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:

* xyz 0 1
O   0.0000   0.0000   0.0626
H  -0.7920   0.0000  -0.4973
H   0.7920   0.0000  -0.4973


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

./orca water.inp

on a LINUX or MAC terminal or

orca water.inp

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

Save output to a file

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

./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.


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.