5 How to prepare an input file

As explained in the introduction, the input file should contain the following minimum information.

• Geometry specification.
• Specification of one-electron basis set (although there is a default).
• Specification of the method to compute the many-electron wavefunction. Several calculations of different type can follow each other.

We will consider these three in turn.

All input can be given in upper or lower case and in free format. Most input lines start with a keyword, which is followed by numbers or other specifications. The different entries on each line should be separated by commas (see next section for more explanation about this).