The Gibbs energy, defined as G = U + P V -T S, is the single thermodynamic function that captures all thermodynamic effects of temperature and pressure for systems that are at maintained constant pressure and temperature. The total internal energy, U , captures the total molecular potential energy and kinetic energy of the system, molar volume V directly quantifies the space occupied by the system at a given external pressure and temperature condition, and S, the molar entropy, is the measure of the distribution of accessible thermodynamic states both in terms of configuration and energy of the system at a given temperature and pressure.