Beginner--Help on using FindRoot to solve the system of equations

*To*: mathgroup at smc.vnet.net*Subject*: [mg66190] Beginner--Help on using FindRoot to solve the system of equations*From*: xiaochu at che.utexas.edu*Date*: Wed, 3 May 2006 02:45:50 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

This is a code to solve vapor-liquid equilibrium by van der Waals Equation of State. I don't why this code is not working, please help, thanks very much! (* Name of EOS *) EOSName = "Van der Waals"; Ttilde = .; Dtilde = .; Z = 3/(3-Dtilde)-9*Dtilde/8/Ttilde; (* Related variables *) Psi1 = (-9*Dtilde)/(8*Ttilde) - Log[3-Dtilde]; lnB = (1-Z)-Psi1; mu = -lnB+Log[Dtilde]; P = Dr Ttilde Z; DtildeG=10^-14; DtildeL=2.91; Dtilde1=.; Dtilde2=.; mu1=mu/.Dtilde->Dtilde1; mu2=mu/.Dtilde->Dtilde2; P1=P/.Dtilde->Dtilde1; P2=P/.Dtilde->Dtilde2; Ttilde = 0.1; Result= FindRoot[ {P1==P2,mu1==mu2}, {Dtilde1,DtildeG}, {Dtilde2,DtildeL}, MaxIterations->1000, WorkingPrecision->16]; Link to the forum page for this post: http://www.mathematica-users.org/webMathematica/wiki/wiki.jsp?pageName=Special:Forum_ViewTopic&pid=10101#p10101 Posted through http://www.mathematica-users.org [[postId=10101]]