inverse iteration in region 1,2 and 5: p = g(d,T)
function pofdt125 extends Modelica.Icons.Function; input SI.Density d "density"; input SI.Temperature T "temperature (K)"; input SI.Pressure reldd "relative iteration accuracy of density"; input Integer region "region in IAPWS/IF97 in which inverse should be calculated"; output SI.Pressure p "pressure"; output Integer error "error flag: iteration failed if different from 0"; end pofdt125;