In 1948, Lawrence Stamper Darken published an article entitled "Diffusion, Mobility and Their Interrelation through Free Energy in Binary Metallic Systems", in which he derived two equations describing solid-state diffusion in binary solutions. Specifically, the equations Darken created relate “binary chemical diffusion coefficient to the intrinsic and self diffusion coefficients”. The equations apply to cases when a solid solution's two interdiffusing components do not have the same coefficient of diffusion. The result of this article had a large impact on the understanding of solid state diffusion and as a result the equations have come to be known as “Darken’s equations”.