Dear Rajesh,
If you mean something like LaMnO3+d, the formula should be re-written
La1-dMn1-dO3 since the normal perovskite accepts no interstitial oxygen.
In other cases such as La2CuO4+d the layered strucure allows for
insterstitial oxygen in the LaO layer therefore the formula is correct.
Diff
Rajesh,
Physically speaking, an occupancy of one is generally defined to be a fully
occupied site. So an occupancy greater than one makes no physical sense.
Perovskites *are* sometimes described as oxygen excess though, but when it says
"oxygen excess" it really means "cation deficient". It is
