Theoretical predictions of trends in spectroscopic properties of homonuclear dimers and volatility of the 7p elements

Abstract

Fully relativistic density functional theory electronic structure calculations were performed for homonuclear dimers of the 7p elements, 113-118 and their 6p homologs, Tl through Rn. All the dimers of the heaviest elements, with the exception of (118)(2), were found to be weaker bound than their lighter homologs. The difference in the dissociation energy (D(e)) between the 6p and 7p homologs was shown to decrease from group 15 to group 17, with a reversal of the trend in group 18. A remarkable feature is a shift of the maximum in D(e)(M(2)) from group 15 in the third through sixth rows to group 16 in the seventh row. Strong relativistic effects on the 7p atomic orbitals, particularly, their large spin-orbit splitting, were shown to be responsible for these trends. Using the calculated D(e)(M(2)), the sublimation enthalpies, DeltaH(sub), of macroamounts, or formation enthalpies of gaseous atoms, DeltaH(f)(g), of the heaviest elements were estimated using a linear correlation between these quantities in the chemical groups. The newly estimated values are in good agreement with those obtained via a linear extrapolation from the lighter homologs in the groups.

Relativistic electronic structure studies on the heaviest elements

“…All the dimers of group-13 through 17 7 p elements were shown to be weaker bound than their 6 p homologs, with the difference in D e (M 2 ) between them decreasing with a group number and a final reversal of the trend in group 18. The latter finding also agrees with the outcome of RECP calculations [94] (see a comparison of the results in [134]). …”

“…Homonuclear dimers. Having in mind that bonding in M 2 is related to bonding in the solid state of M, a systematic study for the entire series of the 7 p homonuclear dimers and their 6 p homologs was performed using the 4c-DFT method [134]. The obtained D e (M 2 ) are shown in Fig.…”

“…MOs, so that the half-filled shell (with 6 electrons) falls on Bi 2 (see discussions in [134]). Element 114.…”

“…In [134], ΔH sub = ΔH f (g) of the 7 p elements were estimated via a correlation with the calculated D e (M 2 ) in the respective chemical groups. The obtained in this way ΔH f (g) and those predicted via a linear extrapolation in the groups [118] are given in Table 8, in good agreement with each other.…”

Binary and ternary Po-containing molecules relevant for LBE cooled reactors at operating temperature

“…They confirm that the postulated set of Po-molecules is meaningful. theoretical studies on heavy elements focus on fundamental aspects, using a variety of computationally very demanding methods [22,23,24]. The challenges within this respect are twofold: Firstly the introduction of relativistic effects is expected to be important.…”