Ar_3团簇的虚时间高斯动力学
Imaginary time Gaussian dynamics of the Ar_3 cluster
摘要：
玻尔兹曼算符的半经典高斯近似已成为研究低温下原子团簇热力学性质的重要工具。通常，应用数值上昂贵的解冻高斯变量。在这篇文章中，我们介绍了一个数值上更便宜的冻结高斯近似的虚时间传播与宽度矩阵，特别适合于集群的动力学。结果的质量是解冻高斯方法的基础上的单粒子的animals。我们将该方法应用于氩三聚体，研究了原子团簇的解离过程。结果清楚地表明，在温度T ~ 20 K下，从一个有界部分到三个自由粒子的经典过渡，而以前的研究系统无法解决这种过渡。量子效应，即，与纯经典情况的差异表现在平均能量和比热的低温行为以及转变温度的轻微偏移。我们还讨论了通常引入收敛数值计算的原子的人工约束的影响。结果表明，在团簇研究中经常采用的限制性约束对团簇的热力学性质有很大的影响。这一发现可能对原子团簇的其他研究有启示作用。
英文摘要：
Semiclassical Gaussian approximations to the Boltzmann operator have become an important tool for the investigation of thermodynamic properties of clusters of atoms at low temperatures. Usually, numerically expensive thawed Gaussian variants are applied. In this article, we introduce a numerically much cheaper frozen Gaussian approximation to the imaginary time propagator with a width matrix especially suited for the dynamics of clusters. The quality of the results is comparable to that of thawed Gaussian methods based on the single-particle ansatz. We apply the method to the argon trimer and investigate the dissociation process of the cluster. The results clearly show a classical-like transition from a bounded moiety to three free particles at a temperature T ~ 20 K, whereas previous studies of the system were not able to resolve this transition. Quantum effects, i.e., differences with the purely classical case manifest themselves in the low-temperature behavior of the mean energy and specific heat as well as in a slight shift of the transition temperature. We also discuss the influence of an artificial confinement of the atoms usually introduced to converge numerical computations. The results show that restrictive confinements often implemented in studies of clusters can influence the thermodynamic properties drastically. This finding may have implications on other studies of atomic clusters.
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