Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748, Garching, Germany.
J Phys Chem A. 2011 Jun 30;115(25):6831-7. doi: 10.1021/jp110524p. Epub 2011 Feb 3.
We present results of a theoretical study of structural and superfluid properties of parahydrogen (p-H(2)) clusters comprising 25, 26, and 27 molecules at low temperature. The microscopic model utilized here is based on the Silvera-Goldman pair potential. Numerical results are obtained by means of quantum Monte Carlo simulations, making use of the continuous-space worm algorithm. The clusters are superfluid in the low temperature limit, but display markedly different physical behaviors. For N = 25 and 27, superfluidity at low temperature arises as clusters melt, that is, become progressively liquid-like as a result of quantum effects. On the other hand, for N = 26, the cluster remains rigid and solid-like. We argue that the cluster (p-H(2))(26) can be regarded as a mesoscopic "supersolid". This physical picture is supported by results of simulations in which a single p-H(2) molecule in the cluster is isotopically substituted.
我们呈现了对由 25、26 和 27 个分子组成的低温-parahydrogen(p-H(2))团簇的结构和超流性质的理论研究结果。这里使用的微观模型基于 Silvera-Goldman 对势。数值结果是通过量子蒙特卡罗模拟获得的，利用连续空间虫算法。在低温极限下，团簇是超流体的，但表现出明显不同的物理行为。对于 N = 25 和 27，低温下的超流性是由于团簇熔化引起的，也就是说，由于量子效应，团簇逐渐变得液态。另一方面，对于 N = 26，团簇保持刚性和固态。我们认为，团簇(p-H(2))(26)可以被视为一种介观“超固体”。这种物理图像得到了模拟结果的支持，其中在团簇中单个 p-H(2)分子被同位素取代。
