Table 5. Comparison of the Extrapolated Energy Error (vs CCSDT(Q)) and Confidence Interval for Various Values of τ for CSF-ICEa.
| τ | EICE(6, τ) | EICE∞ | error (mEh) | % NCSFs |
|---|---|---|---|---|
| 7 | –78.207186 | –78.2073(2) | 0.6(2) | 100.0 |
| 6 | –78.207172 | –78.20723(8) | 0.64(8) | 89.1 |
| 5 | –78.207142 | –78.20722(3) | 0.66(3) | 71.1 |
| 4 | –78.207066 | –78.207213(1) | 0.658(1) | 49.0 |
| 3 | –78.206841 | –78.2074498 | 0.450 | 31.8 |
a
A comparison of the CSFs (vs the largest calculation τ = 7, NCSF =3793459) is also given in order to compare the compactness of the wavefunction. The data is for the C2H4 molecule with double-ζ basis and a FCI space of (12e, 36o). The best variational energy EICE(TGen, τ) for each τ is also given for comparison. The τ = 3 extrapolated energy is taken from the three-point formula.