Nature Materials 6, 122-128 (2007) doi: 10.1038/nmat1807

The authors wish to cite an extra reference to adjoin reference 19:

Dronskowski, R. & Blöchl, P. E. Crystal orbital Hamilton populations (COHP): energy-resolved visualization of chemical bonding in solids based on density-functional calculations. J. Phys. Chem. 97, 8617–8624 (1993).