Interior Melting of the C3B16 and C2B14− Clusters Between 1000 K and 2000 K

[摘要] For bulk three-dimensional materials, it is common for the surface to melt at a slightly lower temperature than the bulk. This is known as surface melting, and is typically due to the fact that there are fewer bonds to surface atoms. However, for small clusters, this picture can change. In recent years, there have been investigations of the B19 and B19− clusters, which show striking diffusive behavior as they are heated to 1000 K. We wondered what the effect of substituting a few carbon atoms would be on the properties of these small clusters. To this end, we carried out extensive structural searches and molecular dynamics simulations to study the properties of C3B16 and C2B14− at elevated temperatures. The ground state structures and lowest energy isomers for these clusters were determined and calculated. The lowest energy structures are two-dimensional with vacancies inside. The C atoms are located in the outer ring in the ground state. At 1400 K, the outer rim containing the carbon atoms has fixed bonding, while the interior atoms are able to diffuse freely. Therefore, both of these clusters display interior melting at 1400 K. This interior melting is explained by the larger bond strength of the rim atoms. Molecular dynamics simulations at 3000 K showed complete melting and we observed a wide variety of configurations in both clusters.

[学科分类] 凝聚态物理

[关键词] boron clusters;boron-carbon mixed clusters;density functional theory;melting