diff --git a/src/graph_pes/models/pairwise.py b/src/graph_pes/models/pairwise.py
index f6490548..ecb7c55d 100644
--- a/src/graph_pes/models/pairwise.py
+++ b/src/graph_pes/models/pairwise.py
@@ -10,7 +10,6 @@
     keys,
     neighbour_distances,
 )
-from graph_pes.nn import PositiveParameter
 from graph_pes.transform import PerAtomScale, PerAtomShift
 from jaxtyping import Float
 from torch import Tensor
@@ -98,10 +97,9 @@ class LennardJones(PairPotential):
         \frac{\sigma}{r_{ij}} \right)^{12} - \left( \frac{\sigma}{r_{ij}}
         \right)^{6} \right]
 
-    where :math:`r_{ij}` is the distance between atoms :math:`i` and :math:`j`.
-    Internally, :math:`\varepsilon` and :math:`\sigma` are stored as
-    :class:`PositiveParameter <graph_pes.nn.PositiveParamerer>` instances,
-    which ensures that they are kept strictly positive during training.
+    where :math:`r_{ij}` is the distance between atoms :math:`i` and :math:`j`,
+    and :math:`\varepsilon` and :math:`\sigma` are strictly positive
+    paramters that control the depth and width of the potential well,
 
     Parameters
     ----------
@@ -154,29 +152,19 @@ class Morse(PairPotential):
         V(r_{ij}, Z_i, Z_j) = V(r_{ij}) = D (1 - e^{-a(r_{ij} - r_0)})^2
 
     where :math:`r_{ij}` is the distance between atoms :math:`i` and :math:`j`,
-    and :math:`D`, :math:`a` and :math:`r_0` control the depth, width and
-    center of the potential well, respectively. Internally, these are stored
-    as :class:`PositiveParameter` instances.
-
-    Attributes
-    ----------
-    D: :class:`PositiveParameter <graph_pes.nn.PositiveParameter>`
-        The depth of the potential.
-    a: :class:`PositiveParameter <graph_pes.nn.PositiveParameter>`
-        The width of the potential.
-    r0: :class:`PositiveParameter <graph_pes.nn.PositiveParameter>`
-        The center of the potential.
+    and :math:`D`, :math:`a` and :math:`r_0` are strictly positive parameters
+    that control the depth, width and center of the potential well respectively.
     """
 
-    def __init__(self):
+    def __init__(self, D: float = 0.1, a: float = 3.0, r0: float = 1.0):
         super().__init__()
-        self.D = PositiveParameter(0.1)
-        self.a = PositiveParameter(1.0)
-        self.r0 = PositiveParameter(0.5)
+        self._log_D = torch.nn.Parameter(torch.tensor(D).log())
+        self._log_a = torch.nn.Parameter(torch.tensor(a).log())
+        self._log_r0 = torch.nn.Parameter(torch.tensor(r0).log())
 
         # D is a scaling term, so only need to learn a shift
         # parameter (rather than a shift and scale)
-        self._energy_summation = EnergySummation(local_transform=PerAtomScale())
+        self.energy_summation = EnergySummation(local_transform=PerAtomScale())
 
     def interaction(
         self, r: torch.Tensor, Z_i: torch.Tensor, Z_j: torch.Tensor
@@ -193,18 +181,19 @@ def interaction(
         Z_j : torch.Tensor
             The atomic numbers of the neighbours. (unused)
         """
-        return self.D * (1 - torch.exp(-self.a * (r - self.r0))) ** 2
+        D, a, r0 = self._log_D.exp(), self._log_a.exp(), self._log_r0.exp()
+        return D * (1 - torch.exp(-a * (r - r0))) ** 2
 
     def pre_fit(self, graph: AtomicGraphBatch):
         super().pre_fit(graph)
 
         # set the potential depth to be shallow
-        self.D = PositiveParameter(0.1)
+        self._log_D = torch.nn.Parameter(torch.tensor(0.1).log())
 
         # set the center of the well to be close to the minimum pair-wise
         # distance
         d = torch.quantile(neighbour_distances(graph), 0.01)
-        self.r0 = PositiveParameter(d)
+        self._log_r0 = torch.nn.Parameter(d.log())
 
-        # set the width to be broad
-        self.a = PositiveParameter(0.5)
+        # set the width to be "reasonable"
+        self._log_a = torch.nn.Parameter(torch.tensor(3.0).log())
diff --git a/src/graph_pes/models/zoo.py b/src/graph_pes/models/zoo.py
index c40a1133..b7a0c5ff 100644
--- a/src/graph_pes/models/zoo.py
+++ b/src/graph_pes/models/zoo.py
@@ -1,5 +1,5 @@
 from .painn import PaiNN
-from .pairwise import LennardJones
+from .pairwise import LennardJones, Morse
 from .schnet import SchNet
 from .tensornet import TensorNet
 
@@ -8,4 +8,5 @@
     "LennardJones",
     "SchNet",
     "TensorNet",
+    "Morse",
 ]
diff --git a/src/graph_pes/nn.py b/src/graph_pes/nn.py
index fe87aba6..e8e651c4 100644
--- a/src/graph_pes/nn.py
+++ b/src/graph_pes/nn.py
@@ -405,14 +405,18 @@ def constrained_value(self):
 
 
 class HaddamardProduct(nn.Module):
-    def __init__(self, *components: nn.Module):
+    def __init__(self, *components: nn.Module, left_aligned: bool = False):
         super().__init__()
         self.components: list[nn.Module] = nn.ModuleList(components)  # type: ignore
+        self.left_aligned = left_aligned
 
     def forward(self, x):
-        out = 1
+        out = torch.scalar_tensor(1)
         for component in self.components:
-            out = out * component(x)
+            if self.left_aligned:
+                out = left_aligned_mul(out, component(x))
+            else:
+                out = out * component(x)
         return out
 
 
diff --git a/tests/test_torchscript.py b/tests/test_torchscript.py
index e2e47102..5faab000 100644
--- a/tests/test_torchscript.py
+++ b/tests/test_torchscript.py
@@ -4,7 +4,7 @@
 import torch
 from ase.build import molecule
 from graph_pes.data import batch_graphs, convert_to_atomic_graph
-from graph_pes.models.zoo import LennardJones, PaiNN, SchNet, TensorNet
+from graph_pes.models.zoo import LennardJones, Morse, PaiNN, SchNet, TensorNet
 
 graph = convert_to_atomic_graph(molecule("CH3CH2OH"), cutoff=1.5)
 batch = batch_graphs([graph, graph])
@@ -13,6 +13,7 @@
     PaiNN(),
     SchNet(),
     TensorNet(),
+    Morse(),
 ]