Role of Conduction Electrons in the ortho-KC${}_{60}$ Polymer

Abstract

We present first-principles band calculations as well as structural optimization of the orthorhombic K${}_1$C${}_{60}$ polymerized phase. We found three-dimensional inter-fullerene bonding/anti-bonding characters consisting of $t_{1u}$ molecular orbitals with $p$-like symmetry in the conduction bands. The formation of the four-membered ring connecting the fullerenes lifts the $p_x$ band from the continuous $p_y$-$p_z$ band, where the z-axis is parallel to the chain. The asymmetry between $p_x$ and $p_y$ may play an important role in binding the chains with the rotational configuration proposed by Stephens et al.

8 pages, 1 JPG figure, 4 Color JPG figures, uses REVTEX. Submitted to Phys.Rev.Lett