Table 1. Summary of the Various Approximations Used to Speed up Explicitly Correlated CCSD(T) Calculations.
| Approximation | Truncated basis | SVDa | Applicationb |
|---|---|---|---|
| FNO | virtual HF MO (a) | tijab[1] | F12, CC |
| NAF | DF auxiliary (P) | Jp′q,P | F12 |
| Jpq,P | CC | ||
| NAB | complementary MO (a′) | Ja′p,P | F12 |
a
The quantity the SVD of which is used to construct the truncated basis.
b
The approximation is applied to reduce the corresponding dimension of F12-dependent intermediates (F12) or integrals, intermediates, and cluster amplitudes entering the CCSD(T) equations (CC).