Chandrachud Prachi
UM-DAE Centre for Excellence in Basic Sciences, Mumbai University, Mumbai 400032, India.
J Phys Condens Matter. 2015 Nov 11;27(44):445502. doi: 10.1088/0953-8984/27/44/445502. Epub 2015 Oct 9.
We report the results of ab initio molecular dynamics simulations of Ga13 and Ga17 clusters confined inside carbon nanotubes with different diameters. The cluster-tube interaction is simulated by the Lennard-Jones (LJ) potential. We discuss the geometries, the nature of the bonding and the thermodynamics under confinement. The geometries as well as the isomer spectra of both the clusters are significantly affected. The degree of confinement decides the dimensionality of the clusters. We observe that a number of low-energy isomers appear under moderate confinement while some isomers seen in the free space disappear. Our finite-temperature simulations bring out interesting aspects, namely that the heat capacity curve is flat, even though the ground state is symmetric. Such a flat nature indicates that the phase change is continuous. This effect is due to the restricted phase space available to the system. These observations are supported by the mean square displacement of individual atoms, which are significantly smaller than in free space. The nature of the bonding is found to be approximately jellium-like. Finally we note the relevance of the work to the problem of single file diffusion for the case of the highest confinement.
我们报告了限制在不同直径碳纳米管内的Ga13和Ga17团簇的从头算分子动力学模拟结果。团簇与碳纳米管之间的相互作用通过 Lennard-Jones（LJ）势进行模拟。我们讨论了受限条件下的几何结构、键合性质和热力学性质。两种团簇的几何结构以及异构体光谱都受到了显著影响。受限程度决定了团簇的维度。我们观察到，在适度受限条件下会出现许多低能异构体，而在自由空间中出现的一些异构体则消失了。我们的有限温度模拟揭示了一些有趣的方面，即尽管基态是对称的，但热容曲线是平坦的。这种平坦的性质表明相变是连续的。这种效应是由于系统可用的相空间受到限制所致。这些观察结果得到了单个原子均方位移的支持，其均方位移明显小于自由空间中的情况。发现键合性质近似于类电子气。最后，我们指出了这项工作对于最高受限情况下单分子扩散问题的相关性。
