INTERACTION OF DOPANT CATIONS WITH 4-1 DEFECT CLUSTERS IN NONSTOICHIOMETRIC 3D TRANSITION-METAL MONOXIDES - A THEORETICAL-STUDY

The ASED-MO theory and a normalized ion energy model have been used to study the energetics of substitutional dopants in Mn, Fe, Co, and Ni non-stoichiometric monoxides; we find that certain dopants stabilize 4:1 defect clusters (4 octahedral M**2** plus vacancies surrounding an M**3**30 tetrahedral interstitial). For example, Fe**3** plus -based 4:1 clusters in Mn//1// minus //xO and Mn**3** plus -based 4:1 clusters in Fe//1// minus //xO have comparable stabilities to those in the undoped materials, while Mn**3** plus - and Fe**3** plus -based 4:1 clusters in Co//1// minus //xO and Ni//1// minus //xO are significantly more stable than those in the undoped oxides. Cr**3** plus has a strong octahedral site preference energy in all cases, which prevents formation of doped 4:1 defect clusters. Despite a strong tetrahedral site preference energy, Zn**2** plus does not cause formation of 4:1 clusters because they would destabilize oxygen 2p orbitals.