Total energy convergence

The total energy in ab initio theory is given relative to the separated particles, i.e. bare nuclei and electrons. The experimental value for an atom is the sum of all the ionization potentials for a molecule there are in addition contributions from the molecular bonds and associated zero point energies. The experimental value for the total energy of FI2O is -76.480 au and the estimated contribution from relativistic effects is -0.045 au. Including also a mass correction of 0.0028 au (a non-Born-Oppenheimer effect that accounts for the difference between finite and infinite nuclear masses) allows the experimental non-relativistic energy to be estimated as -76.438 0.003 au.  

For the cc-pVDZ basis set, the full Cl result is available, which allows an assessment of the performance of various approximate methods. The percent of the electron correlation recovered by different methods is shown in Table 11.7. 

The calculated total energy as a function of basis set and electron correlation (valence electrons only) at the experimental geometry is given in Table 11.8. As the 

Method cc-pVDZ cc-pVTZ cc-pVQZ cc-pV5Z cc-pV6Z CC-pVooZ 

The magnitude of the core correlation can be evaluated by including the oxygen Is-electrons and using the cc-pCVXZ basis sets, with the results shown in Table 11.9. 

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Valence Bond Methods j 11.2 Total Energy Convergence 267 ... 

Total Energy Convergence Dipole Moment Convergence... 

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