//Peng-Robinson ̼㣺

m=0.37464+1.54226 - 0.26992^2;
=1+m[1-(T/Tc)^0.5];
a=0.45724[(RTc)^2/Pc];
b=0.07780(RTc)/Pc;
P=R*T/V-a/[V(V+b)+b(V-b)];

