Using B3LYP calculations on the 6-311G ++ (d, p) group, the structural characteristics and dissociation properties of the chloroethane molecule are discussed from the perspective of molecular structure under an external electric field (0~10.28 V·nm^-1). The calculation results show that with the increase of external electric field, the total energy of the molecule increases, the bond length of the C—C single bond decreases, the bond length of the C—Cl bond increases, the dipole moment increases, the size of the energy gap bond increases and then decreases. At different frequencies, the infrared absorption peaks respectively have red shift and blue shift phenomena, and the intensity of the Raman peaks changes. In addition, with the increase of the external electric field, the dissociation energy gradually decreases, and it can be seen that the potential energy barrier almost no longer exists when the external electric field reaches 18.00 V·nm^-1, representing that the degradation of the chloroethane has been achieved.

Density functional theory was employed to explore adsorption mechanism of benzoic acid and toluene molecules on calcite surface, and to analyze influence of polarity on the adsorption. It showed that benzoic acid was tilted adsorbed on CaCO₃(104) surface in the form of undissociated molecules and in monodentate mode, while toluene was parallel adsorbed. Geometrical structure of organic molecules changed significantly during the adsorption, in which the deformation of benzoic acid was much greater than that of toluene. Meanwhile, electronic structure of the adsorption system was also changed. During the adsorption of benzoic acid, Ca-O ionic bond and H-O covalent bond were formed. However, there was only weak hydrogen bond between toluene and CaCO₃(104) surface. Obviously, adsorption intensity of benzoic acid (polar molecule) on CaCO₃(104) surface is greater than that of toluene (non-polar molecule). It provided theoretical support for EOR and mineral flotation engineering.

We studied adsorption characteristics of oil-water system on calcite and dolomite surface with molecular dynamic simulation. To study wettability of calcite/dolomite surfaces, we analyzed equilibrium conformation, relative concentration, radial distribution function and adsorption energy of calcite/dolomite-oil/water system. Then, we proposed a two-step adsorption mechanism. It shows that dolomite-oil/water system is more easily to achieve thermodynamic stability and is more stable; A water film is formed on calcite and dolomite surfaces, which is a double-layer structure; There are interactions among oil molecules, water molecules and the crystal surface; Attraction of dolomite surface to oil and water molecules is stronger than calcite. Finally, we divided the adsorption process into two steps:Water molecules adsorbed on crystal surfaces form a tightly adsorbed layer under van der Waals forces, electrostatic forces and O(CaCO₃,CaMg(CO₃)₂)-H(H₂O) hydrogen bonds. In addition, the remaining water molecules move to the crystal surface form a diffusion layer under the influence of O(H₂O)-H(H₂O) hydrogen bonds. It reveals wettability formation and alteration mechanisms on calcite and dolomite surface, which paves a foundation of further enhance oil reovery.