Forgot to commit the nbr_list checking line in the generalized MC mov…

…e in the MC PR. Addressed comments from marcus.

chiron/mcmc.py

@@ -412,6 +412,7 @@ def apply(
         log.debug(f"Initial positions are {initial_positions} nm.")
         # Propose perturbed positions. Modifying the reference changes the sampler state.
         proposed_positions = self._propose_positions(initial_positions)
+
         log.debug(f"Proposed positions are {proposed_positions} nm.")
         # Compute the energy of the proposed positions.
         if atom_subset is None:
@@ -420,6 +421,10 @@ def apply(
             sampler_state.x0 = sampler_state.x0.at[jnp.array(atom_subset)].set(
                 proposed_positions
             )
+        if nbr_list is not None:
+            if nbr_list.check(sampler_state.x0):
+                nbr_list.build(sampler_state.x0, sampler_state.box_vectors)
+
         proposed_energy = thermodynamic_state.get_reduced_potential(
             sampler_state, nbr_list
         )  # NOTE: in kT

chiron/neighbors.py

@@ -39,6 +39,10 @@ def __init__(
                     )
 
                 self.box_vectors = box_vectors
+            else:
+                raise TypeError(
+                    f"box_vectors must be a jnp.array or unit.Quantity, not {type(box_vectors)}"
+                )
 
     @property
     def box_vectors(self) -> jnp.array: