Gibbs function for region 1, 2 or 5: g(p,T,region)
function gibbs import ThermoSysPro; extends Modelica.Icons.Function; input Units.SI.Pressure p "pressure"; input Units.SI.Temperature T "temperature (K)"; input Integer region "IF97 region, 1, 2 or 5"; output Real g "dimensionless Gibbs funcion"; end gibbs;