How to optimize a large molecule?

[Jerry Leung]

I have designed a new molecule which contains totally 7 benzenes and 2 oxygen atoms.Then I tried to optimize its geometric structure on VNL but I failed many times.I wonder how large should my molecule be may it be optimized successfully on VNL?
Thanks for your answering.

[Nordland]

There is no size limit on the structure you want to optimize - however there could be two problems at the top of my head. First of all there could be something wrong with the initial setup or alternative your method could be insufficient for this molecule.

Nevertheless we will not get closer to the solution unless you share a bit more information.

[Jerry Leung]

I sincerely thank for your answer.I have found out the crux of  my problem just after I posted the note this morning:When I created my molecule ,I forgot to fuse one of  superpositioning atom!When the calculation began,it always reminded me of my probable problem,but I couldn't really understood what it meant.Maybe the next time I should also posted the warning VNL gave me on the forum.
Thank you very much,Nordland.