To incorporate GD3 dispersion corrections in Gaussian 16 (G16) when performing calculations using the OPBE functional, you need to set the appropriate environment variable before running your calculation. Specifically, you should set the GAUSS_SCRDIR environment variable to point to the directory where Gaussian will store its scratch files, and then use the EmpiricalDispersion=GD3 keyword in your input file. Here's how you can do it:

export GAUSS_SCRDIR=/path/to/scratch/directory

Replace /path/to/scratch/directory with the actual path where you want Gaussian to store temporary files.

In your Gaussian input file, specify the OPBE functional along with the GD3 dispersion correction:

#P OPBE/6-31G(d) EmpiricalDispersion=GD3

This setup ensures that the GD3 dispersion corrections are included in your calculations with the OPBE functional.

I hope this helps.

To set the environment variable for incorporating the GD3 dispersion in Gaussian 16 (G16) for calculations using the OPBE functional, you need to modify the Gaussian environment file to include the GD3 dispersion. This typically involves setting the `GAUSS_SCRDIR` environment variable to specify the scratch directory and then using the appropriate keywords in your input file. The input file should include `#P OPBE/6-31G(d) GD3` (or the relevant basis set and dispersion correction) in the route section. Ensure Gaussian is properly installed and configured to recognize the GD3 dispersion model.