 Haven ratio

With the explicitly stated convention $H_R=D_{\mathrm{tr}}/D_{\sigma }$, the tracer and collective diffusion coefficients are related by $D_{\sigma }=D_{\mathrm{tr}}/H_R$. The Nernst-Einstein relation then gives $\sigma =n{q}^2{D}_{\mathrm{tr}}/(H_R{k}_{B}T)$. State the convention, since reciprocal definitions can otherwise cause confusion.