Dmol3 optimization

Dear all,

I was using Dmol3 to optimize a crystal structure (CoAl2P3O12). It looks strange to me that the energy did not always go down. It went up and down periodically. Can anyone tell me what was going on?

Energies:

t3-o11 Energies.JPG

Convergence:

t3-o11 Convergence.JPG

Many thanks,

Yi