[Sowmiya]

Hi all,
i include 5 species in my reaction and i want to determine the multicomponent diffusion through UDF. Dij was calculated as shown

DEFINE_DIFFUSIVITY(diffusion_coef_crct,c,t,i)
{
Material *spi;
Material *spj;

int j;
real mmass_i,mmass_j,ttemp,Pressure=1e+05,aux=0.0,aux1= 0.0,aux2=0.0,aux3=0.0,spe_name;
ttemp=C_T(c,t);

{
mixture_species_loop(THREAD_MATERIAL(t),spi,i)
{
mixture_species_loop(THREAD_MATERIAL(t),spj,j)
{
if(i==0 && j==1) aux1 = collin_NplusN(ttemp);
else if(i==0 && j==2) aux1 =collin_NplusN2plus(ttemp);
else if(i==0 && j==3) aux1 =collin_NplusE(ttemp);
else if(i==0 && j==4) aux1 =collin_NplusN2(ttemp);
else if(i==1 && j==2) aux1 =collin_NN2plus(ttemp);
else if(i==1 && j==3) aux1 =collin_Ne(ttemp);
else if(i==1 && j==4) aux1 =collin_NN2(ttemp);
else if(i==2 && j==3) aux1 =collin_N2plusE(ttemp);
else if(i==2 && j==4) aux1 =collin_N2plusN2(ttemp);
else if(i==3 && j==4) aux1 =collin_EN2(ttemp);
else aux1= 1;
}
mmass_i=MATERIAL_PROP(spi,PROP_mwi);
aux2=1E-03*(mmass_i/(6.022E+23));
aux =((KB*ttemp)/Pressure)*(3/8)*pow((((M_PI*KB*ttemp)*(aux2+aux3))/(2*(aux2*aux3))),0.5)*(1/(M_PI*1E-20*aux1));
C_UDMI(c,t,1)=aux;

}
return aux;
}
while iterating i get the error to be "mass diffusivity is Zero " please check the material property .
please give me few suggestions to overcome the above issue.

or whether i have to include UDS diffusivity for solving each diffusion of species. For example-N2,N2+,N,N+,e are the species considered and Dij - i= N2 and j=N then i want to calculated diffusion of N2 into N similary N2 into N2plus and so on.

Kindly give me few suggestions to continue my work.