and C₁₀ between pairs of species using the simplified Casimir–Polder formulas.

中文翻译：

从路径积分蒙特卡罗计算动态极化率和范德华系数

我们演示了使用路径积分蒙特卡罗方法（PIMC）计算总动态多极极化率。PIMC方法可实现电子，旋转和振动自由度的精确热和非绝热混合。因此，我们可以研究所选的一电子系统和两电子系统的完整多极谱中的热效应或不存在的热效应：H，Ps，He，Ps ₂，H ₂和HD ⁺。我们首先在假想时间内计算多极-多极相关函数，直到八极阶。然后通过使用最大熵方法的解析连续性获得实域谱函数。通常，活性光谱的清晰度是有限的，但是获得的非共振极化率与现有文献非常吻合。观察到了几种弱和强热效应。此外，Ps ₂的极化率以及一些更高的多极点和更高频率的数据以前尚未公布。此外，我们使用简化的Casimir-Polder公式计算物种对之间的各向同性弥散系数C ₆，C ₈和C ₁₀。

更新日期：2018-10-02

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