Hi, I'm sorry, maybe I'm  missing something, but the DFT I used to know refers to electronic structure. What do you mean by 'to do the intermolecular...' - as it looks like you want to solve nuclear motion problem. If you mean rotation barriers, then you simply choose some internal coordinate(s) of interest and perform static DFT calculations for each geometry to get kind of PES for torsional motions.

Regards,

Emil

You should use the reaction coordinate method in which you change an angle in increments and calculate the energy. The DFT calculations are in 25 C. There is no dynamics calculations using DFT. You can use Arrhenius equation  to find the rate or energy barrier at different temperatures.

The answer by Emil is also right.

Thank you all.You are so kind of ypu