MATLAB: “Index in position 1 exceeds array bounds (must not exceed 1).” Error

activity coefficientsarraychemistryerrorindexindexingthermodynamic

Hi
I've been given a program that calculates the activity coefficients gamma) and the activity of each component in a mixture. Except i can't run it without getting this error:
Error in TestingSubprograms (line 18)
[gamma,a]=ACTIVITY_WILSON(MW,rhoL,BIP,T,x)
The function is:
function [gamma,a]=ACTIVITY_WILSON(MW,rhoL,BIP,T,x)
%This program calculates the activity coefficients (gamma) and the
%activities (a) of each component of a mixture of c components using the
%Wilson model.
%INPUT PARAMETERS: MW: vector (1xc) reporting the molecular weights of the
%c components; rhoL, vector (1xc) reporting the liquid density of the c
%pure components at temperature T; BIP is a matrix cxc reporting the energy
%interaction parameters (BIP(i,j)=lambda_ij-lambda_ii, J/mol). The energy
%interaction parameters are temperature independent; T: temperature of the
%system; x vector (1xc) reporting the mole fractions of the components of
%the mixture.
%OUTPUT PARAMETERS: gamma: vector 1xc reporting the activity
%coefficients of the components of the mixture; a: vector 1xc reporting the
%activities of the components of the mixture.
%Unless otherwise stated, all input/output parameters are expressed
%according to MKS.
R=8.314;
c=length(x);
%Molar volumes of the pure liquid components composing the mixture
VL=1./((rhoL*1000)./MW);
%Lambda terms (dimensionless) of the Wilson formula
for i=1:c
for j=1:c
Lambda(i,j)=(VL(j)/VL(i))*exp(-BIP(i,j)/(R*T));
end
end
for i=1:c
for j=1:c
A=sum(x.*Lambda(j,:));
C(j)=x(j)*Lambda(j,i)/A;
end
lngamma(i)=1-log(sum(x.*Lambda(i,:)))-sum(C);
gamma(i)=exp(lngamma(i));
a(i)=gamma(i)*x(i);
end
end
The input i'm using is :
x=[0.1 0.9];
MW=[60.09 100.16];
rhoL=[803 802];
T=303.15;
BIP=[196.250 386.133];
Any help would be appreciated. Thanks

Best Answer

  • Problem is with your BIP. It shoule be cXc matrix i.e it shoule be 2X2 for your inputs. You have entered it as 1X2, so the error.
    BIP=[196.250 386.133;196.250 386.133];
    Or change these lines:
    for i=1:c
    for j=1:c
    Lambda(i,j)=(VL(j)/VL(i))*exp(-BIP(i,j)/(R*T));
    end
    end
    to
    for i=1:c
    for j=1:c
    Lambda(i,j)=(VL(j)/VL(i))*exp(-BIP(j)/(R*T));
    end
    end