Thank you for your prompt reply, but my point is, when I optimize a structure of the atom I used to go to other places, and change to another structure which are not I need. For example: the structure in appeend file of origin2.gif is my need ,but no matter how do I change the position of the hydrogen atom, it always run to the carbon atoms on the edge of the opposite, and change to the structure in appeend file of optimized2.gif.
And I met the same thing many times,as the other example as the append files.