Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano, Italy.
J Phys Chem A. 2011 Jun 30;115(25):7300-9. doi: 10.1021/jp200617a. Epub 2011 May 23.
Path integral Monte Carlo calculations of (4)He nanodroplets doped with alkali (Na(+), K(+) and Cs(+)) and alkali-earth (Be(+) and Mg(+)) ions are presented. We study the system at T = 1 K and between 14 and 128 (4)He atoms. For all studied systems, we find that the ion is well localized at the center of the droplet with the formation of a "snowball" of well-defined shells of localized (4)He atoms forming solid-like order in at least the first surrounding shell. The number of surrounding helium shells (two or three) and the number of atoms per shell and the degree of localization of the helium atoms are sensitive to the type of ion. The number of (4)He atoms in the first shell varies from 12 for Na(+) to 18 for Mg(+) and depends weakly on the size of the droplet. The study of the density profile and of the angular correlations shows that the local solid-like order is more pronounced for the alkali ions with Na(+) giving a very stable icosahedral order extending up to three shells.
本文呈现了（4）He 纳米液滴掺杂碱（Na(+)、K(+)和 Cs(+)）和碱土（Be(+)和 Mg(+)）离子的路径积分蒙特卡罗计算。我们在 T = 1 K 下研究了 14 到 128 个（4）He 原子之间的系统。对于所有研究的系统，我们发现离子很好地定位于液滴中心，形成具有明确定义壳层的“雪球”，至少在第一个壳层中形成固态有序的局域（4）He 原子。围绕氦原子的壳层数（两个或三个）、每个壳层中的原子数和氦原子的局域化程度对离子的类型敏感。第一壳层中的（4）He 原子数从 Na(+)的 12 个变化到 Mg(+)的 18 个，并且与液滴的大小弱相关。密度分布和角相关的研究表明，对于具有 Na(+)的碱离子，局部固态有序更为明显，给出了非常稳定的扩展到三个壳层的二十面体有序。
