the file has been generated using the reaction preview option, I specified the reactant and the product in separate 3D atomistic documents (.xsd), then I got a trajectory file (which can be animated to monitor the reaction from reactant to product).
Actually, as I explained above I already have the product (as 3D atomistic document) and I can run the geometry optimization on it, however, I'm wondering if I use the generated trajectory file would give more realistic results, as my final objective is not limited to geometry optimization, but rather I want to calculate the thermodynamic properties.