diff --git a/torch_sim/models/orb.py b/torch_sim/models/orb.py
index 3563f2a9..3b763aeb 100644
--- a/torch_sim/models/orb.py
+++ b/torch_sim/models/orb.py
@@ -104,10 +104,7 @@ def state_to_atom_graphs(  # noqa: PLR0915
         system_config = SystemConfig(radius=6.0, max_num_neighbors=20)
 
     # Handle batch information if present
-    if state.batch is not None:
-        n_node = torch.bincount(state.batch)
-    else:
-        n_node = torch.tensor([len(state.positions)])
+    n_node = torch.bincount(state.batch)
 
     # Set default dtype if not provided
     output_dtype = torch.get_default_dtype() if output_dtype is None else output_dtype
@@ -148,45 +145,46 @@ def state_to_atom_graphs(  # noqa: PLR0915
     if wrap and (torch.any(row_vector_cell != 0) and torch.any(pbc)):
         positions = feat_util.batch_map_to_pbc_cell(positions, row_vector_cell, n_node)
 
-    # Compute edges of the graph
-    edge_index, edge_vectors, unit_shifts, batch_num_edges = (
-        feat_util.batch_compute_pbc_radius_graph(
-            positions=positions,
-            cells=row_vector_cell,
-            pbc=pbc.unsqueeze(0).repeat(len(n_node), 1),
-            radius=system_config.radius,
-            n_node=n_node,
-            max_number_neighbors=torch.tensor([max_num_neighbors] * len(n_node)),
-            edge_method=edge_method,
-            half_supercell=half_supercell,
-            device=device,
-        )
-    )
-    senders, receivers = edge_index[0], edge_index[1]
-
     n_systems = state.batch.max().item() + 1
+
+    # Prepare lists to collect data from each system
+    all_edges = []
+    all_vectors = []
+    all_unit_shifts = []
+    num_edges = []
     node_feats_list = []
     edge_feats_list = []
     graph_feats_list = []
-    system_edges = torch.repeat_interleave(
-        torch.arange(n_systems, device=state.device), batch_num_edges
-    )
+
+    # Process each system in a single loop
+    offset = 0
     for i in range(n_systems):
         batch_mask = state.batch == i
-        system_edge_mask = system_edges == i
-        try:
-            positions_per_system = positions[batch_mask]
-            atomic_numbers_per_system = atomic_numbers[batch_mask]
-            atomic_numbers_embedding_per_system = atomic_numbers_embedding[batch_mask]
-            edge_vectors_per_system = edge_vectors[system_edge_mask]
-            unit_shifts_per_system = unit_shifts[system_edge_mask]
-        except Exception:  # noqa: BLE001
-            import pdb  # noqa: T100
-
-            pdb.set_trace()  # noqa: T100
-
+        positions_per_system = positions[batch_mask]
+        atomic_numbers_per_system = atomic_numbers[batch_mask]
+        atomic_numbers_embedding_per_system = atomic_numbers_embedding[batch_mask]
         cell_per_system = row_vector_cell[i]
         pbc_per_system = pbc
+
+        # Compute edges directly for this system
+        edges, vectors, unit_shifts = feat_util.compute_pbc_radius_graph(
+            positions=positions_per_system,
+            cell=cell_per_system,
+            pbc=pbc_per_system,
+            radius=system_config.radius,
+            max_number_neighbors=max_num_neighbors,
+            edge_method=edge_method,
+            half_supercell=half_supercell,
+            device=device,
+        )
+
+        # Adjust indices for the global batch
+        all_edges.append(edges + offset)
+        all_vectors.append(vectors)
+        all_unit_shifts.append(unit_shifts)
+        num_edges.append(len(edges[0]))
+
+        # Calculate lattice parameters
         lattice_per_system = torch.from_numpy(
             cell_to_cellpar(cell_per_system.squeeze(0).cpu().numpy())
         )
@@ -202,8 +200,8 @@ def state_to_atom_graphs(  # noqa: PLR0915
         }
 
         edge_feats = {
-            "vectors": edge_vectors_per_system,
-            "unit_shifts": unit_shifts_per_system,
+            "vectors": vectors,
+            "unit_shifts": unit_shifts,
         }
 
         graph_feats = {
@@ -221,6 +219,16 @@ def state_to_atom_graphs(  # noqa: PLR0915
         edge_feats_list.append(edge_feats)
         graph_feats_list.append(graph_feats)
 
+        # Update offset for next system
+        offset += len(positions_per_system)
+
+    # Concatenate all the edge data
+    edge_index = torch.cat(all_edges, dim=1)
+    unit_shifts = torch.cat(all_unit_shifts, dim=0)
+    batch_num_edges = torch.tensor(num_edges, dtype=torch.int64, device=device)
+
+    senders, receivers = edge_index[0], edge_index[1]
+
     # Create and return AtomGraphs object
     return AtomGraphs(
         senders=senders,