Table 4. Zero-Point Energy Difference (ΔZPE) of the Most Relevant Vibrational Modesa.
| HCOOH | HCOOD | DCOOH | DCOOD | |
|---|---|---|---|---|
| ΔZPE(ν(O–H(D)))/meV | 40.4 | 31.1 | 40.2 | 31.2 |
| ΔZPE(ν(C–H(D)))/meV | –3.9 | –3.3 | –0.6 | –0.5 |
| ΔZPE(ν(C–O))/meV | –10.4 | –2.8 | –7.4 | –2.2 |
| ΔZPE(δ(H(D)′O′C))/meV | 5.2 | 2.0 | 3.8 | 2.3 |
| ΔZPEH(D)COOH(D) – ΔZPEHCOOH (selected modes)/meV | 0.0 | –4.3 | 4.7 | –0.5 |
| ΔZPEH(D)COOH(D) – ΔZPEHCOOH (all modes)/meV | 0.0 | –4.0 | 4.3 | 0.6 |
a
ν denotes a stretching and δ denotes a liberation mode. We do not list the vibrational modes with ΔZPE between the isotopologues of <1.3 meV. The last two rows show the ΔZPE between a particular isotopologue and HCOOH caused by the selected vibrational modes and all vibrational modes, respectively. The frequencies for the adsorbed molecule are calculated using DFT PBE-TS.