Formic acid tetramers: a structural study

Hybrid density functional calculations are used to locate 75 local minima on the potential energy surface of the formic acid tetramer. Additional computations are performed for the 33 lowest-energy structures with larger basis sets. The global minimum is a planar structure consisting of a pair of lowest-energy dimers bound to each other by C–H⋯OC bonds. The lowest-energy cyclic structure has one of the monomers in the E conformation.