Fixed xtb multiplicity for multiplicities other than 1

Author: RaphaelRobidas

ccinput/packages/xtb.py

@@ -97,7 +97,8 @@ def handle_parameters(self):
             self.main_command += f"--chrg {self.calc.charge} "
 
         if self.calc.multiplicity != 1:
-            self.main_command += f"--uhf {self.calc.multiplicity} "
+            # uhf is the number of unpaired electrons
+            self.main_command += f"--uhf {self.calc.multiplicity-1} "
 
     def handle_constraints_scan(self):
         if len(self.calc.constraints) == 0:

ccinput/tests/test_xtb.py

@@ -43,7 +43,7 @@ def test_sp_multiplicity(self):
 
         xtb = self.generate_calculation(**params)
 
-        REF = "xtb Cl.xyz --uhf 2"
+        REF = "xtb Cl.xyz --uhf 1"
 
         self.assertTrue(self.is_equivalent(REF, xtb.command))
         self.assertTrue(self.is_equivalent("", xtb.input_file))
@@ -59,7 +59,7 @@ def test_sp_charge_multiplicity(self):
 
         xtb = self.generate_calculation(**params)
 
-        REF = "xtb Cl.xyz --chrg -1 --uhf 3"
+        REF = "xtb Cl.xyz --chrg -1 --uhf 2"
 
         self.assertTrue(self.is_equivalent(REF, xtb.command))
         self.assertTrue(self.is_equivalent("", xtb.input_file))