Hello water! Your first ORCA calculation
========================================

Our first calculation will be the energy of a water molecule, using Hartree-Fock theory and the DEF2-SVP basis. All you need to run ORCA is an input text file, such as this water.inp::

   !HF DEF2-SVP
   * xyz 0 1
   O   0.0000   0.0000   0.0626
   H  -0.7920   0.0000  -0.4973
   H   0.7920   0.0000  -0.4973
   *
   
.. note::
   The input usually has the .inp extension, but .txt is also ok.
   
You can start by putting this as a file in the ORCA folder and, from there, running

.. prompt:: bash $

   ./orca water.inp
   
on a LINUX or MAC terminal or 

.. prompt:: bash

   orca water.inp
   
on the Windows prompt (click windows key, type "prompt" to find it). 

.. _output_to_file:

Save output to a file
.....................

The output is then printed on the screen. If want to save to a text file, just use instead

.. prompt:: bash $

   ./orca water.inp > water.out
   
to redirect the printing to the water.out file. You can then open the file while the calculation is running to follow it. More on the input and output analysis `next`_.

.. note::
   You don't need to worry about the other programs on the folder for now, ORCA will take care of calling the right one when needed.

.. _`next`: input_output.html