Accurate atomization energies and heats of formation of the main isomers of disilyne molecule (Si2H2) have been determined on the basis of coupled-cluster-theory calculations with a family of Dunning's correlation-consistent basis sets using complete-basis-set extrapolations. The zero-point energy, core/valence, Douglas-Kroll-Hess relativistic, higher order and atomic spin-orbit corrections have been also taken into account. Based on the recommended value of the standard heat of formation of atomic silicon in the gas phase (108.2 kcal/ mol), the following standard gas-phase heats of formation of Si2H2 isomers have been obtained: 97.2 kcal/ mol for the dibridged C-2 nu, 106.8 kcal/ mol for the monobridged C-s, 110.2 kcal/ mol for the vinylidene C-2 nu and 115.5 kcal/mol for the trans C-2h. (c) 2008 Elsevier B. V. All rights reserved.