diff --git a/src/morered/configs/experiment/vp_gauss_ddpm.yaml b/src/morered/configs/experiment/vp_gauss_ddpm.yaml
index 5df000b..42c1055 100644
--- a/src/morered/configs/experiment/vp_gauss_ddpm.yaml
+++ b/src/morered/configs/experiment/vp_gauss_ddpm.yaml
@@ -48,8 +48,7 @@ data:
       diffusion_process: ${globals.diffusion_process}
       time_key: ${globals.time_target_key}
 
-    - _target_: schnetpack.transform.MatScipyNeighborList
-      cutoff: ${globals.cutoff}
+    - _target_: morered.transform.AllToAllNeighborList
     - _target_: schnetpack.transform.CastTo32
 
 model:
diff --git a/src/morered/sampling/ddpm.py b/src/morered/sampling/ddpm.py
index e38c54a..f4658e6 100644
--- a/src/morered/sampling/ddpm.py
+++ b/src/morered/sampling/ddpm.py
@@ -118,7 +118,7 @@ def denoise(
 
         # set all atoms as neighbors and compute neighbors only once before starting.
         if not self.recompute_neighbors:
-            batch = compute_neighbors(batch, cutoff=9999999.0, device=self.device)
+            batch = compute_neighbors(batch, fully_connected=True, device=self.device)
 
         # history of the reverse steps
         hist = []
diff --git a/src/morered/sampling/morered.py b/src/morered/sampling/morered.py
index d81cd05..530a885 100644
--- a/src/morered/sampling/morered.py
+++ b/src/morered/sampling/morered.py
@@ -93,7 +93,7 @@ def denoise(
 
         # set all atoms as neighbors and compute neighbors only once before starting.
         if not self.recompute_neighbors:
-            batch = compute_neighbors(batch, cutoff=9999999.0, device=self.device)
+            batch = compute_neighbors(batch, fully_connected=True, device=self.device)
 
         # initialize convergence flag for each molecule
         converged = torch.zeros_like(
diff --git a/src/morered/transform/transforms.py b/src/morered/transform/transforms.py
index b81960a..46c394e 100644
--- a/src/morered/transform/transforms.py
+++ b/src/morered/transform/transforms.py
@@ -8,7 +8,30 @@
 from morered.processes.base import DiffusionProcess
 from morered.utils import batch_center_systems
 
-__all__ = ["BatchSubtractCenterOfMass", "Diffuse"]
+__all__ = ["AllToAllNeighborList", "BatchSubtractCenterOfMass", "Diffuse"]
+
+
+class AllToAllNeighborList(trn.NeighborListTransform):
+    """
+    Calculate a full neighbor list for all atoms in the system.
+    Faster than other methods and useful for small systems.
+    """
+
+    def __init__(self):
+        # pass dummy large cutoff as all neighbors are connceted
+        super().__init__(cutoff=1e8)
+
+    def _build_neighbor_list(self, Z, positions, cell, pbc, cutoff):
+        n_atoms = Z.shape[0]
+        idx_i = torch.arange(n_atoms).repeat_interleave(n_atoms)
+        idx_j = torch.arange(n_atoms).repeat(n_atoms)
+
+        mask = idx_i != idx_j
+        idx_i = idx_i[mask]
+        idx_j = idx_j[mask]
+
+        offset = torch.zeros(n_atoms * (n_atoms - 1), 3, dtype=positions.dtype)
+        return idx_i, idx_j, offset
 
 
 class BatchSubtractCenterOfMass(trn.Transform):
diff --git a/src/morered/utils.py b/src/morered/utils.py
index 306d9d0..d426188 100644
--- a/src/morered/utils.py
+++ b/src/morered/utils.py
@@ -4,14 +4,15 @@
 from typing import Dict, Optional
 
 import numpy as np
+import schnetpack.transform as trn
 import torch
 from ase import Atoms, build
 from ase.data import chemical_symbols, covalent_radii
-from tqdm import tqdm
-
-import schnetpack.transform as trn
 from schnetpack import properties
 from schnetpack.data.loader import _atoms_collate_fn
+from tqdm import tqdm
+
+import morered as mrd
 from morered.bonds import allowed_bonds_dict, bonds1, bonds2, bonds3
 
 
@@ -70,6 +71,7 @@ def compute_neighbors(
     old_batch,
     neighbor_list_trn: Optional[trn.Transform] = None,
     cutoff=5.0,
+    fully_connected=False,
     additional_keys=[],
     device=None,
 ):
@@ -80,6 +82,8 @@ def compute_neighbors(
         old_batch: batch of systems to compute the neighbors for
         neighbor_list_trn: transform to compute the neighbors
         cutoff: cutoff radius for the neighbor list
+        fully_connected: if True, all atoms are connected to each other.
+                            Ignores the cutoff.
         additional_keys: additional keys to be included in the new batch
         device: Pytorch device
     """
@@ -90,7 +94,12 @@ def compute_neighbors(
     f_dtype = old_batch[properties.R].dtype
 
     # initialize the neighbor list transform
-    neighbors_calculator = neighbor_list_trn or trn.MatScipyNeighborList(cutoff=cutoff)
+    if fully_connected:
+        neighbors_calculator = mrd.transform.AllToAllNeighborList()
+    else:
+        neighbors_calculator = neighbor_list_trn or trn.MatScipyNeighborList(
+            cutoff=cutoff
+        )
 
     batch = []