We propose to perform neutron diffraction measurements on a honeycomb iridium oxide alpha-Li2IrO3 under pressure. Honeycomb iridates have been intensively studied as a possible materialisation of Kitaev spin liquid, but all of them show a magnetic ordering at low temperatures. We recently found a spin-liquid behaviour in 3D-honeycomb beta-Li2IrO3 under pressure. Moreover, by applying pressure, beta-Li2IrO3 undergoes a structural transition accompanying the Ir-Ir dimerisation. The Ir-Ir dimerisation may be a generic feature in honeycomb iridates under pressure. The 2D honeycomb iridate alpha-Li2IrO3 was also reported to display a structural transition at around 3 GPa. The crystal structure under pressure is, however, yet to be solved, and the possible presence of Ir dimers has not been clarified. We therefore analyse the crystal structure of alpha-Li2IrO3 under pressure at PEARL.