add QChem SCF convergence method pseudo-Fractional Occupation Number

custodian/qchem/handlers.py

@@ -385,6 +385,18 @@ def fix_scf(self):
                 self.fix_step.set_scf_algorithm_and_iterations(
                     algorithm="gdm", iterations=self.scf_max_cycles)
                 self.set_scf_initial_guess("core")
+            elif method == "fon":
+                self.fix_step.set_scf_algorithm_and_iterations(
+                    algorithm="diis", iterations=self.scf_max_cycles)
+                self.set_scf_initial_guess("sad")
+                natoms = len(od["molecules"][-1])
+                self.fix_step.params["rem"]["occupations"] = 2
+                self.fix_step.params["rem"]["fon_norb"] = int(natoms * 0.618)
+                self.fix_step.params["rem"]["fon_t_start"] = 300
+                self.fix_step.params["rem"]["fon_t_end"] = 300
+                self.fix_step.params["rem"]["fon_e_thresh"] = 6
+                self.fix_step.set_integral_threshold(14)
+                self.fix_step.set_scf_convergence_threshold(7)
             else:
                 raise ValueError("fix method " + method + " is not supported")
             strategy_text = "<SCF Fix Strategy>"

custodian/qchem/tests/test_handlers.py

@@ -218,6 +218,29 @@ def test_scf_rca(self):
                                         'Molecular charge is not found'],
                              'actions': None})
 
+
+    def test_scf_fon(self):
+        shutil.copyfile(os.path.join(test_dir, "hf_rca_hit_5.inp"),
+                        os.path.join(scr_dir, "hf_rca_hit_5.inp"))
+        shutil.copyfile(os.path.join(test_dir, "hf_rca.out"),
+                        os.path.join(scr_dir, "hf_rca.out"))
+        h = QChemErrorHandler(input_file="hf_rca_hit_5.inp",
+                              output_file="hf_rca.out")
+        has_error = h.check()
+        self.assertTrue(has_error)
+        d = h.correct()
+        self.assertEqual(d, {'errors': ['Bad SCF convergence',
+                                        'Geometry optimization failed',
+                                        'Molecular charge is not found'],
+                             'actions': ['fon']})
+        with open(os.path.join(test_dir, "hf_rca_hit_5_fon.inp")) as f:
+            ref = [line.strip() for line in f.readlines()]
+        with open(os.path.join(scr_dir, "hf_rca_hit_5.inp")) as f:
+            ans = [line.strip() for line in f.readlines()]
+        ans = self._revert_scf_fix_strategy_to_version(ans, fix_version="2.0")
+        self.assertEqual(ref, ans)
+
+
     def test_negative_eigen(self):
         shutil.copyfile(os.path.join(test_dir, "negative_eigen.qcinp"),
                         os.path.join(scr_dir, "negative_eigen.qcinp"))

test_files/qchem/hf_rca_hit_5.inp

@@ -0,0 +1,33 @@
+$comment
+ <SCF Fix Strategy>{
+    "current_method_id": 5, 
+    "methods": [
+        "increase_iter", 
+        "rca_diis", 
+        "gwh", 
+        "gdm", 
+        "rca", 
+        "core+rca",
+        "fon"
+    ],
+    "version": 2.0
+}</SCF Fix Strategy>
+$end
+
+
+$molecule
+ 0  1
+ H           0.00000000        0.00000000       -0.86267400
+ F           0.00000000        0.00000000        0.04381300
+$end
+
+
+$rem
+         jobtype = opt
+        exchange = b3lyp
+           basis = 6-31g*
+  max_scf_cycles = 200
+   scf_algorithm = rca
+       scf_guess = core
+$end
+

test_files/qchem/hf_rca_hit_5_fon.inp

@@ -0,0 +1,40 @@
+$comment
+<SCF Fix Strategy>{
+    "current_method_id": 6, 
+    "methods": [
+        "increase_iter", 
+        "rca_diis", 
+        "gwh", 
+        "gdm", 
+        "rca", 
+        "core+rca", 
+        "fon"
+    ], 
+    "version": 2.0
+}</SCF Fix Strategy>
+$end
+
+
+$molecule
+ 0  1
+ H           0.00000000        0.00000000       -0.86267400
+ F           0.00000000        0.00000000        0.04381300
+$end
+
+
+$rem
+          jobtype = opt
+         exchange = b3lyp
+            basis = 6-31g*
+     fon_e_thresh = 6
+         fon_norb = 1
+        fon_t_end = 300
+      fon_t_start = 300
+   max_scf_cycles = 200
+      occupations = 2
+    scf_algorithm = diis
+  scf_convergence = 7
+        scf_guess = sad
+           thresh = 14
+$end
+