Science. 1992 Dec 18;258(5090):1916-8. doi: 10.1126/science.258.5090.1916.
The structural and electronic properties of the La@C(82) fullerene have been investigated by means of the Car-Parrinello method, which is based on the local density approximation of the density functional theory. The topological arrangement of the C(82) cage was assumed to be a C(3v) symmetry isomer. Three configurations were considered, one with the lanthanum atom at the center of the cluster, one with it along the threefold axis, and one with it at a low-symmetry, highly coordinated site. The structure was fully relaxed and it was found that the last of these configurations is energetically preferred. In this position, the lanthanum atom is nearly in a La(3+) state and the unpaired electron is somewhat delocalized on the cage, in agreement with available experimental data. This arrangement suggests that the chemical shifts of the 5s and 5p lanthanum states can be used as a structural probe and as a way of further validating this picture. It is argued that this conclusion is not affected by the assumed fullerene structure.
采用基于密度泛函理论的局域密度近似的 Car-Parrinello 方法研究了 La@C(82)富勒烯的结构和电子性质。假定 C(82)笼的拓扑排列为 C(3v)对称异构体。考虑了三种构型，一种是镧原子位于团簇中心，一种是沿着三重轴，一种是位于低对称、高配位的位置。对结构进行了完全松弛，结果发现最后一种构型在能量上是有利的。在这个位置上，镧原子几乎处于 La(3+)状态，不成对电子在笼上有一定程度的离域，这与现有实验数据一致。这种排列表明，5s 和 5p 镧态的化学位移可以用作结构探针，并进一步验证这种图像。有人认为，这一结论不受假定的富勒烯结构的影响。
