I didn't know how to find a solution fminsearch

Hello,

I will be happy if someone help me to solve this problem, because I work on it for 4 days but I didn't find the solution

I want to minimize this equation with fminsearch :

I took the following steps :

% g(E):
function [DOS_Gauss] = DOS_Gauss(sigma,N,E,E_LUMO)
DOS_Gauss=N./(sigma*sqrt(2*pi)).*exp(-(E-E_LUMO).^2./(2*sigma^2));
end

% 1-f(E,E_f):
function [C_D_Fermi]=C_D_Fermi(D_Fermi)
C_D_Fermi=1-D_Fermi;
end

% [1-f(E,E_f)]*g(E):
function [n_t_1]=n_t_1(DOS_Gauss,C_D_Fermi)
n_t_1=C_D_Fermi.*DOS_Gauss;
end

% ?[1-f(E,Ef)]g(E)dE:
function [n_t_f_1]=n_t_f_1(n_t_1,E1)
n_t_f_1=trapz(E1,n_t_1);
end

% 1-f(Et-Ef):
function [C_1_D_Fermi] = C_1_D_Fermi(E_t,E_f,K_B,T)
C_1_D_Fermi = 1-(1./(1+exp((E_t-E_f)./(K_B*T))));
end

%g(Et):
function [C_DOS_Gauss] = C_DOS_Gauss(sigma,N,E_t,E_LUMO)
C_DOS_Gauss=N./(sigma*sqrt(2*pi)).*exp(-(E_t-E_LUMO).^2./(2*sigma^2));
end

% [1-f(E_t,E_f)]*g(Et):
function [n_t_2]=n_t_2(C_DOS_Gauss,C_1_D_Fermi)
n_t_2=C_1_D_Fermi.*C_DOS_Gauss;
end

% TE:
function [E_T]=f_min(Bc,K_B,T,Alpha,n_t_f_1,n_t_2)
E_T=abs((2/3)*(4.*pi/3*Bc).^-1/3.*(K_B*T./Alpha).*(n_t_f_1).^-4/3.*n_t_2-1);
end
E_t_0=0.0;
E_t=fminsearch(@f_min,E_t_0,[],Bc,K_B,T,Alpha) 

I Have here the problem, with my variable is " E_t"

Help me please.

Best regard,

[John D'Errico]

Terribly hard to dig through. You have this confusing bundle of functions for no good reason. That is, if you just want to subtract 1 from something, you don't need to make a separate function out of it.

First problem:

function [C_DOS_Gauss] = C_DOS_Gauss(sigma,N,E_t,E_LUMO)
    C_DOS_Gauss=N./(sigma*sqrt(2*pi)).*exp(-(E_t-E_LUMO).^2./(2*sigma^2));
end

Making the output variable of a function to have the same name as the function is sure to cause problems. I'm not sure if it actually causes an error, but it will certianly cause you pain if you ever need to debug your code in the future.

A big problem of your code is this:

function [n_t_2]=n_t_2(C_DOS_Gauss,C_1_D_Fermi)
    n_t_2=C_1_D_Fermi.*C_DOS_Gauss;
end

These are functions themselves: C_DOS_Gauss and C_1_D_Fermi. But now you want to form the product of the result of them. However, you cannot just multiply the names of those functions. They have inputs.

[John D'Errico]

That you have worked on it for 4 days does not mean you should post the same question every day for 4 days in a row. Stop the duplicate posts. I've now seen at least 3 of them. One you got answers on. This one hs gotten nothing more than a comment by me. And the other I closed.