Preferred compounds include {HEAD ~ Bi oxide}, {TAIL ~ Co oxide}, Cu oxide, Fe oxide, Mn oxide, and Pr oxide, and optionally Ag oxide 
Preferred compounds include { HEAD ~ Bi oxide } , { TAIL ~ Co oxide } , Cu oxide , Fe oxide , Mn oxide , and Pr oxide , and optionally Ag oxide
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH