Evolved Indexing Programs

If N-TREOR does not find satisfactory results in the default run, it will repeat the unit cell search with wider tolerance limits. If still no solution is found, the maximum (h,k,l) Miller indices of the orthorhombic and monoclinic base lines are increased, and correspondingly the tolerance limits are narrowed to 50% of the default value to avoid the generation of a large number of wrong large unit cells. 

If the maximum observed d value is greater than 10 A, the largest cell volume and axis length investigated by N-TREOR are set to 4000 A and 35 A, respectively (the default values in TREOR are 2000 A and 25 A, respectively). 

Monoclinic solutions are checked for possible rhombohedral symmetry. If the symmetry is likely to be rhombohedral N-TREOR calculates the possible hexagonal axes. 

A modified de Wolff figure of merit 20 has been introduced  

If the selected cell has M 20 (= M20) 20 for triclinic crystal systems, or M20 30 i.e., M20 10) for monoclinic or higher symmetry crystal systems, it will be automatically refined by PI RUM, originally an interactive program, suitably modified to perform the automatic refinement of the unit-cell parameters. If more than 25 observed lines are available, the first 25 lines will be used for finding the cell, while all the lines will be involved in the refinement step. At the end of the PI RUM refinement a statistical study of the index parity of the assigned reflections is performed to detect the presence of doubled axes or of additional lattice points (A-, B-, C-, I-, R- or F-centred cell). If one of the index parity conditions is verified, an additional refinement is performed taking into account this information. 

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This property index offers a powerful means to improve the generation of complementary ligands. Over time, builder-type programs evolve compounds with... 

If we now introduce a new vector Y, a new global indexing scheme evolves for the purpose of programming as... 

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