diff --git a/.github/workflows/docs.yml b/.github/workflows/docs.yml
index 8c8200a..5c7f682 100644
--- a/.github/workflows/docs.yml
+++ b/.github/workflows/docs.yml
@@ -25,6 +25,9 @@ jobs:
           python -m pip install tox
 
       - name: build documentation
+        env:
+          # Use the CPU only version of torch when building/running the code
+          PIP_EXTRA_INDEX_URL: https://download.pytorch.org/whl/cpu
         run: tox -e docs
 
       - name: put documentation in the website
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 1847d7c..c7854ea 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -23,8 +23,6 @@ jobs:
             python-version: "3.12"
           - os: macos-14
             python-version: "3.12"
-          - os: windows-2019
-            python-version: "3.12"
     steps:
       - uses: actions/checkout@v4
         with:
@@ -42,3 +40,5 @@ jobs:
 
       - name: run tests
         run: tox
+        env:
+          PIP_EXTRA_INDEX_URL: https://download.pytorch.org/whl/cpu
diff --git a/CONTRIBUTORS b/CONTRIBUTORS
new file mode 100644
index 0000000..12d49ee
--- /dev/null
+++ b/CONTRIBUTORS
@@ -0,0 +1,4 @@
+Matthias Kellner
+Yuxuan Zhang
+Ruben Rodriguez Madrid
+Guillaume Fraux
\ No newline at end of file
diff --git a/README.md b/README.md
index 6698b47..fd60cec 100644
--- a/README.md
+++ b/README.md
@@ -2,3 +2,80 @@
 
 [![Documentation](https://img.shields.io/badge/docs-latest-brightgreen.svg)](https://lab-cosmo.github.io/ShiftML/latest/)
 ![Tests](https://img.shields.io/github/check-runs/lab-cosmo/ShiftML/main?logo=github&label=tests)
+
+**Disclaimer: This package is still under development and should be used with caution.**
+
+Welcome to ShitML, a python package for the prediction of chemical shieldings of organic solids and beyond.
+
+
+
+## Usage
+
+Use ShiftML with the atomsitic simulation environment to obtain fast estimates of chemical shieldings:
+
+```python
+
+from ase.build import bulk
+from shiftml.ase import ShiftML
+
+frame = bulk("C", "diamond", a=3.566)
+calculator = ShiftML("ShiftML1.0")
+
+cs_iso = calc.get_cs_iso(frame)
+
+print(cs_iso)
+
+```
+
+## IMPORTANT: Install pre-instructions before PiPy release
+
+Rascaline-torch, one of the main dependence of ShiftML, requires CXX and Rust compilers to be built from source.
+Most systems come already with configured C/C++ compilers (make sure that some environment variables CC and CXX are set
+and gcc can be found), but Rust typically needs to be installed manually.
+For ease of use we strongly recommend to use some sort of package manager to install Rust, such as conda and a fresh environment.
+
+
+```bash
+
+conda create -n shiftml python=3.10
+conda activate shiftml
+conda install -c conda-forge rust
+
+```
+
+
+## Installation
+
+To install ShiftML, you can use clone this repository and install it using pip, a pipy release will follow soon:
+
+```
+pip install --extra-index-url https://download.pytorch.org/whl/cpu .
+```
+
+## The code that makes it work
+
+This project would not have been possible without the following packages:
+
+- Metadata and model handling: [metatensor](https://github.com/lab-cosmo/metatensor)
+- Atomic descriptor engine: [rascaline](https://github.com/Luthaf/rascaline)
+
+## Documentation
+
+The documentation is available [here](https://lab-cosmo.github.io/ShiftML/latest/).
+
+## Contributors
+
+Matthias Kellner\
+Yuxuan Zhang\
+Ruben Rodriguez Madrid\
+Guillaume Fraux
+
+## References
+
+This package is based on the following papers:
+
+- Chemical shifts in molecular solids by machine learning - Paruzzo et al. [[1](https://doi.org/10.1038%2Fs41467-018-06972-x)]
+- A Bayesian approach to NMR crystal structure determination - Engel et al. [[2](https://doi.org/10.1039%2Fc9cp04489b)]
+- A Machine Learning Model of Chemical Shifts for Chemically and\
+Structurally Diverse Molecular Solids - Cordova et al. [[3](https://doi.org/10.1021/acs.jpcc.2c03854)]
+
diff --git a/pyproject.toml b/pyproject.toml
index ada7c00..84b3a3f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -6,11 +6,16 @@ authors = [
 ]
 
 dependencies = [
+    "numpy",
+    "ase==3.22.1",
+    "metatensor[torch]",
+    "platformdirs",
+    "rascaline-torch@git+https://github.com/luthaf/rascaline@e215461#subdirectory=python/rascaline-torch",
 ]
 
 readme = "README.md"
 license = {text = "BSD-3-Clause"}
-description = "TODO"
+description = "Predictions of chemical shieldings using machine learning"
 
 
 [project.urls]
diff --git a/src/shiftml/ase/__init__.py b/src/shiftml/ase/__init__.py
new file mode 100644
index 0000000..daa39be
--- /dev/null
+++ b/src/shiftml/ase/__init__.py
@@ -0,0 +1 @@
+from .calculator import ShiftML  # noqa: F401
diff --git a/src/shiftml/ase/calculator.py b/src/shiftml/ase/calculator.py
new file mode 100644
index 0000000..e0eac0b
--- /dev/null
+++ b/src/shiftml/ase/calculator.py
@@ -0,0 +1,158 @@
+import logging
+import os
+import urllib.request
+
+from metatensor.torch.atomistic import ModelOutput
+from metatensor.torch.atomistic.ase_calculator import MetatensorCalculator
+from platformdirs import user_cache_path
+
+# For now we set the logging level to DEBUG
+logformat = "%(asctime)s - %(levelname)s - %(message)s"
+logging.basicConfig(level=logging.DEBUG, format=logformat)
+
+
+url_resolve = {
+    "ShiftML1.0": "https://tinyurl.com/3xwec68f",
+    "ShiftML1.1": "https://tinyurl.com/53ymkhvd",
+}
+
+resolve_outputs = {
+    "ShiftML1.0": {"mtt::cs_iso": ModelOutput(quantity="", unit="ppm", per_atom=True)},
+    "ShiftML1.1": {"mtt::cs_iso": ModelOutput(quantity="", unit="ppm", per_atom=True)},
+}
+
+resolve_fitted_species = {
+    "ShiftML1.0": set([1, 6, 7, 8, 16]),
+    "ShiftML1.1": set([1, 6, 7, 8, 16]),
+}
+
+
+class ShiftML(MetatensorCalculator):
+    """
+    ShiftML calculator for ASE
+    """
+
+    def __init__(self, model_version, force_download=False):
+        """
+        Initialize the ShiftML calculator
+
+        Parameters
+        ----------
+        model_version : str
+            The version of the ShiftML model to use. Supported versions are
+            "ShiftML1.0".
+        force_download : bool, optional
+            If True, the model will be downloaded even if it is already in the cache.
+            The chache-dir will be determined via the platformdirs library and should
+            comply with user settings such as XDG_CACHE_HOME.
+            Default is False.
+        """
+
+        try:
+            # The rascline import is necessary because
+            # it is required for the scripted model
+            import rascaline.torch
+
+            logging.info(rascaline.torch.__version__)
+            logging.info("rascaline-torch is installed, importing rascaline-torch")
+
+            assert (
+                rascaline.torch.__version__ == "0.1.0.dev558"
+            ), "wrong rascaline-torch installed"
+
+        except ImportError:
+            raise ImportError(
+                "rascaline-torch is required for ShiftML calculators,\
+                 please install it using\
+                 pip install git+https://github.com/luthaf/rascaline#subdirectory\
+                 =python/rascaline-torch"
+            )
+
+        try:
+            url = url_resolve[model_version]
+            self.outputs = resolve_outputs[model_version]
+            self.fitted_species = resolve_fitted_species[model_version]
+            logging.info("Found model version in url_resolve")
+            logging.info("Resolving model version to model files at url: ", url)
+        except KeyError:
+            raise ValueError(
+                f"Model version {model_version} is not supported.\
+                    Supported versions are {list(url_resolve.keys())}"
+            )
+
+        cachedir = os.path.expanduser(
+            os.path.join(user_cache_path(), "shiftml", str(model_version))
+        )
+
+        # check if model is already downloaded
+        try:
+            if not os.path.exists(cachedir):
+                os.makedirs(cachedir)
+            model_file = os.path.join(cachedir, model_version + ".pt")
+
+            if os.path.exists(model_file) and force_download:
+                logging.info(
+                    f"Found {model_version} in cache, but force_download is set to True"
+                )
+                logging.info(
+                    f"Removing {model_version} from cache and downloading it again"
+                )
+                os.remove(model_file)
+                download = True
+
+            else:
+                if os.path.exists(model_file):
+                    logging.info(
+                        f"Found {model_version}  in cache,\
+                         and importing it from here: {cachedir}"
+                    )
+                    download = False
+                else:
+                    logging.info("Model not found in cache, downloading it")
+                    download = True
+
+            if download:
+                urllib.request.urlretrieve(url, model_file)
+                logging.info(f"Downloaded {model_version} and saved to {cachedir}")
+
+        except urllib.error.URLError as e:
+            logging.error(
+                f"Failed to download {model_version} from {url}. URL Error: {e.reason}"
+            )
+            raise e
+        except urllib.error.HTTPError as e:
+            logging.error(
+                f"Failed to download {model_version} from {url}.\
+                  HTTP Error: {e.code} - {e.reason}"
+            )
+            raise e
+        except Exception as e:
+            logging.error(
+                f"An unexpected error occurred while downloading\
+                  {model_version} from {url}: {e}"
+            )
+            raise e
+
+        super().__init__(model_file)
+
+    def get_cs_iso(self, atoms):
+        """
+        Compute the shielding values for the given atoms object
+        """
+
+        assert (
+            "mtt::cs_iso" in self.outputs.keys()
+        ), "model does not support chemical shielding prediction"
+
+        if not set(atoms.get_atomic_numbers()).issubset(self.fitted_species):
+            raise ValueError(
+                f"Model is fitted only for the following atomic numbers:\
+                {self.fitted_species}. The atomic numbers in the atoms object are:\
+                {set(atoms.get_atomic_numbers())}. Please provide an atoms object\
+                with only the fitted species."
+            )
+
+        out = self.run_model(atoms, self.outputs)
+        cs_iso = out["mtt::cs_iso"].block(0).values.detach().numpy()
+
+        return cs_iso
diff --git a/tests/test_ase.py b/tests/test_ase.py
new file mode 100644
index 0000000..69f8ca3
--- /dev/null
+++ b/tests/test_ase.py
@@ -0,0 +1,75 @@
+# TODO: test for rotational invariance, translation invariance,
+# and permutation, as well as size extensivity
+import numpy as np
+import pytest
+from ase.build import bulk
+
+from shiftml.ase import ShiftML
+
+expected_output = np.array([137.5415, 137.5415])
+
+
+def test_shiftml1_regression():
+    """Regression test for the ShiftML1.0 model."""
+
+    frame = bulk("C", "diamond", a=3.566)
+    model = ShiftML("ShiftML1.0", force_download=True)
+    out = model.get_cs_iso(frame)
+
+    assert np.allclose(
+        out.flatten(), expected_output
+    ), "ShiftML1 failed regression test"
+
+
+def test_shiftml1_rotational_invariance():
+    """Rotational invariance test for the ShiftML1.0 model."""
+
+    frame = bulk("C", "diamond", a=3.566)
+    model = ShiftML("ShiftML1.0")
+    out = model.get_cs_iso(frame)
+
+    assert np.allclose(
+        out.flatten(), expected_output
+    ), "ShiftML1 failed regression test"
+
+    # Rotate the frame by 90 degrees about the z-axis
+    frame.rotate(90, "z")
+
+    out_rotated = model.get_cs_iso(frame)
+
+    assert np.allclose(
+        out_rotated.flatten(), expected_output
+    ), "ShiftML1 failed rotational invariance test"
+
+
+def test_shiftml1_size_extensivity_test():
+    """Test ShiftML1.0 for translational invariance."""
+
+    frame = bulk("C", "diamond", a=3.566)
+    model = ShiftML("ShiftML1.0")
+    out = model.get_cs_iso(frame)
+
+    assert np.allclose(
+        out.flatten(), expected_output
+    ), "ShiftML1 failed regression test"
+
+    frame = frame * (2, 1, 1)
+    out = model.get_cs_iso(frame)
+
+    assert np.allclose(
+        out.flatten(), np.stack([expected_output, expected_output]).flatten()
+    ), "ShiftML1 failed size extensivity test"
+
+
+def test_shftml1_fail_invalid_species():
+    """Test ShiftML1.o for non-fitted species"""
+
+    frame = bulk("Si", "diamond", a=3.566)
+    model = ShiftML("ShiftML1.0")
+    with pytest.raises(ValueError) as exc_info:
+        model.get_cs_iso(frame)
+
+    assert exc_info.type == ValueError
+    assert "Model is fitted only for the following atomic numbers:" in str(
+        exc_info.value
+    )
diff --git a/tests/test_dummy.py b/tests/test_dummy.py
deleted file mode 100644
index 95c5ab7..0000000
--- a/tests/test_dummy.py
+++ /dev/null
@@ -1,2 +0,0 @@
-def test_example():
-    assert 1 + 1 == 2
diff --git a/tests/test_regression_pretrained.py b/tests/test_regression_pretrained.py
new file mode 100644
index 0000000..eca1e79
--- /dev/null
+++ b/tests/test_regression_pretrained.py
@@ -0,0 +1,37 @@
+import numpy as np
+from ase.build import bulk
+
+from shiftml.ase import ShiftML
+
+expected_outputs = {
+    "ShiftML1.0": np.array([137.5415, 137.5415]),
+    "ShiftML1.1": np.array([163.07251, 163.07251]),
+}
+
+
+def test_shiftml1_regression():
+    """Regression test for the ShiftML1.0 model."""
+
+    MODEL = "ShiftML1.0"
+
+    frame = bulk("C", "diamond", a=3.566)
+    model = ShiftML(MODEL, force_download=True)
+    out = model.get_cs_iso(frame)
+
+    assert np.allclose(
+        out.flatten(), expected_outputs[MODEL]
+    ), "ShiftML1.0 failed regression test"
+
+
+def test_shiftml1_1_regression():
+    """Regression test for the ShiftML1.1 model."""
+
+    MODEL = "ShiftML1.1"
+
+    frame = bulk("C", "diamond", a=3.566)
+    model = ShiftML(MODEL, force_download=True)
+    out = model.get_cs_iso(frame)
+
+    assert np.allclose(
+        out.flatten(), expected_outputs[MODEL]
+    ), "ShiftML1.1 failed regression test"