A semi-ionic model is proposed for simulations of bulk metal oxides and interfaces between metal oxides and organic molecules. In this model, the electrostatic interactions are represented by partial charges on atoms; the covalent contributions are represented by a Morse function, and the van der Waals interactions are represented by a Lennard-Jones (LJ) function. Four potential functions are parametrized, using experimental data of representative binary oxides, by combining the Morse and electrostatic terms with LJ-12-6, LJ-9-6, and polarization shell model. The resulting potential functions are validated by predicting bulk properties of binary and ternary oxides. Coupled with classical force field parameters for organic molecules, one of the potentials is applied to study the adsorption energies, structures, and isothermal curves of methanol molecules on a MgO (100) surface.