Insights into mechanism of electric field regulating calcium sulfate crystal structure and crystallization: A study by DFT calculation and experiment

Exploring the mechanism of external electric field (EF) regulating the structure and crystallization of calcium sulfate crystal is of great significance for solving the problem of inorganic salt scale in many industrial processes such as desalination and heat exchange. Here, the dispersion-corrected Density Functional Theory (DFT-D) calculations and a series of experiments were carried out to investigate the influence of EF on crystal structure, mechanical property and crystallization of gypsum crystal. The results show that under the influence of EF, the conventional cell of the gypsum crystal shortens in the direction of lattice parameter b. The water layer and the CaO8 octahedron are deformed. The stiffness and hardness of gypsum crystals decreases. The attachment energy and surface energy of (020) plane increase significantly. Both DFT-D calculations and experiment characterization results indicate that EF promotes a regular growth of gypsum crystal mainly along in the direction of (020) plane. Our study results demonstrate the possibility of electrical regulation of calcium sulfate crystal growth to solve the industrial calcium sulfate scale problem.