Table 2. Optimal VMC Ground- and Excited-State Bond Lengths (Å) and Angles (deg) of Thiophene Using “cmax × SA” CIPSI Expansions and the maug-cc-pVDZ Basis Set.
| state | δEPT2 | no. det | no. param | C–C | C=C | C–S | δCCCS |
|---|---|---|---|---|---|---|---|
| GS | –0.67 | 1037 | 2002 | 1.4281(2) | 1.3662(1) | 1.7201(2) | 0.06(5) |
| –0.64 | 2614 | 2823 | 1.4282(2) | 1.3681(2) | 1.7202(1) | 0.09(3) | |
| –0.59 | 5605 | 4106 | 1.4290(2) | 1.3669(1) | 1.7218(1) | -0.08(3) | |
| –0.54 | 11003 | 6326 | 1.4279(4) | 1.3676(4) | 1.7223(4) | 0.05(4) | |
| CASPT2a | 1.430 | 1.372 | 1.720 | 0.00 | |||
| CCSD(T) (BFD)b | 1.425 | 1.368 | 1.717 | 0.00 | |||
| CCSD(T) (FC)b | 1.430 | 1.372 | 1.728 | 0.00 | |||
| CC3 (FC)b | 1.430 | 1.372 | 1.729 | 0.00 | |||
| ES | –0.67 | 1663 | 3630 | 1.4396(7) | 1.4161(6) | 1.7626(5) | 24.84(2) |
| –0.63 | 3752 | 4957 | 1.4388(7) | 1.4151(3) | 1.7655(4) | 25.58(3) | |
| –0.59 | 8304 | 7271 | 1.4383(1) | 1.4144(2) | 1.7709(1) | 25.75(2) | |
| –0.546 | 15815 | 10278 | 1.4422(7) | 1.4112(4) | 1.7725(6) | 26.01(7) | |
| CASPT2a | 1.448 | 1.423/1.416 | 1.782/1.778 | 26.7 | |||
| ADC(2)c | 1.422 | 1.419 | 1.796 | 28.2 | |||
| DFT/MRCId | 1.436 | 1.394 | 1.799 | 27.4 | |||