# Minimal input¶

Most keys in the input file for ADF are optional. Default values are used for omitted keys. Assuming the default values are sensible, short input files can often be used. We will examine first the minimal input that is required to run ADF. Having read that part, you can start to do calculations.

The following input will run a geometry optimization on water, using a (almost) minimal input:

ATOMS
O  0  0  0
H  1  1  0
H -1  1  0
End

Basis
End

Geometry
End


This is the input for the ADF program. You need to store it in a file, and pass it as standard input to ADF.

For example, assume you have stored the above input in a file in. Also assume that the $ADFBIN directory is in your$PATH. Then you run ADF using the following command:

adf <in >out

ADF will run, and the resulting output will be stored in the file out. If you examine the contents of this file, you will find that ADF has actually run three times: two create runs, and one geometry optimization. The fragment files produced by the create runs are saved in t21.H and t21.O, for hydrogen and oxygen respectively.

## Shell script¶

Like in the Examples, one can put the call to adf inside a shell script, for example, the content of the file ‘example.run’ could be like:

#! /bin/sh

ATOMS
O  0  0  0
H  1  1  0
H -1  1  0
End
Basis
End
Geometry
End
eor


The shell script ‘example.run’ needs be executable, if it isn’t you will need to make it executable, e.g. chmod u+x example.run. The ‘example.run’ file needs to be executed as a shell script, not as input to ADF.

./example.run >example.out