Influence of the computation conditions on the results in density functional calculations

The influence of the computation conditions on the results in the calculati ons with Kohn-Sham density functional theory has been studied through a ser ies of calculations on the molecules with various compositions and structur es such as BCl3, SO2, ZnO, TiCl4, LuF3. Three factors are considered. It is found that the completeness of the basis sets is the most important factor . The number of the grid points of the numerical integration is less import ant. The projection for decomposing the molecular charge into multipolar co mponents centered in each atomic nucleus converges fairly rapidly. The mole cular geometry and the fundamental vibrational frequency are insensitive to the computation conditions, while the total energy and bond energy are pre tty sensitive. If the same basis set and the same numerical integration poi nts are used for a molecule and its constituting atoms in calculating its b ond energy, the error of the calculated result could be reduced. It is show n that the calculation results with an accuracy matched with the approximat e DFT formulas can be obtained by choosing the mediate computation conditio ns with a smaller computational effort.