# Quick Start Guide

Gibbs2 reads the user commands from a single input file (the .ing file). A simple input (mgo.ing) is:

NAT 2
MM 40.3044
PHASE mgo
81.8883583665837   -73.5171659350000
90.1833999559730   -73.5508544000000
98.4784415453624   -73.5712754950000
106.7734831347517   -73.5826963000000
115.0685247241411   -73.5878968050000
123.3635663135304   -73.5887555350000
131.6586079029198   -73.5865593900000
139.9536494923091   -73.5822069800000
148.2486910816984   -73.5763274850000
156.5437326710878   -73.5693791200000
160.0000000000000   -73.5662512150000
ENDPHASE


This input gives the data for a simple calculation of the thermodynamic properties in MgO. The keywords are:

• NAT: the number of atoms in the system. Typically, this value is the number of atoms per formula unit but it can also be per unit cell, per molecule, etc. All extensive quantities in output are given per NAT atoms.

• MM: the molar mass per NAT atoms.

• PHASE: the definition of a new phase. In this case, the rocksalt-type phase of MgO. A number of lines follow containing pairs of volume/energy data (in bohr^3 and Hartree). The volume and energy correspond to NAT atoms. The input of data for this phase ends with the keyword ENDPHASE.

To run an input, do:

gibbs2 mgo.ing


This will write to the standard output. Redirect the output to a file with either of:

gibbs2 mgo.ing > mgo.outg
gibbs2 mgo.ing mgo.outg


In addition to the output, gibbs2 generates a number of auxiliary files (plots, tables, etc.). The output files typically have the same root (that is, the name up to the last .) as the input file.

Gibbs2 accepts many keywords and commands. For a full description, see the manual. A summary of all available keywords can be found in the syntax page. Some examples can be found in the list of tests.