Idowu Saheed, Boninsegni Massimo
Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E7, Canada.
J Chem Phys. 2015 Apr 7;142(13):134303. doi: 10.1063/1.4916616.
We study by computer simulations the effect of confinement on the superfluid properties of small two-dimensional (2D) parahydrogen clusters. For clusters of fewer than twenty molecules, the superfluid response in the low temperature limit is found to remain comparable in magnitude to that of free clusters, within a rather wide range of depth and size of the confining well. The resilience of the superfluid response is attributable to the "supersolid" character of these clusters. We investigate the possibility of establishing a bulk 2D superfluid "cluster crystal" phase of p-H2, in which a global superfluid response would arise from tunnelling of molecules across adjacent unit cells. The computed energetics suggests that for clusters of about ten molecules, such a phase may be thermodynamically stable against the formation of the equilibrium insulating crystal, for values of the cluster crystal lattice constant possibly allowing tunnelling across adjacent unit cells.
我们通过计算机模拟研究了限制条件对小型二维（2D）仲氢团簇超流性质的影响。对于分子数少于二十个的团簇，发现在相当宽的限制阱深度和尺寸范围内，低温极限下的超流响应在量级上与自由团簇的超流响应相当。超流响应的弹性归因于这些团簇的“超固体”特性。我们研究了建立p-H₂的体相二维超流“团簇晶体”相的可能性，其中全局超流响应将由分子在相邻晶胞间的隧穿产生。计算得到的能量学结果表明，对于约十个分子的团簇，对于可能允许分子在相邻晶胞间隧穿的团簇晶格常数取值，这样的相相对于平衡绝缘晶体的形成在热力学上可能是稳定的。
