In the solid state, it exists as the dimer Ga2I6. When vaporized, its forms GaI3 molecules of D3h symmetry where the Ga–I distance is 2.458 Angstroms.
In the solid form, it consists of the dimer Ga2I6. Upon vaporization, it transforms into GaI3 molecules with D3h symmetry, and the Ga–I bond length measures 2.458 Angstroms.