Molecular dynamics simulations on K₂SO₄ nucleation in supercritical water

K₂SO₄ nucleation in supercritical water was investigated by molecular dynamics simulation. The clustering process of K₂SO₄ was studied for 1 ns in the temperature range of 573–1073 K and in the pressure range of 22–28 MPa. Binding energies, radial distribution functions, and hydrogen bond network analyses showed that temperature and density played significant roles in the nucleation process. With temperature increasing, electrostatic interactions among water molecules and hydrated K⁺ and SO₄²⁻ were weakened, so resulting in the reduction of binding energies. Hydrogen bond network was destroyed under supercritical conditions. In addition, high temperature improved the diffusion coefficient of ions. K⁺ and SO₄²⁻ could break through the electrostatic shielding effect of water molecules and tended to collide with each other to form ion pairs. The collision of small clusters or ion pairs further produced larger clusters. Moreover, high temperature and low density contributed to the formation of dispersed small clusters.