diff --git a/org/qmckl_nucleus.org b/org/qmckl_nucleus.org
index 82afe85..634fb46 100644
--- a/org/qmckl_nucleus.org
+++ b/org/qmckl_nucleus.org
@@ -1144,7 +1144,7 @@ assert(rep - 318.2309879436158 < 1.e-10);
    ~en_potential~ stores the ~en~ potential energy
 
    \[
-   \mathcal{V}_{en} = \sum_{i=1}^{N_e}\sum_{A=1}^{N_n}\frac{Z_A}{r_{iA}}
+   \mathcal{V}_{en} = -\sum_{i=1}^{N_e}\sum_{A=1}^{N_n}\frac{Z_A}{r_{iA}}
    \]
 
    where \(\mathcal{V}_{en}\) is the ~en~ potential, \[r_{iA}\] the ~en~
@@ -1289,7 +1289,7 @@ integer function qmckl_compute_en_potential_f(context, elec_num, nucl_num, walk_
   do nw=1,walk_num
     do j=1,nucl_num
       do i=1,elec_num
-        en_pot(nw) = en_pot(nw) + charge(j)/(en_distance(i,j,nw))
+        en_pot(nw) = en_pot(nw) - charge(j)/(en_distance(i,j,nw))
       end do
     end do
   end do