We discuss the origin of the so-called breathing instability of the BaBiO3 perovskite in view of the seemingly contradictory, results of the full-potential LDA calculations and the quasi-ionic (Potential-Induced Breathing, PIB) calculations. We demonstrate that both sets of results are in fact not in contradiction with, but rather complement, each other. In particular, a proper comparison of the LMTO and PIB calculations shows, to what extent the breathing instability is driven by the tendency of the Bi4+ ions to disproportionate into Bi3++Bi5+ (more correctly, into Bi4-x+Bi4+x), as had been suggested by some authors, and to what extent by the opening of the gap in Peierls' spirit.
 

(Conference Procees. Williamsburg Workshop, February 1994) Ferroelectrics, 164 169-75, 1995.