Structure and properties of uracil and its sulfur analogs: A systematic study of basis set effects inAb InitioSCF calculations

The calculations for uracil and its three sulfur analogs, 2-thiouracil, 4-thiouracil and 2,4-dithiouracil, were carried out using ab initio LCAO-MO method at the Hartree–Fock level. The molecular structure of uracil was fully optimized using standard 3–21G, 6–31G* and 6–31G** basis sets, while geometry optimizations of the thio- and dithio-uracils were performed at the 3–21G* and 6–31G* levels. The basis set effects on structure optimization and one-electron properties are discussed. The geometrical parameters and dipole moments calculated at different levels are compared with the available experimental data.