diff --git a/pyqint/cgf.py b/pyqint/cgf.py
index 4ec5c6c..3765c3c 100644
--- a/pyqint/cgf.py
+++ b/pyqint/cgf.py
@@ -1,5 +1,6 @@
 from .gto import gto
 from .pyqint import PyCGF
+from . import spherical_harmonics as sh
 
 class cgf:
     """
@@ -48,6 +49,17 @@ def add_gto(self, c, alpha, l, m, n):
         self.gtos.append(gto(c, self.p, alpha, l, m, n))
         self.cgf.add_gto(c, alpha, l, m, n)
 
+    def add_spherical_gto(self, c, alpha, l, m):
+        """
+        Add Spherical Gaussian Type Orbital to Contracted Gaussian Function.
+        l and m are the coefficients of the requested spherical harmonic function. 
+        l must be <= 6 and -l <= m <= l.
+        """
+        if not l <= 6 or not abs(m) <=l:
+            raise ValueError("l must be <= 6 and -l <= m <= l")
+        for gto in sh.spherical_harmonics[l][m]:
+            self.add_gto(gto[0] * c, alpha, gto[1][0], gto[1][1], gto[1][2])
+
     def get_amp_f(self, x, y, z):
         """
         Get the amplitude of the wave function at position r
diff --git a/pyqint/spherical_harmonics.py b/pyqint/spherical_harmonics.py
new file mode 100644
index 0000000..e8e5a73
--- /dev/null
+++ b/pyqint/spherical_harmonics.py
@@ -0,0 +1,294 @@
+"""
+coeffecients of spherical harmonics up to l=6 for cartesian gaussian orbitals.
+The format is:
+spherical_harmonics[l][m] = [[c, [l_x, l_y, l_z], ...]
+where l and m are the spherical harmonic coefficents, c is the weight
+and [l_x, l_y, l_z] are the cartesian exponents.
+"""
+
+spherical_harmonics = {
+  0: {
+    0: [
+      [1.0, [0, 0, 0]]
+    ]
+  },
+  1: {
+    -1: [
+      [1.0, [0, 1, 0]]
+    ],
+    0: [
+      [1.0, [0, 0, 1]]
+    ],
+    1: [
+      [1.0, [1, 0, 0]]
+    ]
+  },
+  2: {
+    -2: [
+      [1.0, [1, 1, 0]]
+    ],
+    -1: [
+      [1.0, [0, 1, 1]]
+    ],
+    0: [
+      [-0.5, [2, 0, 0]],
+      [-0.5, [0, 2, 0]],
+      [1.0, [0, 0, 2]]
+    ],
+    1: [
+      [1.0, [1, 0, 1]]
+    ],
+    2: [
+      [0.8660254037844386, [2, 0, 0]],
+      [-0.8660254037844386, [0, 2, 0]]
+    ]
+  },
+  3: {
+    -3: [
+      [1.0606601717798212, [2, 1, 0]],
+      [-0.7905694150420949, [0, 3, 0]]
+    ],
+    -2: [
+      [1.0, [1, 1, 1]]
+    ],
+    -1: [
+      [-0.27386127875258304, [2, 1, 0]],
+      [-0.6123724356957945, [0, 3, 0]],
+      [1.0954451150103321, [0, 1, 2]]
+    ],
+    0: [
+      [-0.6708203932499369, [2, 0, 1]],
+      [-0.6708203932499369, [0, 2, 1]],
+      [1.0, [0, 0, 3]]
+    ],
+    1: [
+      [-0.6123724356957945, [3, 0, 0]],
+      [-0.27386127875258304, [1, 2, 0]],
+      [1.0954451150103321, [1, 0, 2]]
+    ],
+    2: [
+      [0.8660254037844386, [2, 0, 1]],
+      [-0.8660254037844386, [0, 2, 1]]
+    ],
+    3: [
+      [0.7905694150420949, [3, 0, 0]],
+      [-1.0606601717798212, [1, 2, 0]]
+    ]
+  },
+  4: {
+    -4: [
+      [1.118033988749895, [3, 1, 0]],
+      [-1.118033988749895, [1, 3, 0]]
+    ],
+    -3: [
+      [1.0606601717798212, [2, 1, 1]],
+      [-0.7905694150420949, [0, 3, 1]]
+    ],
+    -2: [
+      [-0.4225771273642583, [3, 1, 0]],
+      [-0.4225771273642583, [1, 3, 0]],
+      [1.1338934190276817, [1, 1, 2]]
+    ],
+    -1: [
+      [-0.4008918628686366, [2, 1, 1]],
+      [-0.8964214570007952, [0, 3, 1]],
+      [1.1952286093343936, [0, 1, 3]]
+    ],
+    0: [
+      [0.375, [4, 0, 0]],
+      [0.21957751641341997, [2, 2, 0]],
+      [-0.8783100656536799, [2, 0, 2]],
+      [0.375, [0, 4, 0]],
+      [-0.8783100656536799, [0, 2, 2]],
+      [1.0, [0, 0, 4]]
+    ],
+    1: [
+      [-0.8964214570007952, [3, 0, 1]],
+      [-0.4008918628686366, [1, 2, 1]],
+      [1.1952286093343936, [1, 0, 3]]
+    ],
+    2: [
+      [-0.5590169943749475, [4, 0, 0]],
+      [0.9819805060619657, [2, 0, 2]],
+      [0.5590169943749475, [0, 4, 0]],
+      [-0.9819805060619657, [0, 2, 2]]
+    ],
+    3: [
+      [0.7905694150420949, [3, 0, 1]],
+      [-1.0606601717798212, [1, 2, 1]]
+    ],
+    4: [
+      [0.739509972887452, [4, 0, 0]],
+      [-1.299038105676658, [2, 2, 0]],
+      [0.739509972887452, [0, 4, 0]]
+    ]
+  },
+  5: {
+    -5: [
+      [1.1692679333668567, [4, 1, 0]],
+      [-1.5309310892394863, [2, 3, 0]],
+      [0.701560760020114, [0, 5, 0]]
+    ],
+    -4: [
+      [1.118033988749895, [3, 1, 1]],
+      [-1.118033988749895, [1, 3, 1]]
+    ],
+    -3: [
+      [-0.5229125165837972, [4, 1, 0]],
+      [-0.22821773229381923, [2, 3, 0]],
+      [1.224744871391589, [2, 1, 2]],
+      [0.5229125165837972, [0, 5, 0]],
+      [-0.9128709291752769, [0, 3, 2]]
+    ],
+    -2: [
+      [-0.6454972243679028, [3, 1, 1]],
+      [-0.6454972243679028, [1, 3, 1]],
+      [1.2909944487358056, [1, 1, 3]]
+    ],
+    -1: [
+      [0.1613743060919757, [4, 1, 0]],
+      [0.21128856368212914, [2, 3, 0]],
+      [-0.5669467095138409, [2, 1, 2]],
+      [0.4841229182759271, [0, 5, 0]],
+      [-1.267731382092775, [0, 3, 2]],
+      [1.2909944487358056, [0, 1, 4]]
+    ],
+    0: [
+      [0.625, [4, 0, 1]],
+      [0.36596252735569995, [2, 2, 1]],
+      [-1.0910894511799618, [2, 0, 3]],
+      [0.625, [0, 4, 1]],
+      [-1.0910894511799618, [0, 2, 3]],
+      [1.0, [0, 0, 5]]
+    ],
+    1: [
+      [0.4841229182759271, [5, 0, 0]],
+      [0.21128856368212914, [3, 2, 0]],
+      [-1.267731382092775, [3, 0, 2]],
+      [0.1613743060919757, [1, 4, 0]],
+      [-0.5669467095138409, [1, 2, 2]],
+      [1.2909944487358056, [1, 0, 4]]
+    ],
+    2: [
+      [-0.8539125638299665, [4, 0, 1]],
+      [1.118033988749895, [2, 0, 3]],
+      [0.8539125638299665, [0, 4, 1]],
+      [-1.118033988749895, [0, 2, 3]]
+    ],
+    3: [
+      [-0.5229125165837972, [5, 0, 0]],
+      [0.22821773229381923, [3, 2, 0]],
+      [0.9128709291752769, [3, 0, 2]],
+      [0.5229125165837972, [1, 4, 0]],
+      [-1.224744871391589, [1, 2, 2]]
+    ],
+    4: [
+      [0.739509972887452, [4, 0, 1]],
+      [-1.299038105676658, [2, 2, 1]],
+      [0.739509972887452, [0, 4, 1]]
+    ],
+    5: [
+      [0.701560760020114, [5, 0, 0]],
+      [-1.5309310892394863, [3, 2, 0]],
+      [1.1692679333668567, [1, 4, 0]]
+    ]
+  },
+  6: {
+    -6: [
+      [1.2151388809514738, [5, 1, 0]],
+      [-1.976423537605237, [3, 3, 0]],
+      [1.2151388809514738, [1, 5, 0]]
+    ],
+    -5: [
+      [1.1692679333668567, [4, 1, 1]],
+      [-1.5309310892394863, [2, 3, 1]],
+      [0.701560760020114, [0, 5, 1]]
+    ],
+    -4: [
+      [-0.5982930264130992, [5, 1, 0]],
+      [1.3055824196677337, [3, 1, 2]],
+      [0.5982930264130992, [1, 5, 0]],
+      [-1.3055824196677337, [1, 3, 2]]
+    ],
+    -3: [
+      [-0.8192464664112216, [4, 1, 1]],
+      [-0.35754847096709713, [2, 3, 1]],
+      [1.4301938838683885, [2, 1, 3]],
+      [0.8192464664112216, [0, 5, 1]],
+      [-1.0660035817780522, [0, 3, 3]]
+    ],
+    -2: [
+      [0.27308215547040715, [5, 1, 0]],
+      [0.26650089544451305, [3, 3, 0]],
+      [-0.9534625892455924, [3, 1, 2]],
+      [0.27308215547040715, [1, 5, 0]],
+      [-0.9534625892455924, [1, 3, 2]],
+      [1.4564381625088383, [1, 1, 4]]
+    ],
+    -1: [
+      [0.2878538665448989, [4, 1, 1]],
+      [0.3768891807222045, [2, 3, 1]],
+      [-0.753778361444409, [2, 1, 3]],
+      [0.8635615996346968, [0, 5, 1]],
+      [-1.6854996561581053, [0, 3, 3]],
+      [1.381698559415515, [0, 1, 5]]
+    ],
+    0: [
+      [-0.3125, [6, 0, 0]],
+      [-0.1631978024584667, [4, 2, 0]],
+      [0.9791868147508004, [4, 0, 2]],
+      [-0.1631978024584667, [2, 4, 0]],
+      [0.5733530903673287, [2, 2, 2]],
+      [-1.3055824196677337, [2, 0, 4]],
+      [-0.3125, [0, 6, 0]],
+      [0.9791868147508004, [0, 4, 2]],
+      [-1.3055824196677337, [0, 2, 4]],
+      [1.0, [0, 0, 6]]
+    ],
+    1: [
+      [0.8635615996346968, [5, 0, 1]],
+      [0.3768891807222045, [3, 2, 1]],
+      [-1.6854996561581053, [3, 0, 3]],
+      [0.2878538665448989, [1, 4, 1]],
+      [-0.753778361444409, [1, 2, 3]],
+      [1.381698559415515, [1, 0, 5]]
+    ],
+    2: [
+      [0.45285552331841994, [6, 0, 0]],
+      [0.0788320279858614, [4, 2, 0]],
+      [-1.2613124477737825, [4, 0, 2]],
+      [-0.0788320279858614, [2, 4, 0]],
+      [1.2613124477737825, [2, 0, 4]],
+      [-0.45285552331841994, [0, 6, 0]],
+      [1.2613124477737825, [0, 4, 2]],
+      [-1.2613124477737825, [0, 2, 4]]
+    ],
+    3: [
+      [-0.8192464664112216, [5, 0, 1]],
+      [0.35754847096709713, [3, 2, 1]],
+      [1.0660035817780522, [3, 0, 3]],
+      [0.8192464664112216, [1, 4, 1]],
+      [-1.4301938838683885, [1, 2, 3]]
+    ],
+    4: [
+      [-0.49607837082461076, [6, 0, 0]],
+      [0.4317807998173484, [4, 2, 0]],
+      [0.8635615996346968, [4, 0, 2]],
+      [0.4317807998173484, [2, 4, 0]],
+      [-1.5169496905422948, [2, 2, 2]],
+      [-0.49607837082461076, [0, 6, 0]],
+      [0.8635615996346968, [0, 4, 2]]
+    ],
+    5: [
+      [0.701560760020114, [5, 0, 1]],
+      [-1.5309310892394863, [3, 2, 1]],
+      [1.1692679333668567, [1, 4, 1]]
+    ],
+    6: [
+      [0.6716932893813962, [6, 0, 0]],
+      [-1.7539019000502851, [4, 2, 0]],
+      [1.7539019000502851, [2, 4, 0]],
+      [-0.6716932893813962, [0, 6, 0]]
+    ]
+  }
+}
\ No newline at end of file
diff --git a/tests/test_cgf.py b/tests/test_cgf.py
index df47099..a379e18 100644
--- a/tests/test_cgf.py
+++ b/tests/test_cgf.py
@@ -1,5 +1,5 @@
 import unittest
-from pyqint import PyQInt, Molecule
+from pyqint import PyQInt, Molecule, cgf
 from copy import deepcopy
 import numpy as np
 import os
@@ -67,5 +67,24 @@ def testPlotGrid(self):
         ans = np.load(os.path.join(os.path.dirname(__file__), 'results', 'h2o_orb_1b2.npy'))
         np.testing.assert_almost_equal(res, ans, 6)
 
+    def testSphericalHarmonicsOnSite(self):
+        """
+        Check if the overlap matrix of all spherical harmonics up to l=6 is the identity matrix
+        """
+        basis_functions = []
+        p0 = [0.0, 0.0, 0.0]
+        for l in range(7):
+            for m in range(-l, l+1):
+                orb = cgf(p0)
+                orb.add_spherical_gto(1.0, 1.0, l, m)
+                basis_functions.append(orb)
+        # build overlap matrix
+        om = np.zeros((len(basis_functions), len(basis_functions)))
+        integrator = PyQInt()
+        for i,orb1 in enumerate(basis_functions):
+            for j,orb2 in enumerate(basis_functions):
+                om[i,j] = integrator.overlap(orb1, orb2)
+        np.testing.assert_almost_equal(om, np.eye(om.shape[0]), 6)
+
 if __name__ == '__main__':
     unittest.main()