Calculation of Vibrational Frequency of Molecules and Visualization of Normal Modes
Different kinds of calculations require different kinds of input. But some items are to be specified in all the cases. The two most popular computer programs for carrying out ab initio quantum chemical calculations is the "Gaussian" and "Gamess" series.
To study a molecule using these software we need to specify the molecule's Cartesian coordinates or the z-matrix of the molecule or the redundant internal coordinates of the molecule.
We have to also specify the method and also the basis set. For a single point energy calculations the geometry specified by the z-matrix alone is the input.