Table 2. Results of quantum refinements of the crystal structure with PDB code 6cdk with different values of the weight factor w _A and the occupancies, showing the R _free and R _work factors and the RSZD score of the P-cluster (the maximum value for the Fe and S atoms in the P-cluster in the two conformations), as well as the strain energy of the QM system.

The first line shows the results for the original crystal structure and the second line shows the results for a refinement in which no QM or MM data are used for the P-cluster.

	Occupancies					Strain energy (kJ mol−1)
w A	P1+	P2+	R free	R work	RSZD	P1+	P2+
6cdk	1.0	0.0	0.2581	0.2118	2.6	1406.4
No-MM	1.0	0.0	0.2577	0.2116	5.4	1159.9
0.0	0.5	0.5	0.2588	0.2049	2.5	0.0	0.0
0.1	0.5	0.5	0.2585	0.2049	2.2	0.2	0.2
0.3	0.5	0.5	0.2588	0.2049	1.4	1.5	1.2
1.0	0.5	0.5	0.2583	0.2038	1.7	7.6	6.8
3.7	0.5	0.5	0.2586	0.2046	1.6	39.1	32.5
10.0	0.5	0.5	0.2577	0.2050	1.5	109.4	92.6
30.0	0.5	0.5	0.2579	0.2051	2.5	222.0	262.7
100.0	0.5	0.5	0.2578	0.2058	1.8	542.0	667.0
1.0	0.4	0.6	0.2584	0.2043	1.5	3.8	9.5
1.0	0.5	0.5	0.2583	0.2038	1.7	7.6	6.8
1.0	0.6	0.4	0.2589	0.2044	2.5	11.8	4.3
10.0	0.4	0.6	0.2578	0.2046	2.0	82.9	103.7
10.0	0.5	0.5	0.2577	0.2050	1.5	109.4	92.6
10.0	0.6	0.4	0.2578	0.2052	2.4	131.7	81.4