关于三元热力学体系方程双节线的matlab流程代码

求大家看下代码哪里有问题

%a为稀相,b为浓相
V_1=18.07;
V_2=73.13;
V_3=107894.7;

u_1a=phi_1a/(phi1_a+phi2_a);
u_1b=phi_1b/(phi_1b+phi_2b);
u_2b=phi_2b/(phi1_b+phi2_b);
u_2a=phi_2a/(phi1_a+phi2_a);

g_12a=-1.302+1.08/(1+0.860u_2a);
g_12b=-1.302+1.08/(1+0.860
u_2b);
g_13a=-((log(1-phi_3a))+phi_3a)/(phi_3a)^2;
g_13b=-((log(1-phi_3b))+phi_3b)/(phi_3b)^2;
g_23=0.5-3.31.184^2V_2;

phi_1a=n_1aV_1a/(n_1aV_1a+n_2aV_2a+n_3aV_3a);
phi_2a=n_2aV_2a/(n_1aV_1a+n_2aV_2a+n_3aV_3a);
phi_3a=n_3aV_3a/(n_1aV_1a+n_2aV_2a+n_3aV_3a);

G=n_1log(phi_1)+n_2log(phi_2)+n_3log(phi_3)+g_12n_1*(phi_2)+g_13n_1(phi_3)+g_23n_2(phi_3);

Gphi_1a=diff(G,n_1a,1);
Gphi_1b=diff(G,n_1b,1);
Gphi_2a=diff(G,n_2a,1);
Gphi_2b=diff(G,n_2b,1);
Gphi_3a=diff(G,n_3a,1);
Gphi_3b=diff(G,n_3b,1);

for phi_3a=10^-3:1
V_1=18.07;
V_2=73.13;
V_3=107894.7;

     phi_1a+phi_2a+phi_3a==1;
     phi_1b+phi_2b+phi_3b==1;
     Gphi_1a=Gphi_1b;
     Gphi_2a=Gphi_2b;
     Gphi_3a=Gphi_3b; 
     if phi_3b<=phi_3a
         phi_3a=phi_3a-(10^-3);
     end

end

无法从 sym 转换为 logical。

出错 shuangjiexian1 (第 43 行)
if phi_3b<=phi_3a

Caught "std::exception" Exception message is:
Invalid character code sequence detected.

给phi1a phi2a phi3a赋初始值,然后随着10负8次方递减或递加,然后满足那几个方程最后结果phi3a小于phi3b就输出
输出符合方程的对应的各phi_1a,phi_1b,phi_2a,phi_2b,phi_3a,phi_3b的值