\begin{equation}
\varphi(\mathbf{r}) = \sum_{A=1}^{N_\mathrm{atoms}} \frac{Z_A}{|\mathbf{R}_A - \mathbf{r}|} - \int\mathrm{d}\mathbf{r}^\prime\frac{\rho(\mathbf{r}^\prime)}{|\mathbf{r}-\mathbf{r}^\prime|}
\end{equation}