THE CHEMISTRY OF THE SUPERHEAVY ELEMENTS .1. PSEUDOPOTENTIALS FOR 111AND 112 AND RELATIVISTIC COUPLED-CLUSTER CALCULATIONS FOR (112)H-2, AND (112)F-4(, (112)F)

One- and two-component (spin-orbit coupled) relativistic and nonrelati vistic energy adjusted pseudopotentials and basis sets for the element s 111 and 112 are presented. Calculations on the positively charged mo nohydride of the recently discovered superheavy element 112 are report ed. Electron correlation is treated at the multireference configuratio n interaction and coupled cluster level and fine structure effects are derived from a single-reference configuration interaction treatment. Relativistic effects decrease the (112H+ bond distance by 0.41 Angstro m. This bond contraction is similar to the one calculated recently for (111)H [Chem. Phys. Lett. 250, 461 (1996)]. As a result the bond dist ance of (112H+ (1.52 Angstrom) is predicted to be smaller compared to those of the hydrides of the lighter congeners HgH+ (1.59 Angstrom), C dH+ (1.60 Angstrom) and similar to that of ZnH+ (1.52 Angstrom). We pr edict that (112H+ is the most stable hydride in the Group 12 series du e to relativistic effects. As in the case of (111)H the relativistic i ncrease of the stretching force constant is quite large, from 1.5 to 4 .3 mdyn/Angstrom at the coupled cluster level. The trend in the;dipole polarizabilities of the Group 12 elements is discussed. Relativistic and electron correlation effects are nonadditive and due to the relati vistic its contraction (n = 7 for 112), correlation effects out of the (n - 1)d core are more important at the relativistic than the nonrela tivistic level. We also,show evidence that element 112 behaves like a typical transition element, and as a consequence. the high oxidation s tate +4 in element 112 might be accessible. (C) 1997 American Institut e of Physics.