# Calculation of dispersion energy in Gaussian 09

How can I calculate the dispersion energy using Gaussian 09? Where is it printed in the output file when using wb97xd/cc-pvdz sp? If it isn't printed by default, what flags can be used to turn printing on?

• Depending on the functional you use, it either contains some dispersion correction or not. For those which do not you can manually add it with EmpiricalDispersion=... if it is parameterized. If not, you can specify the parameters via the command line. See the manual for detail. The omegaB97XD DFA already contains the dispersion; it is parametrized that way. You will not be able to find a value for the dispersion correction. – Martin - マーチン Dec 22 '16 at 11:49

The value of the empirical dispersion correction is printed when the print level is turned up using #p in the route line. For any method that contains an empirical dispersion correction, search for R6Disp or Dispersion energy, where other parts of the line will vary depending on the type of correction (-D2, -D3, or -D3(BJ)):
R6Disp:  Grimme-D2 Dispersion energy=       -0.0174233223 Hartrees.

This line is not printed with # or #n at the start of the route section.