Experimental evidence of orbital order inα-B12andγ-B28

Abstract

The electron density of the α form of boron has been obtained by multipole refinement against high-resolution, single-crystal x-ray diffraction data measured on a high-quality single crystal at a temperature of 100 K. Topological properties of this density have been used to show that all chemical bonds between B 12 clusters in α-B 12 are formed due to one orbital on each boron atom that is oriented perpendicular to the surface of the cluster. It is shown that the same orbital order on B 12 clusters persists in both α-B 12 and γ-B 28 polymorphs and in several dodecaboranes, despite the fact that in every case the B 12 clusters participate in entirely different kinds of exocluster bonds. It is likely that the same orbital order of B 12 clusters can explain bonding in other boron polymorphs and boron-rich solids.

Revisit: High resolution charge density study of α-rhombohedral boron using third-generation SR data at SPring-8

“…These values are consistent with a recent study by S. Mondal et al [7]. B p and B e indicate the polar and equatorial atom, respectively.…”

“…The distances distributed from 1.6676(4) to 2.0105(4) Å, which are very similar to the results of the reference studies [6,7].…”

“…2b. This bond has been observed in the previous MEM charge densities [4,5], recent multipole result [7] and theoretical studies [3].…”

“…bond has been observed in the previous charge density studies [4][5][6][7] and the recent theoretical calculation [3]. Weak 3c bond is recognized in Fig.…”

Electron Density Studies in Materials Research

“…In the second study of α‐B 12 , the bonding pattern within the icosahedra was shown to be very similar in the two polymorphs . Furthermore, the inter‐icosahedral bonding was shown to consist of both strong 2c2e bonds (in fact the strongest bonds in the material) and weaker 3c2e bonds.…”