Whilst clusters of carbon atoms are well-known, my eye was caught by a recent article describing the detection of a cluster of boron atoms, B40 to be specific. My interest was in how the σ and π-electrons were partitioned. In a C40, one can reliably predict that each carbon would contribute precisely one π-electron. But boron, being more electropositive, does not always play like that. Having one electron less per atom, one might imagine that a fullerene-like boron cluster would have no π-electrons. But the element has a propensity to promote its σ-electrons into the π-manifold, leaving a σ-hole. So how many π-electrons does B40 have? These sorts of clusters are difficult to build using regular structure editors, and so coordinates are essential. The starting point for a set of coordinates with which to compute a wavefunction was the supporting information. Here is the relevant page: The coordinates are certainly there (that is not always the case), but you have to know a few tricks to make them usable.
- H. Zhai, Y. Zhao, W. Li, Q. Chen, H. Bai, H. Hu, Z.A. Piazza, W. Tian, H. Lu, Y. Wu, Y. Mu, G. Wei, Z. Liu, J. Li, S. Li, and L. Wang, "Observation of an all-boron fullerene", Nature Chemistry, 2014. http://dx.doi.org/10.1038/nchem.1999
- H.S. Rzepa, "The distortivity of π-electrons in conjugated boron rings", Physical Chemistry Chemical Physics, vol. 11, pp. 10042, 2009. http://dx.doi.org/10.1039/B911817A