A large number of potential phase-change materials have been have produced promising results experimentally; however, only Ge2Sb2Te5-based PCMs have been significantly explored so far using ab initio molecular-dynamics (AIMD) simulations. We present the first AIMD study of the full melt/quench/anneal cycle for Ga -Sb PC materials, for compositions ranging from the near-eutectic alloy Ga16Sb84, to stoichiometric GaSb. The primary changes in local environment associated with crystallisation are demonstrated, and correlated with increasing Ga content. For Ga16Sb84, it is shown that crystallisation is characterised by the transition of Ga atoms from a tetrahedral to octahedral-like coordination. In GaSb, the opposite transition occurs for Sb atoms, from octahedral-like to tetrahedral coordination. The electronic density of states and the optical reflectivity are calculated for each phase and demonstrate good agreement with experimental results.