Magnetic properties of Cr_2O_n~- clusters: A theoretical study.

摘要

The chromium ions in each of the chromium oxide cluster anions Cr_2O~-, Cr_2O_2~- and Cr_2O_3~- have been found to be ferro-magnetically coupled to each other. In each case, one of the highest spin states is the ground state. In fact, the ground states correspond to the spin multiplicities 10, 10 and 8, respectively. The magnetic interaction proceeds via super exchange mechanism. The intra-molecular ferromagnetic exchange coupling constant is estimated from the density functional methodology using broken symme_try approach. It is found to decrease steadily with increasing number of oxygen atoms. A rationale for this phenomenon can be given from molecular orbital analysis.