Which isomeric form of formaldehyde dimer is the most stable - a high-level coupled-cluster study

- CCSD(T) computations have been employed to obtain accurate characteristics of (H2CO)2.
- Both dimers exhibit CO bond elongation and C-H bond shrinking compared to H2CO.
- Dimer I has been found to be the global-minimum structure.
- Dimer II lies 0.3-0.4 kcal/mol higher in energy than dimer I at 0 K.