Dimers between the hydrides LiH, BeH2, BH3, CH4, NH3, H2O and HF

CCSD(T)/aug-cc-pVQZ calculations were performed on dimers of second-row hydrides. The hydrides can be divided into two groups, group X with LiH, BeH2, BH3, and group Y with CH4, NH3, H2O and HF. Dimers within group X are cyclic, dimers within group Y are hydrogen-bonded, and dimers of group X with group Y hydrides are main group-bonded. Cyclic dimers have the highest dissociation energies, from 11,847cm(-1) for BeH2-BeH2 (with structure HBe-H-2-BeH) up to 23,336 cm(-1) for LiH-BH3 (with structure Li-H-3-BH). Main group-bonded dimers have intermediate dissociation energies, the highest being 10,942 cm(-1) for BH3-NH3 with B-N bonding, whereas hydrogen-bonded dimers have lower dissociation energies, the largest being 4302 cm(-1) for NH3-HF with N-H bonding. Stable dihydrogen-bonded dimers were found for LiH-CH4 and BeH2-HF. Harmonic vibrational frequencies and infrared intensities of the BH3-NH3 dimer are compared with corresponding monomer values. Vibrational properties of the cyclic LiH-BH3 dimer are related to those of the BH4 anion.