The recently pu
blished Parametric Method num
ber 7, PM7, is the first semiempirical method to
be successfully tested
by modeling crystal structures and heats of formation of solids. PM7 is thus also capa
ble of producing results of useful accuracy for materials science and constitutes a great improvement over its predecessor, PM6. In this article, we present Sparkle model parameters to
be used with PM7 that allow the prediction of geometries of metal complexes and materials which contain lanthanide trications. Accordingly, we considered the geometries of 224 high-quality crystallographic structures of complexes for the parametrization set and 395 more for the validation of the parametrization for the whole lanthanide series, from La(III) to Lu(III). The average unsigned error for Sparkle/PM7 for the distances
between the metal ion and its coordinating atoms is 0.063 脜 for all lanthanides, ranging from a minimum of 0.052 脜 for T
b(III) to 0.088 脜 for Ce(III), compara
ble to the equivalent errors in the distances predicted
by PM7 for other metals. These distance deviations follow a gamma distri
bution within a 95% level of confidence, signifying that they appear to
be random around a mean, confirming that Sparkle/PM7 is a well-tempered method. We conclude
by carrying out a Sparkle/PM7 full geometry optimization of two spatial groups of the same thulium-containing metal organic framework, with unit cells accommodating 376 atoms, of which 16 are Tm(III) cations; the optimized geometries were in good agreement with the crystallographic ones. These results emphasize the capa
bility of the use of the Sparkle model for the prediction of geometries of compounds containing lanthanide trications within the PM7 semiempirical model, as well as the usefulness of such semiempirical calculations for materials modeling. Sparkle/PM7 is availa
ble in the software package MOPAC2012, at no cost for academics and can
be o
btained from
http://openmopac.net.