LARGE RELATIVISTIC EFFECTS IN MOLECULAR-PROPERTIES OF THE HYDRIDE OF SUPERHEAVY ELEMENT-111

Relativistic and electron correlation contributions in the hydride of the recently discovered superheavy element 111 were studied using ab-i nitio methods within different relativistic approaches, Relativistic e ffects decrease the (111)H bond distance by 0.42 Angstrom. As a result of this large bond contraction, the bond distance of(111)H (1.51 Angs trom) is comparable to that of the hydride of its lighter congener AuH (1.52 Angstrom), but below that of AgH (1.60 Angstrom). The dissociat ion energy is relativistically increased by approximately 1.2 eV and t he stretching force constant is more than quadrupled from 1.1 mdyn/Ang strom at the nonrelativistic level to 5.0 mdyn/Angstrom at the relativ istic level.