Nucleation and Growth of Na<sub>2</sub>CO<sub>3</sub> Clusters in Supercritical Water Using Molecular Dynamics Simulation

Abstract

The nucleation and growth of Na2CO3 particles in supercritical water were investigated using molecular dynamics simulation. The clustering process of Na2CO3 was studied for 1 ns at a series of state points, across temperature and pressure ranges of 700 to 1100 K and 23 to 30 MPa, respectively. The binding energy and radial distribution function analysis showed that the electrostatic interaction was the main factor affecting the whole Na2CO3 nucleation process. Under supercritical conditions, the electrostatic interaction of water molecules with Na + and CO2-3 ions rapidly decreased, allowing Na + and CO2-3 ions to readily collide with each other to form small Na2CO3 clusters. During the initial Na2CO3 nucleation process, all the single-ion collisions were complete within 50 ps and the ionic collision rates appeared to be of the order of 10 30 cm -3 · s -1 . Furthermore, the effect of temperature was found to be more important than that of the pressure at the nucleation stage and a higher temperature led to an enhanced collision rate and the formation of more initial Na2CO3 particles. The further growth of the Na2CO3 particles was more dependent on the pressure.