Running single point calculations

What do we need?

In order to run LIO, you will need two input files: one containing input options and another one containing the coordinates of the system.

The input coordinates should be provided in an XYZ file format, using atomic numbers to indicate atom identity (i.e. 1 for Hydrogen, 8 for Oxygen, and so forth). For example, a simple oxygen molecule could be provided as:

2

8 0.0 0.0 0.0
8 1.4 0.0 0.0

The first line indicates the number of atoms (although LIO does not need it) and the second line can be used for comments. The options input file should contain a &lio namelist input with the desired options. For example, in the case above of the oxygen molecule:

&lio
 natom  = 2
 charge = 0
 open   = t
 nunp   = 2
 basis_set = '6-31G*'
/

The input file above requests a calculation using the 6-31G* basis set (by default LIO only supports the PBE functional). natom indicates the number of atoms in the system and is mandatory except when using LIO as a QM/MM library. Charge indicates the total charge in the system, while open = t requests an open shell calculation (open = f, or not including it, is closed shell). nunp indicates the number of unpaired electrons, and NOT the multiplicity (nunp = multiplicity -1).

Now that we have our input files, lets call them oxy.in and oxy.xyz, we can simply run LIO as:

liosolo -i oxy.in -c oxy.xyz > outputfile