[Wien] stability issue

[chin Sabsu]

Dear Sir,
I am working on the system ABO3 . 
I have calculated formation energy in two ways: 

Delta_E= Et[ABO3]  - Et[AO]  - Et[BO2]  ------ (1)

 Delta_E= Et[ABO3] - Et[A] - Et[B] - 3/2Et[O2]    ----- (2)
The Delta_E is positive 0.04 Ry from Eq (1) while is negative from Eq 2.  
Why is the energy difference calculated from Eq (1)   positive?

Thanks in advance!

Regards
Chin
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