Vibrational Frequency

Note

The scripts for this step of the tutorial can be found in chemsh/6_mgo+co2_vib/

The script mgoco2.py demonstrates how the vibrational frequency of CO₂ can be calculated. This is a very similar setup to the MgO-CO₂ geometry optimisation, but starts from the final optimised energy. The active region is also reduced to the CO₂ atoms only, in order to reduce the size of the Hessian matrix required:

# Only CO2 is active for vibrational analysis
print("Active region is: ", co2_atoms)

DL-FIND is used to run the vibrational analysis, which is specified using the thermal=True option in the Opt() specification:

# Run vibrational analysis
opt = Opt(theory=qmmm, thermal=True, active=co2_atoms)
opt.run()