Relativistic effects in molecules: Pseudopotential calculations for PbH+, PbH, PbH2, and PbH4

Nonrelativistic, relativistic, and semiempirical pseudopotentials for the Pb atom have been generated to replace the chemically inert core electrons for investigating the effects of relativity and correlation on molecular properties of PbH+, PbH, PbH2, and PbH4. Spin–orbit effects are taken into account by using a quasirelativistic two-spinor pseudopotential. The relativistic bond contraction is found to be dependent on the Pb(6s) orbital participation in the Pb–H bond (Δrelre : 0.04 Å for PbH+, PbH, and PbH2 and 0.07 Å for PbH4). The calculated and measured values agree excellently [e.g., re (PbH)=1.839 Å; expt. 1.839 Å]. The inert pair effect for the lead hydrides will be discussed.