First-principles study of electronic
structure of Ce3+ centers in alkaline-
earth fluorides including spin-orbit and
scala...
Introduction
Due to the fast 5d → 4f emission of Ce3+ in the blue and UV spectral
regions cerium-doped compounds(Ce3+ in C...
Calculation details
● We developed a set of utilities for embedded quantum
cluster calculation, including:
– embedding.exe — calculating class...
[1] http://www.chokkan.org/software/liblbfgs/
● We used 2-th order Douglas-Kroll-Hess method to include
scalar relativisti...
Quantum cluster
Point charges, pair
potentials & AIMPs;
geometry opt.
available
Fixed point charges
Ce3+ cubic centre
“Cubic” Ce3+ centre
Due to asymmetric charge localization
geometry optimization brings structure to
the lower symmetry.
Sy...
Ce3+ 4f orbitals (“cubic” centre)
Eu
ε=-0.5351 a.u.
Eu
ε=-0.5351 a.u.
A2u
ε=-0.5351 a.u.
Eu
ε=-0.5334 a.u
Eu
ε=-0.5334 a.u...
Eg
ε=-0.5064 a.u.
Eg
ε=-0.5064 a.u.
B2g
ε=-0.5064 a.u.
B1g
ε=-0.3901 a.u
A1g
ε=-0.3901 a.u
Ce3+ 5d orbitals (“cubic” centr...
CAS states of CaF2:Ce3+
Without spin-orbit coupling With spin-orbit coupling
SF
State
Symm. State energy
(eV)
State energy...
SrF2:CeF8 relaxed «Oh» ci
Energy Levels
Without spin-orbit coupling With spin-orbit coupling
SF
State
State
Energy(a.u)
Re...
Jahn-Teller
induced lines
CaF2:Ce3+ absorption without SOC
SOC induced
lines
CaF2:Ce3+ absorption without Jahn-
Teller relaxation
CaF2:Ce3+ absorption with Jahn-Teller
relaxation
Ce3+ OA lines in CaF2:
Calc.
energy,
cm-1
Oscillator
strength
Expt.
energy
cm-1 [1]
Calc.
energy
cm-1[2]
32698,7 2.2E-02 3...
SrF2:CeF8 «Oh» absorption spectrum
Spectral lines
Transition energy,
cm^-1[calculated]
Oscillator
Strength
Line frequency
...
Ce3+ with interstitial fluorine ion
Atom X, Å Y, Å Z, Å ΔX, Å ΔY, Å ΔZ, Å
CE 1.38 0 0 -0.16 0 0
CA0-CA3 -1.38 0 2.76 -0.03 0 -0.15
CA4 -4.14 0 0 0.16 0 0
FI -...
Atom X, Å Y, Å Z, Å ΔX, Å ΔY, Å ΔZ, Å
CE0 1.47 0 0 -0.09 0 0
SR0-SR3 -1.47 0 2.94 0 0 -0.23
SR4 -4.41 0 0 0.23 0 0
FI -1.4...
CaF2:Ca5CeF13 C4V 4f HF orbitals
Symmetry:c1
Energy:-0.5064 a.u.
Symmetry:c1
Energy:-0.5064 a.u.
Symmetry:c1
Energy:-0.506...
CaF2:Ca5CeF13 C4V 5d HF orbitals
Symmetry:c1
Energy:-0.5064 a.u.
Cubic Notation: dx2-y2
Symmetry:c1
Energy:-0.5064 a.u.
Cu...
CaF2:Ce3+Fi
- absorption
W/o
SOC
With SOC
W/o
SOC
With SOC
SrF2:Ce3+Fi
- absorption
CaF2:Ca5CeF13 C4v absorption spectrum
Spectral lines
Energy, cm-
1
[calculated]
Oscillator
strength
Line
frequency
cm^ -1[...
SrF2:Ce3+Fi
- absorption spectrum
Spectral lines
Transition
energy, cm^-1
[calculated]
Oscillator
strength
Line frequency
...
SrF2:Ce3+ absorption spectrum
Experimental Reference:Cubic and tetragonal
Ce3+ ions in strontium fluoride (E. Radzhabov,
T...
Conclusion
1. We have developed an approach for embedded cluster QM/MM calculations with
MOLCAS quantum chemistry package ...
of 28

Popov eurodim2014

scientific presentation
Published on: Mar 4, 2016
Published in: Science      
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Transcripts - Popov eurodim2014

  • 1. First-principles study of electronic structure of Ce3+ centers in alkaline- earth fluorides including spin-orbit and scalar relativistic effects. N.V. Popov, A.S.Mysovsky, E.A.Radzhabov National Research Irkutsk State Technical University (NR ISTU), Irkutsk, 83 Lermontov street A.P. Vinogradov Institute of Geochemistry SB RAS, Irkutsk, 1a Favorsky St.
  • 2. Introduction Due to the fast 5d → 4f emission of Ce3+ in the blue and UV spectral regions cerium-doped compounds(Ce3+ in CaF2,SrF2) have considerable interest in application of scintillators and solid state lasers. Picture of 4f-5d transitions state depend strongly on the local crystalline environment of the dopant Ce3+, due to the large crystal-field interaction experienced by the 5d electron. Problem Our purpose is to study electronic structure and optical transitions in crystal-defect systems (CaF2, SrF2) using embedding quantum cluster formalism, including scalar and spin-orbit effects.
  • 3. Calculation details
  • 4. ● We developed a set of utilities for embedded quantum cluster calculation, including: – embedding.exe — calculating classical gradient and energies – optimus_lbfgs.exe — “glue” for our classical code and third- party quantum chemistry package, it performs geometry optimization in a combined QM/MM fashion – Pre- and postrpocessing tools, scripts ● As a “calculator” we use Molcas 7.8
  • 5. [1] http://www.chokkan.org/software/liblbfgs/ ● We used 2-th order Douglas-Kroll-Hess method to include scalar relativistic effects ● Basis set - ANO Relativistic core correction full electron basis(B. O. Roos, V. Veryazov and P.-O. Widmark) ● Non-quantum cluster atoms were described by Ab initio model potential (AIMPs) ● For large-scale nonlinear optimization problem we use Limited Memory Broyden-Flebsche-Gordano (aka L-BFGS)[1] ● Restricted Active Space State Interaction (RASSI) for accounting for spin-orbit effects
  • 6. Quantum cluster Point charges, pair potentials & AIMPs; geometry opt. available Fixed point charges
  • 7. Ce3+ cubic centre
  • 8. “Cubic” Ce3+ centre Due to asymmetric charge localization geometry optimization brings structure to the lower symmetry. Symmetry breaks from Oh to D4h! F- Ce3+ CeF8 clusterCaF2 X, Å Y, Å Z, Å 1.38 1.38 1.38 ΔX, Å ΔY, Å ΔZ, Å -0.043 -0.043 0.024 SrF2 X, Å Y, Å Z, Å 1.47 1.47 1.47 ΔX, Å ΔY, Å ΔZ, Å -0.095 -0.095 -0.026
  • 9. Ce3+ 4f orbitals (“cubic” centre) Eu ε=-0.5351 a.u. Eu ε=-0.5351 a.u. A2u ε=-0.5351 a.u. Eu ε=-0.5334 a.u Eu ε=-0.5334 a.u B1u ε=-0.5334 a.u B1u ε=-0.5259 a.u.
  • 10. Eg ε=-0.5064 a.u. Eg ε=-0.5064 a.u. B2g ε=-0.5064 a.u. B1g ε=-0.3901 a.u A1g ε=-0.3901 a.u Ce3+ 5d orbitals (“cubic” centre)
  • 11. CAS states of CaF2:Ce3+ Without spin-orbit coupling With spin-orbit coupling SF State Symm. State energy (eV) State energy (cm-1) 1 Eu 0.00 0.0 2 Eu 0.00 2.3 3 ? 0.02 147.5 4 ? 0.03 258.9 5 Eu 0.04 284.1 6 Eu 0.04 285.9 7 B1u 0.30 2411.3 8 ? 3.91 31526.3 9 ? 4.09 33027.9 10 ? 6.73 54293.5 11 Eg 7.07 57015.5 12 Eg 7.07 57017.3 SF State State energy (eV) State energy (cm-1) 1 0.00 0.0 2 0.02 199.8 3 0.08 617.9 4 0.28 2223.0 5 0.30 2451.6 6 0.31 2476.0 7 0.51 4081.7 8 4.05 32698.7 9 4.24 34199.0 10 6.87 55406.5 11 7.16 57751.4 12 7.32 59010.2 Note: 4f orbitals, 5d orbitals, each SOC state is doubly degenerate
  • 12. SrF2:CeF8 relaxed «Oh» ci Energy Levels Without spin-orbit coupling With spin-orbit coupling SF State State Energy(a.u) Rel lowest level(eV) D:o, cm^(-1) 1 -803.94530534 0.000000 0.000 2 -803.94529314 0.000332 2.676 3 -803.94464855 0.017872 144.148 4 -803.94427790 0.027958 225.497 5 -803.94415992 0.031168 251.389 6 -803.94415282 0.031361 252.947 7 -803.93629335 0.245229 1977.902 8 -803.79439250 4.106547 33121.538 9 -803.78825812 4.273472 34467.880 10 -803.70622350 6.505748 52472.398 11 -803.69535003 6.801630 54858.849 12 -803.69534627 6.801732 54859.675 SF State State Energy(a.u) Rel lowest level(eV) D:o, cm^(-1) 1 -803.95103338 0.000000 0.000 2 -803.95019927 0.022697 183.067 3 -803.94842548 0.070965 572.369 4 -803.94080888 0.278223 2244.018 5 -803.93985982 0.304048 2452.314 6 -803.93976930 0.306511 2472.179 7 -803.93403490 0.462552 3730.736 8 -803.79473876 4.252993 34302.703 9 -803.78861021 4.419760 35647.767 10 -803.70680007 6.645927 53603.017 11 -803.69754226 6.897845 55634.871 12 -803.69188017 7.051918 56877.555
  • 13. Jahn-Teller induced lines CaF2:Ce3+ absorption without SOC
  • 14. SOC induced lines CaF2:Ce3+ absorption without Jahn- Teller relaxation
  • 15. CaF2:Ce3+ absorption with Jahn-Teller relaxation
  • 16. Ce3+ OA lines in CaF2: Calc. energy, cm-1 Oscillator strength Expt. energy cm-1 [1] Calc. energy cm-1[2] 32698,7 2.2E-02 32300 33633 34199,0 3,9E-04 55406,5 2,4E-02 51600 48071 57751,4 2,6E-03 53000 59010,2 1,3E-03 55200 References: [1] L. van Pieterson, FM Reid, RT Wegh, S Soverna, A Meijerink, PRB 65, 045113 (2002) [2]A. Myasnikova, A. Mysovsky, E. Radzhabov, Opt. i Specktr. 114, 445 (2013)
  • 17. SrF2:CeF8 «Oh» absorption spectrum Spectral lines Transition energy, cm^-1[calculated] Oscillator Strength Line frequency cm^ -1[1] 34302.703 1,92E-02 33955.943 34302.703 3,54E-03 35647.767 3,36E-05 35647.767 4,31E-04 53603.017 1,67E-03 46538.192 53603.017 2,10E-02 55634.871 2,24E-03 55634.871 1,74E-04 56877.555 5,99E-04 56877.555 6,06E-04 References: [1]First Principle Calculation of 4fn-4f(n-1) 5d Absorption Spectra of Ce3+ and Pr3+ Ions in Alkaline Earth Fluorides Alexandra Myasnikova, Andrey Mysovsky, and Evgeny Radzhabov Insufficient correlation accounting come from small active space: only one 4f electron for Ce3+ Absorption spectrum
  • 18. Ce3+ with interstitial fluorine ion
  • 19. Atom X, Å Y, Å Z, Å ΔX, Å ΔY, Å ΔZ, Å CE 1.38 0 0 -0.16 0 0 CA0-CA3 -1.38 0 2.76 -0.03 0 -0.15 CA4 -4.14 0 0 0.16 0 0 FI -1.38 0 0 0.04 0 0 Ce CA4 Interstitial Fluorine CA0-CA3 Ce3+Fi - in CaF2
  • 20. Atom X, Å Y, Å Z, Å ΔX, Å ΔY, Å ΔZ, Å CE0 1.47 0 0 -0.09 0 0 SR0-SR3 -1.47 0 2.94 0 0 -0.23 SR4 -4.41 0 0 0.23 0 0 FI -1.47 0 0 0.12 0 0 Ce3+Fi - in SrF2 Ce SR4 Interstitial Fluorine SR0-SR3
  • 21. CaF2:Ca5CeF13 C4V 4f HF orbitals Symmetry:c1 Energy:-0.5064 a.u. Symmetry:c1 Energy:-0.5064 a.u. Symmetry:c1 Energy:-0.5064 a.u. Symmetry:t2u Energy:-0.3901 a.u Symmetry:t2u Energy:-0.3901 a.u. Symmetry:t2u Energy:-0.3901 a.u. Symmetry:t2u Energy:-0.3901 a.u.
  • 22. CaF2:Ca5CeF13 C4V 5d HF orbitals Symmetry:c1 Energy:-0.5064 a.u. Cubic Notation: dx2-y2 Symmetry:c1 Energy:-0.5064 a.u. Cubic Notation:dz2 Symmetry:c1 Energy:-0.5064 a.u. Cubic Notation:dxy Symmetry:t2u Energy:-0.3901 a.u Cubic Notation: dxz Symmetry:t2u Energy:-0.3901 a.u. Cubic Notation: dyz
  • 23. CaF2:Ce3+Fi - absorption W/o SOC With SOC
  • 24. W/o SOC With SOC SrF2:Ce3+Fi - absorption
  • 25. CaF2:Ca5CeF13 C4v absorption spectrum Spectral lines Energy, cm- 1 [calculated] Oscillator strength Line frequency cm^ -1[1] 32986,13 0,00981 32907 32986,13 0,012068 41680,98 0,002818 41457 41680,98 0,00288 53236,06 0,001499 46377 53236,06 0,001527 53536,85 0,009555 47506 53536,85 0,009741 55020,82 0,001747 55020,82 0,002242 [1] Calculations by Alexandra Myasnikova, Andrey Mysovsky, and Evgeny Radzhabov Absorption spectrum
  • 26. SrF2:Ce3+Fi - absorption spectrum Spectral lines Transition energy, cm^-1 [calculated] Oscillator strength Line frequency cm^ -1[1] 35269,89 0,013039 34117 35269,89 0,009742 39762,28 0,000746 40247 39762,28 0,000695 51888 0,002082 46861 51888 0,002113 52522,33 0,005922 47829 52522,33 0,006764 54419,72 0,003892 54419,72 0,004181 References: [1]First Principle Calculation of 4fn-4f(n-1) 5d Absorption Spectra of Ce3+ and Pr3+ Ions in Alkaline Earth Fluorides Alexandra Myasnikova, Andrey Mysovsky, and Evgeny Radzhabov Absorption spectrum
  • 27. SrF2:Ce3+ absorption spectrum Experimental Reference:Cubic and tetragonal Ce3+ ions in strontium fluoride (E. Radzhabov, T. Kurobori) Experimental: Calculated:
  • 28. Conclusion 1. We have developed an approach for embedded cluster QM/MM calculations with MOLCAS quantum chemistry package used for electronic structure calculations. The approach itself is similar to GUESS method (AL Shluger, PV Sushko). 2. This allows to use the strong side of MOLCAS - sophisticated post-SCF and multiconfigurational techniques – for calculations of defects in solids. 3. 4f-5d Ce3+ electronic transitions in CaF2 and SrF2(Oh and C4v centers) were studied using CASPT2 and scalar-relativistic Douglas-Kroll-Hess approach. Spin-orbit coupling was treated with the restrictive active space state interaction (RASSI). 4. It is shown that cubic Ce3+ centers in CaF2 and SrF2 undergoes asymmetric relaxation due to Jahn-Teller effect. Optical absorption spectrum calculated with this asymmetric relaxation demonstrates good agreement with experiment, moreover, allows to explain and identify the absorption lines. 5. Calculated optical absorption for Ce3+ with interstitial fluorine ion shows good agreement with experiment as well.

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