Different kinds of calculations require different types 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 are the "Gaussian" and "Gamess" series.

To study a molecule using the software, we need to specify the molecule's Cartesian coordinates or the molecule's z-matrix, or the molecule's redundant internal coordinates.

We have also to specify the method and the basis set. For single-point energy calculations, the geometry specified by the z-matrix alone is the input.

The objective of this experiment is to perform geometry optimization using any of the optimization techniques.