The self-assembly of Ca 2+ and CO 2− 3 ions into nanoparticles in water and hydrophobic solvents is investigated using Molecular Dynamics (MD) computer simulation. A new three-stage particle assembly procedure is used which relaxes the structure of the nanoparticle towards a lower energy state. In hydrophobic solvent the bare particle is essentially spherical whereas in water it is ellipsoidally shaped. With surfactant stabilizer the nanoparticles typically exhibit non-spherical cores in model hydrophobic solvents. Binary surfactant systems exhibit synergistic effects were for example a salicylate-sulfonate combination forms a cage which promotes a compact core. Synergistic effects on the shape of the particle were also observed in a hydrophobic solvent for surfactant-stabilized systems with trace water as a third component.The simulations show that rather than being a rigid structure the carbonate core shape and stabilizing shell coverage is sensitive to solvent, surfactant and small polar molecules which act as co-surfactants.