标题： 稳定的薄笼状层 显示英文标题

标题： Stable Thin Clathrate Layers

摘要： 我们研究了元素Si、Ge和Sn在金刚石、笼形结构和其他竞争结构中的自由悬浮薄层，并通过比较相同原子/面积覆盖下的Kohn-Sham总能来评估它们的稳定性$\rho$。 我们发现，在3-6 ML范围内（以金刚石单层为单位），表面能使得笼形结构相对于体相稳定的金刚石结构或其他竞争结构更加稳定，对于所有三种元素都是如此。 在1.3-1.6 ML覆盖范围内，Si和Ge的稳定层是波纹六边形晶格的原子装饰，形成具有矩形单元的哑铃状装饰模式。 类似的，Sn层不稳定，形成由相互连接的Sn$_9$集群组成的网状结构。 在2.3 ML覆盖范围内，Sn的金属双层结构完成了稳定薄层非金刚石结构的多样性。 显示英文摘要

摘要： We explore elemental Si, Ge and Sn free-standing slabs in diamond, clathrate and other competing structures and evaluate their stability by comparing Kohn-Sham total energies at the same atoms/area coverage $\rho$. We find that within 3-6 ML range (in units of diamond monolayer), the surface energy stabilizes clathrates against the bulk-stable diamond structure or other competitors, for all three elements. At~1.3-1.6 ML coverages, Si and Ge stable layers are adatomic decorations of the puckered honeycomb lattice, forming a dumbbell--decorated pattern with rectangular unit cell. Analogical Sn layer is unstable to a web-like net of interconnected Sn$_9$ clusters. The zoo of stable thin-layer non-diamond structures is completed by a Sn metallic bilayer at 2.3 ML coverage.