Different properties of the molecular structures of favipiravir and ribavirin, which are used in the treatment of SARS-CoV-2 and also needed in the treatment of coronavirus disease (COVID-19) in recent years, have been investigated using Density Functional Theory (DFT) B3LYP/6-311G(d, p) and 6-311+G(d, p) methods. The geometrical optimization of the molecular structures of favipiravir and ribavirin was made in the ground state, gas, and water solvent...