Thank you for the correction - I intended to write the equation as diff(c(x,t),t)=D*diff(c(x,t),x,x). 

In my present work, it is appropriate to consider that D is the same in the two materials, as they have the same composition.

S Carroll, student

Thank you for the correction - I intended to write the equation as diff(c(x,t),t)=D*diff(c(x,t),x,x). 

In my present work, it is appropriate to consider that D is the same in the two materials, as they have the same composition.

S Carroll, student