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Submitted on 1 Jan 1979
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Relativistic molecular calculations of superheavy molecules
A. Rosén, B. Fricke, T. Morovik, D. Ellis
To cite this version:
A. Rosén, B. Fricke, T. Morovik, D. Ellis. Relativistic molecular calculations of superheavy molecules.
Journal de Physique Colloques, 1979, 40 (C4), pp.C4-218-C4-219. �10.1051/jphyscol:1979467�. �jpa-
00218863�
JOURNAL DE PHYSIQUE Colloque C4, supplément au n° 4, Tome 40, avril 1979, page C4-218
Relativistic molecular calculations of superheavy molecules (*)
A. Rosen, B. Fricke (*), T. Morovic (*) and D. E. Ellis (
t f)
Chalmers University of Technology, Goteborg, Sweden
(
+) Gesamthochschule Kassel, D-3500 Kassel, Heinrich-Plett-Str. 40, Germany (
t +) Northwestern University Evanston, 111. 60201, U.S.A.
Résumé. — On étudie la structure électronique des hexafluorures des métaux 6d superlourds au moyen de calculs relativistes Dirac-Slater moléculaires. Les résultats théoriques sont comparés aux calculs et aux expériences effectués sur les séries homologues 4d et 5d. La structure électronique est dominée par le fort couplage spin-orbite qui, pour les éléments superlourds, est du même ordre de grandeur que le champ cristallin pour les électrons de valence. Des valeurs des énergies d'ionisation ont été calculées par la méthode de l'état de transition.
Abstract. — Relativistic molecular calculations within the Dirac-Slater scheme have been used in a study of the electronic structure of 6d-metal superheavy hexafluorides. The theoretical results are compared with calculations and measurements of the homolog 4d- and 5d-metal hexafluorides. Large spin-orbit splitting dominates the electronic structure and even has the same order of magnitude as the crystal-field splitting for the valence electrons for the superheavy molecules. Ionization energies have been calculated using a transition state procedure.
1. Introduction. — In recent years a number of atomic calculations have been carried out in the region of superheavy elements. With sophisticated interpretations of these results one was able to get a first idea of the physical and chemical properties of the still unknown superheavy elements. These results have been reviewed by Hermann [1] and Fricke [2]. Many authors [1-3] also have empha- sized that further development in this field is depen- dent on realistic (which in this case means relativistic) calculations for molecules containing superheavy elements. A better knowledge of their chemical and physical properties is the condition for the successful extraction and identification of possi- bly artificially generated superheavy atoms. Prelimi- nary results are given in this work for (E106) F
6and its 4d and 5d elements analogs MoF
6and WF
6for comparison. We also compare it with the recently presented results [4] for (El 10) F
6the analog of the 5d element PtF
6.
The calculation procedure which is based on the relativistic self-consistent Dirac-Slater model has been reviewed in earlier works and is therefore not presented here [5, 6].
2. Results. — In figure 1 we present the outer electron structure resulting from relativistic calcula- tions of (E106)F
6, WF
6and MoF
6as well as a non-relativistic calculation of MoF
6. The composi- tion and relative ordering of the molecular levels depends on the relative level positions for the consti-
(*) Partially supported by Gesellschaft fur Schwerionenfor- schung, Darmstadt.
Non-rel R e l a t i v i s t i c
,
0- ' Mo F
6' ' M O F
6\NF
6E106 F
6' - 10
t 6" 6*
- 2 0 - 20
* l u ^ g -
e
g ===r=^|t
> 7"
" 1-
^< o
» - A 0 - . « * - ^ j : - - 4 0 en - 8
fe t,
u^ _ /
8"
c ^ ^~- ^
Uj \
-SO - \ 50
\ \
-60 - \ 60
\ \
a' g -. \ 6"
-70 - X 70
\ \
\ \
-80 - \ 60
\
\
\
- 9 0 - \ - "90
\ \ \
\
N 6*
-100 - TOO
Fig. 1. — Energy eigenvalues of the outer electrons for MoF
6,
WF
6and (E106) F
6. Non-relativistic calculation of MoF
6also is included.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1979467
RELATIVISTIC MOLECULAR CALCULATIONS O F S U P E R H E A V Y M O L E C U L E S C4-219
tuent atoms, the crystal-field splitting and covalency effects. The experimental bond length of
have been used ; R,,,., was estimated a s 1.84 A.
Extended calculations [4] of (El 10) F, have shown, that the positions of the levels are very insensitive to changes even of 0.1 A of the relative distance between the metal and the fluor atoms. The splitting of the non-relativistic levels into the relativistic ones has been indicated by using the compatibility rela- tions between the single and double groups.
The main influence o n the position of the levels already is given by the position of the atomic levels [7]. The lowest a,, and t,, levels shown in figure 1 mainly can be described by a n s respective- ly n p level of the heavy atom. The large spin-orbit splitting into the 6- and 8- states can easily be seen.
The next levels mainly originate from the f levels of the central atom and from the atomic fluor 2s level.
For the valence electron levels at about - 10 eV,
a more detailed analysis shows that there is a reordering of the valence levels for (E106) F,, so that a y, level becomes the last occupied states, whereas in all lighter systems this is a y i level.
The first excited states for these molecules (dashed levels in Fig. 1) are the crystal-field split t,, and e, molecular levels derived from the n d atomic level. Experimentally the t,, spin-orbit splitting for the 5d metal hexafluorides has been measured t o be
.=
