


MOLPRO Basis Query (current), basis=def2QZVPP_OPTNotes:  The "OPTRI" basis sets must be considered as experimental. They were automatically generated to extend the valence space and valenceshellminus1 core space of the orbital basis set. The concrete procedure is described in the thesis of Gerald Knizia (can be obtained online). These were not actually optimized to minimize RI errors; rather, they just fill "holes" in the exponent coverage of the orbital sets, and thereby more or less saturate the region of the valence space covered by the orbital basis sets themselves. The sets are mainy provided as an intermediate solution until better basis sets are developed. Nevertheless, they allow F12 calculations for nearly all elements in the periodic table, and for the cases in which this approach was actually tested (main group elements up to 2nd row), it appeared to work decently. If using them, some validation of the calculations with conventional methods or larger basis sets is strongly recommended.  These OPTRI sets are complementary auxiliary sets: An RI set here can only be used in conjunction with the def2nZVPP orbital set for which it was generated and its singly augmented modification.  Gerald Knizia, 20091120 