Adds UCISD with density-fitting (pyscf#1450)

* Adds support for UCISD with density fitting * Allows RCISD with df in ci.__init__ * Remove trailing whitespaces * Removes unnecessary import
sichaox · Mar 17, 2023 · 737ed93 · 737ed93
1 parent 15920e6
commit 737ed93
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Showing 3 changed files with 39 additions and 8 deletions.
diff --git a/pyscf/ci/__init__.py b/pyscf/ci/__init__.py
@@ -40,7 +40,7 @@ def RCISD(mf, frozen=None, mo_coeff=None, mo_occ=None):
         mf = scf.addons.convert_to_rhf(mf)
 
     if getattr(mf, 'with_df', None):
-        raise NotImplementedError('DF-RCISD')
+        return cisd.RCISD(mf, frozen, mo_coeff, mo_occ)
     else:
         return cisd.RCISD(mf, frozen, mo_coeff, mo_occ)
 RCISD.__doc__ = cisd.RCISD.__doc__
@@ -52,7 +52,7 @@ def UCISD(mf, frozen=None, mo_coeff=None, mo_occ=None):
         mf = scf.addons.convert_to_uhf(mf)
 
     if getattr(mf, 'with_df', None):
-        raise NotImplementedError('DF-UCISD')
+        return ucisd.UCISD(mf, frozen, mo_coeff, mo_occ)
     else:
         return ucisd.UCISD(mf, frozen, mo_coeff, mo_occ)
 UCISD.__doc__ = ucisd.UCISD.__doc__
@@ -73,9 +73,9 @@ def GCISD(mf, frozen=None, mo_coeff=None, mo_occ=None):
 
 def QCISD(mf, frozen=None, mo_coeff=None, mo_occ=None):
     if isinstance(mf, scf.uhf.UHF):
-        raise NotImplementedError 
+        raise NotImplementedError
     elif isinstance(mf, scf.ghf.GHF):
-        raise NotImplementedError 
+        raise NotImplementedError
     else:
         return RQCISD(mf, frozen, mo_coeff, mo_occ)
 QCISD.__doc__ = qcisd.QCISD.__doc__
@@ -93,13 +93,13 @@ def RQCISD(mf, frozen=None, mo_coeff=None, mo_occ=None):
         lib.logger.warn(mf, 'RQCISD method does not support ROHF method. ROHF object '
                         'is converted to UHF object and UQCISD method is called.')
         mf = scf.addons.convert_to_uhf(mf)
-        raise NotImplementedError 
+        raise NotImplementedError
 
     if isinstance(mf, newton_ah._CIAH_SOSCF) or not isinstance(mf, scf.hf.RHF):
         mf = scf.addons.convert_to_rhf(mf)
 
     elif numpy.iscomplexobj(mo_coeff) or numpy.iscomplexobj(mf.mo_coeff):
-        raise NotImplementedError 
+        raise NotImplementedError
 
     else:
         return qcisd.QCISD(mf, frozen, mo_coeff, mo_occ)

diff --git a/pyscf/ci/test/test_ucisd.py b/pyscf/ci/test/test_ucisd.py
@@ -305,6 +305,38 @@ def test_cisdvec_to_amplitudes_overwritten(self):
         t2bb[:] = 1
         self.assertAlmostEqual(abs(vec - vec_orig).max(), 0, 15)
 
+    def test_with_df_s0(self):
+        mol = gto.Mole()
+        mol.atom = [
+            [8 , (0. , 0.     , 0.)],
+            [1 , (0. , -0.757 , 0.587)],
+            [1 , (0. , 0.757  , 0.587)]]
+        mol.basis = '631g'
+        mol.build()
+        rhf = scf.RHF(mol).density_fit(auxbasis='weigend')
+        rhf.conv_tol_grad = 1e-8
+        rhf.kernel()
+        mf = scf.addons.convert_to_uhf(rhf)
+        myci = ci.UCISD(mf)
+        myci.kernel()
+        self.assertAlmostEqual(myci.e_tot, -76.1131374309989, 8)
+
+    def test_with_df_s2(self):
+        mol = gto.Mole()
+        mol.atom = [
+            [8 , (0. , 0.     , 0.)],
+            [1 , (0. , -0.757 , 0.587)],
+            [1 , (0. , 0.757  , 0.587)]]
+        mol.basis = '631g'
+        mol.spin = 2
+        mol.build()
+        mf = scf.UHF(mol).density_fit(auxbasis='weigend')
+        mf.conv_tol_grad = 1e-8
+        mf.kernel()
+        myci = ci.UCISD(mf)
+        myci.kernel()
+        self.assertAlmostEqual(myci.e_tot, -75.8307298990769, 8)
+
 
 if __name__ == "__main__":
     print("Full Tests for UCISD")

diff --git a/pyscf/ci/ucisd.py b/pyscf/ci/ucisd.py
@@ -944,8 +944,7 @@ def ao2mo(self, mo_coeff=None):
             return uccsd._make_eris_incore(self, mo_coeff)
 
         elif getattr(self._scf, 'with_df', None):
-            raise NotImplementedError
-
+            return uccsd._make_df_eris_outcore(self, mo_coeff)
         else:
             return uccsd._make_eris_outcore(self, mo_coeff)