error loop related to code not converging

function[Ps,T,Vl,Vv]= Ps_VDW_Plot(Pc,Tc,Pso,Tmin,dT)
%this is a function that calculates and plot the vapour pressure and the
%specific molar volume V for a pure fluid at given temperature T using both
%VDW-CEOS and considering a minimum value of temperature Tmin(loaded  by user this requires
% where DT is stepwise increase in Temperature
%Ps_VDW as a subprogram to run. all parameters in SI units i.e
%P(Pa),T(K),V(m3/mol)

%initializing the iteration process
i=1;

%initial input temperature
T(i)=Tmin;

%calculation of Ps using Ps_VDW function

[Ps(i),Vl(i),Vv(i)]= Ps_VDW(Pc, Tc, Pso, T(i));
while Vl~=Vv
    i=i+1;
    T(i)=T(i-1)+dT;
    [Ps(i),Vl(i),Vv(i)]= Ps_VDW(Pc, Tc, Ps(i-1), T(i));
end

%plot of P vs. T
    plot(T,Ps);
end

please am having difficulty getting a fixed result/plot from this function 
given that 
Pc=4.8e6;
Tc=508.1;
Tmin=300;
dt=0.5;
Pso=100;

please run the file with the details below and tell me why it doesnt give consistent results