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Electronic structure of heavy-element oxides and fluorides: XANES LIII spectroscopy and DFT calculations
ARTICLE IN PRESS
Nuclear Instruments and Methods in Physics Research A 575 (2007) 159–161 www.elsevier.com/locate/nima
Electronic structure of heavy-element oxides and fluorides: XANES LIII spectroscopy and DFT calculations S.P. Gabudaa,, S.G. Kozlovaa,b, V.A. Slepkova, S.B. Erenburga, N.V. Bauska a
A.V. Nikolaev Institute of Inorganic Chemistry SB RAS, 630090 Novosibirsk, Russia b G.K. Boreskov Institute of Catalysis SB RAS, 630090 Novosibirsk, Russia Available online 13 January 2007
Abstract XANES LIII spectra of series Tl, Pb and Bi compounds are studied. The data of DFT–ZORA calculations are in satisfactory agreement with the results of XANES spectroscopy of heavy-element fluorides and oxides. The fine structure of LIII absorption near edge for Tl3+, Pb4+ and Bi5+ ions is associated with transitions to the atomic 6s1/2, 6p1/2 (relativistic allowed) and 6d–7s terms. The ‘‘superfluous’’ lines observed in XANES spectra of Tl+, Pb2+ and Bi3+ oxides and fluorides are associated with the mix of 6s1/2 and 6p3/2 states of heavy 6s2 ions. r 2007 Elsevier B.V. All rights reserved. PACS: 82 Keywords: Heavy-element compounds; LIII XANES; Vibronic interaction; Second-order Jahn–Teller effect; Electronic structure; DFT calculation
1. Introduction High sensitivity of XANES LIII spectra to the chemical form of Hg2+ compounds was revealed recently [1]. Here we report the same sensitivity of the XANES LIII spectra of different compounds of Tl3+, Pb4+ and Bi5+ ions isoelectronic to Hg2+. We also studied electronic structure of Tl+, Pb2+, and Bi3+ ions in different compounds by analyzing their X-ray absorption near-edge (XANES) fine structure. The measurement results were compared with density functional theory (DFT) calculations data. 2. Experimental The XANES experiments were conducted at the EXAFS station of Synchrotron Radiation Center, Budker Institute of Nuclear Physics (Novosibirsk), on the VEPP-3 storage ring [2]. In measurements, the storage ring operated at the energy of 2.00 GeV and current of 50–100 mA. An ionization chamber filled with Ar/He was used as a Corresponding author. Tel.: +3832 3307531.
E-mail address: [email protected] (S.P. Gabuda). 0168-9002/$ - see front matter r 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2007.01.049
monitoring detector. A mono block slit silicon single crystal ({1 1 1} plane) was used as a double-crystal monochromator. The transmission spectra were recorded for samples pressed with an inert filler (cellulose). Fine structure of the spectra is more clearly seen in the second derivatives of the X-ray absorption L(III)-edge curves for lead compounds (see curves in Figs. 1–3). The bTlF was prepared by dissolving Tl2CO3 in 40% hydrofluoric acid (HF) in a platinum crucible; then the solution was evaporated to dryness at 250 1C [3]. The preparation and analysis of the a-PbO, b-PbO, and b-PbO2 samples (rutile structure) is described in Ref. [2], the synthesis and properties of the cubic mixed-valence BiO2 ( ¼ BiIIIBiVO4) oxide with fluorite structure (CaF2) are described in Ref. [2], and the a-Bi2O3 oxide was reagent grade. The BiOCl compound (reagent grade) and the PbClF compound obtained by interacting equimolar amounts of Pb(NO3)2, NH4Cl, and NH4F in an aqueous solution (both are structurally close to a-PbO) were also studied for comparison. Chemical analysis of the samples confirms the composition, and the impurity concentration does not exceed 0.1%. Metallic thallium, lead, and bismuth were used as reference.
ARTICLE IN PRESS S.P. Gabuda et al. / Nuclear Instruments and Methods in Physics Research A 575 (2007) 159–161
160
d* Bi oxogalate
6p1/2 Pb3O4
αPbO
Bi(Hcit) PbO2
6p1/2
d2A/dE2
6s1/2
d2A/dE2
Bi oxosalicilate
βPbO
6p1/2
d*
6s1/2
BiO2
6p1/2 6s1/2
PbS
αBi2O3
6p1/2
6p1/2 PbFCl
BiOCl
6p1/2 -30
-20
-10
0
6p1/2
10 ΔE, eV
20
30
40
-30
Fig. 1. XANES Pb LIII spectra (the second derivatives) of power samples. The vertical line is the assumed absorption edge energy. The little vertical lines indicate the DFT calculated components of fine structure, related to transitions from 2p3/2 state to the states 6s1/2 and 6p1/2.
d*
βTlF
d2A/dE2
6p1/2
Tl2O3
6s1/2
Tl2SO4
6p1/2
-20
-10
0
10
20
-10
0
10 ΔE, eV
20
30
40
Fig. 3. XANES Bi LIII spectra (the second derivatives) of power samples. The vertical line is the assumed absorption edge energy. The little vertical lines indicate the DFT calculated components of fine structure, related to transitions from 2p3/2 state to the states 6s1/2 and 6p1/2.
Table 1 Computed differences DE between energy 6s1/2, 6p1/2, 6d5/2, and 7s1/2 levels relative to 2p3/2 level referenced in eV
6p1/2
-30
-20
30
40
ΔE, eV Fig. 2. XANES Tl LIII spectra (the second derivatives) of power samples. The vertical line is the assumed absorption edge energy. The little vertical lines indicate the DFT calculated components of fine structure, related to transitions from 2p3/2 state to the states 6s1/2 and 6p1/2.
3. Calculations All calculations were performed by the DFT method using the ADF program package [4]. Spin-restricted DFT were carried out using the ADF2003 code. The localexchange VWN correlation potential was used for the local density approximation (LDA), Becke’s nonlocal corrections to the exchange energy, and Perdew’s nonlocal corrections to the correlation energy were added. The zeroth-order relativistic approximation (ZORA) method was used to account for the full relativistic effects. The STO basic set without core potentials was used for all atoms (ADF2003/ZORA/T2ZP) [4].
Term
6s1/2
6p1/2
6d3/2
6d5/2
7s1/2
Tl3+ Tl+ Tl0 Pb4+ Pb2+ Pb0 Bi5+ Bi3+ Bi0
12523.4 Occupied Occupied 12899.1 Occupied Occupied 13281.1 Occupied Occupied
12532.3 12527.4 12526.1 12909.4 12903.9 Occupied 13292.8 13286.8 Occupied
12546.7 12540.1 12538.9 12925.6 12915.6 12908.9 13312.1 13301.6 13292.0
12547.2 12540.6 12539.4 12926.0 12915.9 12909.0 13312.7 13301.9 13284.2
12544.6 12534.1 12531.0 12926.3 12915.1 12907.3 13314.1 13301.5 13290.4
4. Confrontation of experimental and calculated data Electron energy levels for thallium (Tl0, Tl+, Tl3+), lead (Pb0, Pb2+, Pb4+), and bismuth (Bi0, Bi3+, Bi5+) of various oxidation degrees were computed (Table 1). The computed energies were compared with the tabulated XANES LIII energies of metallic Tl0, Pb0, and Bi0 absorption edge corresponding to the allowed 2p3/26d5/2 and 2p3/2-7s1/2 transitions: Tl0L(III) ¼ 12.657 keV, Pb0L(III) ¼ 13.034 keV, Bi0L(III) ¼ 13.418 keV [5]. The computed energies (mean values of 2p3/2-6d5/2 and 2p3/27s1/2 transitions for atoms, Table 1) are 12.537, 12.909, and 13.286 keV, respectively, which is in direct proportion to the tabulated energies with a systematic deviation of 126 eV (or 1%). The directly proportional dependence suggests that the obtained data can be used for studying electron transitions. Comparison of computed transitions and experimental data for Tl+, Tl3+, Pb2+, Pb4+, Bi3+, Bi5+ assumed that the maximum absorption value in XANES-spectra of LIII series is the absorption edge corresponding to 2p3/2 to
ARTICLE IN PRESS S.P. Gabuda et al. / Nuclear Instruments and Methods in Physics Research A 575 (2007) 159–161
6d5/2, 6d3/2, and 7s1/2 (average d* ¼ /6d5/2,6d3/2,7s1/2S) transitions with possible 2p3/2-6s1/2 and 2p3/2-6p1/2 transitions for lower energies relative to the absorption edge. Note that characteristic difference computed between 2p3/2-6s1/2 and 2p3/2-6p1/2 transitions is 10 eV for all ions of higher oxidation degrees. Figs. 1–3 show experimental XANES LIII spectra. The oxides Tl2O3 , PbO2 and BiO2 show a well-marked nearedge structure for Tl3+, Pb4+ and Bi5+ ions (electron configuration 5d106s06p0). In each case, the lowest in energy absorption line should be attributed to the allowed electron dipolar transition from 2p3/2 state to the lowest unoccupied state 6s1/2. Second steps in each of LIII spectra of Tl3+, Pb4+ and Bi5+ ions are shifted in 10 eV to higher energy. Reasoning from DFT calculations (see Table 1), the observed second steps can be related to electron 2p3/2-6p1/2 excitations corresponding to dipolar j–j transition in heavy-atom (relativistic) systems governed by selection rule Dj ¼ 71 [6]. Similar explanation may be valid also for Tl+ and Pb2+ ions (electron configuration 5d106s26p0) in Tl2SO4, PbFCl, and PbS where the 6p1/2 level is not occupied. Taking into consideration the same relativistic selection rule Dj ¼ 1, the lowest energy in absorption line may be related in this case to electron dipolar excitations 2p3/2-6p1/2 forbidden in non-relativistic systems. Another peculiarity of discussed XANES LIII-spectra are the ‘‘superfluous’’ lines, found in b-TlF, a- and b-PbO, Pb3O4, BiOCl, Bi2O3, Bi-citrate, Bi-oxogallate, and Bioxosalicillate. Surprising is the fact that lowest energy in absorption line of Tl+, Pb2+ and Bi3+ ions in these compounds is nearly the same as energies of 2p3/2-6s1/2 transitions observed for Tl3+, Pb4+ and Bi5+ ions. This observation is in drastic contradiction with the fact that the 6s2 state is occupied in Tl+, Pb2+ and Bi3+ ions. As the ‘‘superfluous’’ lines in XANES LIII-spectra are wellmarked in the low-symmetry binary oxides a- and b-PbO, Pb3O4, Bi2O3, and not observed in PbS of NaCl structure type (Fig. 1), one is inclined to think that symmetry lowering may be the reason for additional absorption in above-listed compounds. However, this conclusion does not correlate with experimental XANES LIII-spectra of series of low-symmetry compounds PbFCl, Tl2SO4, and of organic Bi-complexes (Figs. 1–3) where ‘‘superfluous’’ lines also are not shown. The explanation may be related to the pseudo-degeneration of Tl+, Pb2+ and Bi3+ electronic ground state, and to
161
the influence of the second-order Jahn–Teller effect on the symmetry lowering in the discussed compounds [7]. In particular, the starting high (Oh) symmetry of Tl+ and Pb2+ local site in b-TlF, and b-PbO (of distorted NaCl types) may be broken due to the pseudo-degeneration of electronic ground state related to the mix of populated 6s1/2 and unpopulated 6p3/2 states caused by the influence of strong crystal field of F and O2 ligands. Perhaps one can concede that crystal fields generated by S2 ions in PbS, [SO4]2 in Tl2SO4, F and Cl in PbFCl, and organic ligands in Bi-complexes are not strong enough to cause the mix of 6s1/2 and 6p3/2 states of Tl+, Pb2+ and Bi3+in these compounds, so there is no ‘‘superfluous’’ lines in their XANES LIII spectra. 5. Conclusions The data of DFT–ZORA calculations are in satisfactory agreement with the results of XANES spectroscopy of heavy-element fluorides and oxides. The fine structure of L(III) near-edge absorption of Tl3+, Pb4+ and Bi5+ ions is associated with the transitions to the atomic 6s1/2, 6p1/2 (relativistic allowed) and 6d–7s terms. The ‘‘superfluous’’ lines found in XANES spectra of oxides and fluorides of Tl+, Pb2+ and Bi3+ are related to the mix of 6s1/2 and 6p3/2 states of heavy 6s2 ions. Acknowledgment This work was supported by RFBR (Grant no. 05-0332263). References [1] H.H. Harris, I.J. Pickering, G.N. George, Science 301 (5637) (2003) 1203. [2] S.P. Gabuda, S.G. Kozlova, S.B. Erenburg, N.V. Bausk, R.L. Davidovich, V.V. Zyryanov, Yu.M. Yukhin, JETP Lett. 76 (1) (2002) 50. [3] S.P. Gabuda, S.G. Kozlova, R.L. Davidovich, Chem. Phys. Lett. 263 (1996) 253. [4] Amsterdam Density Functional (ADF) program, Release 2003.02; Vrije Universteit, Amsterdam, The Netherlands, 2003. [5] XAFS Database International XAFS Society. /http://ixs.csrri.iit.edu/ database/S /http://www.csrri.iit.edu/periodic-table.htmlS. [6] A. Sommerfeld, Atombau und Spectral Linien, F. Vieweg & Sons, Braunschweig, 1951 1 Band (Chapter 4, n. 6). [7] I.B. Bersuker, The Jahn–Teller effect and vibronic interactions in modern chemistry, Plenum, NY, 1984.
Nuclear Instruments and Methods in Physics Research A 575 (2007) 159–161 www.elsevier.com/locate/nima
Electronic structure of heavy-element oxides and fluorides: XANES LIII spectroscopy and DFT calculations S.P. Gabudaa,, S.G. Kozlovaa,b, V.A. Slepkova, S.B. Erenburga, N.V. Bauska a
A.V. Nikolaev Institute of Inorganic Chemistry SB RAS, 630090 Novosibirsk, Russia b G.K. Boreskov Institute of Catalysis SB RAS, 630090 Novosibirsk, Russia Available online 13 January 2007
Abstract XANES LIII spectra of series Tl, Pb and Bi compounds are studied. The data of DFT–ZORA calculations are in satisfactory agreement with the results of XANES spectroscopy of heavy-element fluorides and oxides. The fine structure of LIII absorption near edge for Tl3+, Pb4+ and Bi5+ ions is associated with transitions to the atomic 6s1/2, 6p1/2 (relativistic allowed) and 6d–7s terms. The ‘‘superfluous’’ lines observed in XANES spectra of Tl+, Pb2+ and Bi3+ oxides and fluorides are associated with the mix of 6s1/2 and 6p3/2 states of heavy 6s2 ions. r 2007 Elsevier B.V. All rights reserved. PACS: 82 Keywords: Heavy-element compounds; LIII XANES; Vibronic interaction; Second-order Jahn–Teller effect; Electronic structure; DFT calculation
1. Introduction High sensitivity of XANES LIII spectra to the chemical form of Hg2+ compounds was revealed recently [1]. Here we report the same sensitivity of the XANES LIII spectra of different compounds of Tl3+, Pb4+ and Bi5+ ions isoelectronic to Hg2+. We also studied electronic structure of Tl+, Pb2+, and Bi3+ ions in different compounds by analyzing their X-ray absorption near-edge (XANES) fine structure. The measurement results were compared with density functional theory (DFT) calculations data. 2. Experimental The XANES experiments were conducted at the EXAFS station of Synchrotron Radiation Center, Budker Institute of Nuclear Physics (Novosibirsk), on the VEPP-3 storage ring [2]. In measurements, the storage ring operated at the energy of 2.00 GeV and current of 50–100 mA. An ionization chamber filled with Ar/He was used as a Corresponding author. Tel.: +3832 3307531.
E-mail address: [email protected] (S.P. Gabuda). 0168-9002/$ - see front matter r 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2007.01.049
monitoring detector. A mono block slit silicon single crystal ({1 1 1} plane) was used as a double-crystal monochromator. The transmission spectra were recorded for samples pressed with an inert filler (cellulose). Fine structure of the spectra is more clearly seen in the second derivatives of the X-ray absorption L(III)-edge curves for lead compounds (see curves in Figs. 1–3). The bTlF was prepared by dissolving Tl2CO3 in 40% hydrofluoric acid (HF) in a platinum crucible; then the solution was evaporated to dryness at 250 1C [3]. The preparation and analysis of the a-PbO, b-PbO, and b-PbO2 samples (rutile structure) is described in Ref. [2], the synthesis and properties of the cubic mixed-valence BiO2 ( ¼ BiIIIBiVO4) oxide with fluorite structure (CaF2) are described in Ref. [2], and the a-Bi2O3 oxide was reagent grade. The BiOCl compound (reagent grade) and the PbClF compound obtained by interacting equimolar amounts of Pb(NO3)2, NH4Cl, and NH4F in an aqueous solution (both are structurally close to a-PbO) were also studied for comparison. Chemical analysis of the samples confirms the composition, and the impurity concentration does not exceed 0.1%. Metallic thallium, lead, and bismuth were used as reference.
ARTICLE IN PRESS S.P. Gabuda et al. / Nuclear Instruments and Methods in Physics Research A 575 (2007) 159–161
160
d* Bi oxogalate
6p1/2 Pb3O4
αPbO
Bi(Hcit) PbO2
6p1/2
d2A/dE2
6s1/2
d2A/dE2
Bi oxosalicilate
βPbO
6p1/2
d*
6s1/2
BiO2
6p1/2 6s1/2
PbS
αBi2O3
6p1/2
6p1/2 PbFCl
BiOCl
6p1/2 -30
-20
-10
0
6p1/2
10 ΔE, eV
20
30
40
-30
Fig. 1. XANES Pb LIII spectra (the second derivatives) of power samples. The vertical line is the assumed absorption edge energy. The little vertical lines indicate the DFT calculated components of fine structure, related to transitions from 2p3/2 state to the states 6s1/2 and 6p1/2.
d*
βTlF
d2A/dE2
6p1/2
Tl2O3
6s1/2
Tl2SO4
6p1/2
-20
-10
0
10
20
-10
0
10 ΔE, eV
20
30
40
Fig. 3. XANES Bi LIII spectra (the second derivatives) of power samples. The vertical line is the assumed absorption edge energy. The little vertical lines indicate the DFT calculated components of fine structure, related to transitions from 2p3/2 state to the states 6s1/2 and 6p1/2.
Table 1 Computed differences DE between energy 6s1/2, 6p1/2, 6d5/2, and 7s1/2 levels relative to 2p3/2 level referenced in eV
6p1/2
-30
-20
30
40
ΔE, eV Fig. 2. XANES Tl LIII spectra (the second derivatives) of power samples. The vertical line is the assumed absorption edge energy. The little vertical lines indicate the DFT calculated components of fine structure, related to transitions from 2p3/2 state to the states 6s1/2 and 6p1/2.
3. Calculations All calculations were performed by the DFT method using the ADF program package [4]. Spin-restricted DFT were carried out using the ADF2003 code. The localexchange VWN correlation potential was used for the local density approximation (LDA), Becke’s nonlocal corrections to the exchange energy, and Perdew’s nonlocal corrections to the correlation energy were added. The zeroth-order relativistic approximation (ZORA) method was used to account for the full relativistic effects. The STO basic set without core potentials was used for all atoms (ADF2003/ZORA/T2ZP) [4].
Term
6s1/2
6p1/2
6d3/2
6d5/2
7s1/2
Tl3+ Tl+ Tl0 Pb4+ Pb2+ Pb0 Bi5+ Bi3+ Bi0
12523.4 Occupied Occupied 12899.1 Occupied Occupied 13281.1 Occupied Occupied
12532.3 12527.4 12526.1 12909.4 12903.9 Occupied 13292.8 13286.8 Occupied
12546.7 12540.1 12538.9 12925.6 12915.6 12908.9 13312.1 13301.6 13292.0
12547.2 12540.6 12539.4 12926.0 12915.9 12909.0 13312.7 13301.9 13284.2
12544.6 12534.1 12531.0 12926.3 12915.1 12907.3 13314.1 13301.5 13290.4
4. Confrontation of experimental and calculated data Electron energy levels for thallium (Tl0, Tl+, Tl3+), lead (Pb0, Pb2+, Pb4+), and bismuth (Bi0, Bi3+, Bi5+) of various oxidation degrees were computed (Table 1). The computed energies were compared with the tabulated XANES LIII energies of metallic Tl0, Pb0, and Bi0 absorption edge corresponding to the allowed 2p3/26d5/2 and 2p3/2-7s1/2 transitions: Tl0L(III) ¼ 12.657 keV, Pb0L(III) ¼ 13.034 keV, Bi0L(III) ¼ 13.418 keV [5]. The computed energies (mean values of 2p3/2-6d5/2 and 2p3/27s1/2 transitions for atoms, Table 1) are 12.537, 12.909, and 13.286 keV, respectively, which is in direct proportion to the tabulated energies with a systematic deviation of 126 eV (or 1%). The directly proportional dependence suggests that the obtained data can be used for studying electron transitions. Comparison of computed transitions and experimental data for Tl+, Tl3+, Pb2+, Pb4+, Bi3+, Bi5+ assumed that the maximum absorption value in XANES-spectra of LIII series is the absorption edge corresponding to 2p3/2 to
ARTICLE IN PRESS S.P. Gabuda et al. / Nuclear Instruments and Methods in Physics Research A 575 (2007) 159–161
6d5/2, 6d3/2, and 7s1/2 (average d* ¼ /6d5/2,6d3/2,7s1/2S) transitions with possible 2p3/2-6s1/2 and 2p3/2-6p1/2 transitions for lower energies relative to the absorption edge. Note that characteristic difference computed between 2p3/2-6s1/2 and 2p3/2-6p1/2 transitions is 10 eV for all ions of higher oxidation degrees. Figs. 1–3 show experimental XANES LIII spectra. The oxides Tl2O3 , PbO2 and BiO2 show a well-marked nearedge structure for Tl3+, Pb4+ and Bi5+ ions (electron configuration 5d106s06p0). In each case, the lowest in energy absorption line should be attributed to the allowed electron dipolar transition from 2p3/2 state to the lowest unoccupied state 6s1/2. Second steps in each of LIII spectra of Tl3+, Pb4+ and Bi5+ ions are shifted in 10 eV to higher energy. Reasoning from DFT calculations (see Table 1), the observed second steps can be related to electron 2p3/2-6p1/2 excitations corresponding to dipolar j–j transition in heavy-atom (relativistic) systems governed by selection rule Dj ¼ 71 [6]. Similar explanation may be valid also for Tl+ and Pb2+ ions (electron configuration 5d106s26p0) in Tl2SO4, PbFCl, and PbS where the 6p1/2 level is not occupied. Taking into consideration the same relativistic selection rule Dj ¼ 1, the lowest energy in absorption line may be related in this case to electron dipolar excitations 2p3/2-6p1/2 forbidden in non-relativistic systems. Another peculiarity of discussed XANES LIII-spectra are the ‘‘superfluous’’ lines, found in b-TlF, a- and b-PbO, Pb3O4, BiOCl, Bi2O3, Bi-citrate, Bi-oxogallate, and Bioxosalicillate. Surprising is the fact that lowest energy in absorption line of Tl+, Pb2+ and Bi3+ ions in these compounds is nearly the same as energies of 2p3/2-6s1/2 transitions observed for Tl3+, Pb4+ and Bi5+ ions. This observation is in drastic contradiction with the fact that the 6s2 state is occupied in Tl+, Pb2+ and Bi3+ ions. As the ‘‘superfluous’’ lines in XANES LIII-spectra are wellmarked in the low-symmetry binary oxides a- and b-PbO, Pb3O4, Bi2O3, and not observed in PbS of NaCl structure type (Fig. 1), one is inclined to think that symmetry lowering may be the reason for additional absorption in above-listed compounds. However, this conclusion does not correlate with experimental XANES LIII-spectra of series of low-symmetry compounds PbFCl, Tl2SO4, and of organic Bi-complexes (Figs. 1–3) where ‘‘superfluous’’ lines also are not shown. The explanation may be related to the pseudo-degeneration of Tl+, Pb2+ and Bi3+ electronic ground state, and to
161
the influence of the second-order Jahn–Teller effect on the symmetry lowering in the discussed compounds [7]. In particular, the starting high (Oh) symmetry of Tl+ and Pb2+ local site in b-TlF, and b-PbO (of distorted NaCl types) may be broken due to the pseudo-degeneration of electronic ground state related to the mix of populated 6s1/2 and unpopulated 6p3/2 states caused by the influence of strong crystal field of F and O2 ligands. Perhaps one can concede that crystal fields generated by S2 ions in PbS, [SO4]2 in Tl2SO4, F and Cl in PbFCl, and organic ligands in Bi-complexes are not strong enough to cause the mix of 6s1/2 and 6p3/2 states of Tl+, Pb2+ and Bi3+in these compounds, so there is no ‘‘superfluous’’ lines in their XANES LIII spectra. 5. Conclusions The data of DFT–ZORA calculations are in satisfactory agreement with the results of XANES spectroscopy of heavy-element fluorides and oxides. The fine structure of L(III) near-edge absorption of Tl3+, Pb4+ and Bi5+ ions is associated with the transitions to the atomic 6s1/2, 6p1/2 (relativistic allowed) and 6d–7s terms. The ‘‘superfluous’’ lines found in XANES spectra of oxides and fluorides of Tl+, Pb2+ and Bi3+ are related to the mix of 6s1/2 and 6p3/2 states of heavy 6s2 ions. Acknowledgment This work was supported by RFBR (Grant no. 05-0332263). References [1] H.H. Harris, I.J. Pickering, G.N. George, Science 301 (5637) (2003) 1203. [2] S.P. Gabuda, S.G. Kozlova, S.B. Erenburg, N.V. Bausk, R.L. Davidovich, V.V. Zyryanov, Yu.M. Yukhin, JETP Lett. 76 (1) (2002) 50. [3] S.P. Gabuda, S.G. Kozlova, R.L. Davidovich, Chem. Phys. Lett. 263 (1996) 253. [4] Amsterdam Density Functional (ADF) program, Release 2003.02; Vrije Universteit, Amsterdam, The Netherlands, 2003. [5] XAFS Database International XAFS Society. /http://ixs.csrri.iit.edu/ database/S /http://www.csrri.iit.edu/periodic-table.htmlS. [6] A. Sommerfeld, Atombau und Spectral Linien, F. Vieweg & Sons, Braunschweig, 1951 1 Band (Chapter 4, n. 6). [7] I.B. Bersuker, The Jahn–Teller effect and vibronic interactions in modern chemistry, Plenum, NY, 1984.