  We performed a benchmark study on a series of dihydrogen bond complexes and
constructed a set of reference bond distances and interaction energies. The
test set was employed to assess the performance of several wave-function
correlated and density functional theory methods. We found that second-order
correlation methods describe relatively well the dihydrogen complexes. However,
for high accuracy inclusion of triple contributions is important. On the other
hand, none of the considered density functional methods can simultaneously
yield accurate bond lengths and interaction energies. However, we found that
improved results can be obtained by the inclusion of non-local exchange
contributions.
