trouble with energy minimization

Hi All

I imported the AL2O3 srtucture from metal oxide part; then I wanted to minimize energy of AL2O3 srtucture, but I got problem. The occured error is "Error energy expression: cannot find parameters for bond : O(o-al)-AL(al3o)"

I appreciate you if you help me.

The structure has been attached to this post.

Thanks in advance!

nima