message: Fixed incorrect variable in weighting docs.
diff: @@ -174,7 +174,7 @@ contribution of individual atoms by scaling the amplitude of their Gaussian
  contributions:
  .. math::
  - \rho^Z(\mathbf{r}) = \sum_i^{\lvert Z_i \rvert} w(r)e^{-1/2\sigma^2 \lvert \mathbf{r} - \mathbf{R}_i \rvert^2}
  + \rho^Z(\mathbf{r}) = \sum_i^{\lvert Z_i \rvert} w(\lvert \mathbf{R}_i \rvert)e^{-1/2\sigma^2 \lvert \mathbf{r} - \mathbf{R}_i \rvert^2}
  This approximates the "correct" weighting very well as long as the width of the
  atomic Gaussians (as determined by ``sigma``) is small compared to the
  