MRCI investigation of different isomers of Ni2O2H2+

Abstract

The geometrical and electronic structures of different isomers of Ni₂O₂H₂⁺ are investigated by multireference configuration interaction (MRCI) calculations using natural atomic orbital basis sets. The lowest-lying isomer, Ni₂(OH)₂⁺, has a rhombic shape with two OH groups bridging the Ni atoms. The next isomer in energetic order with a relative energy of 0.29 eV consists of a linear NiONi(OH₂)⁺ chain. Other structures with a rhombic shape, (NiH)₂O₂⁺, with H bound to the Ni atoms have considerably higher energies, above 4 eV. Especially the low-lying isomers are characterised by a large number of low-lying electronic terms. The product Ni₂O₂H₂⁺ of the reaction of Ni₂O₂⁺ with small alkanes is likely to have the rhombic Ni₂(OH)₂⁺ structure. The reaction energy of the reaction Ni₂O₂⁺ + H₂ → Ni₂(OH)₂⁺ is estimated to be about −3.5 eV.