A "semi-classical" method was developed for molecular dynamics simulation of a system with ionic-covalent bonds like silica. The ionic charges were calculated by minimization of the potential energy on each step of molecular dynamics simulation. Ionic-covalent potential was used in modeling of SiO2 molecule, non-crystalline silica, and calcium metasilicate. The internal energy of a system includes energies of silicon ionization, affinity of oxygen to electrons, Coulomb interactions and repulsion of ions, and covalent Si-O energy. Calculated properties of glassy and liquid silica and SiO2 molecule, such as density, internal energy, compressibility, distances between ions and vibration frequencies, are close to experimental values. Published by Elsevier Science B.V.