Optimization of extended basis sets and assessment of different theoretical schemes for Pb containing compounds

Extended basis sets for Pb to be used in conjunction with the Stevens et al. (denoted by SKBJ) and the Stuttgart effective core potentials (ECPs) have been optimized. An assessment of different ab initio and density functional procedures showed that all methods based on the use of the SKBJ ECP exaggerate the Pb+ binding enthalpies, which are systematically 35–50 kJ mol−1 larger than those obtained when the Stuttgart ECP is employed. The G96LYP/Stutt method yields values in close agreement with those obtained at the QCISD(T)/Stutt and CCSD(T)/Stutt levels of theory, but at a significantly lower cost. Also the B3LYP/Stutt, the BLYP/Stutt and the MP2/Stutt approaches provide a good compromise between accuracy and computational cost for the calculation of binding enthalpies.