xps chemical shifts calculations: confrontation of...
TRANSCRIPT
Germain VallverduUPPA / IPREM Roscoff, May 21-27, 2016
XPS chemical shifts calculations : confrontation of experimentaland theoretical investigations
Germain VALLVERDU
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM
Roscoff, May 21-27, 2016 – 2/38
OUTL
INE
1 X-Ray Photoemission spectroscopy
2 Computational approach of core level binding energies
3 Application to the study of Li-ion battery materials
Core level calculations on LiPON models
Surface reactivity of layered lithium oxides
4 Conclusion
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM
Roscoff, May 21-27, 2016 – 3/38
OUTL
INE
1 X-Ray Photoemission spectroscopy
2 Computational approach of core level binding energies
3 Application to the study of Li-ion battery materials
4 Conclusion
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 4/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
X-Ray Photoemission Spectroscopy (XPS)Basics of the method
The binding energy (BE) of an electron into a core level iscomputed from the photon energy and the kinetic energy ofthe emitted electron
BE = hν − Ekinet = EcN−1 − EN
BE depends on• Orbital of the emitted electron• Chemical environment
Valence bands : P2O5 O1s core level of P2O5
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 5/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
Valence band spectraA trivial approach
• Calculation from the density of states of valence electrons• Atomic contributions are weighted by photoionisation cross-sections
VB =∑A,o
σA,o × DOSA,o
γ-Li3PO4 valence band photoionisation cross-sectionAtom Orbital σA,o
Li 2s 0,0008
O2s 0,1405
2p(1/2) 0,00652p(3/2) 0,0128
P3s 0,1116
3p(1/2) 0,01243p(3/2) 0,0244
J.H. Scofield, Journal of Electron Spectroscopyand Related Phenomena, 1976, 8, 129-137
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 6/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
Core level binding energy and chemical shiftsEmpirical point of view and first approach
Core level shifts, initial and final state effects• Core level shifts (CLS) depends on the chemical environment.• CLS splits in a final state and initial state effects.
CLS(ψc) = BEmat, c − BEref, c
CLS(ψci ) =
{Emat, c
N−1 − Eref, cN−1
}−
{Emat
N − ErefN
}final state shift initial state shift
Empirical approachBased on initial state effect :
• Linear behavior of the BE with atomiccharge
• BE decreases when electronic populationincreases
LiCoO2 surface
XPS spectra
L. Dahéron et al., J. Phys. Chem. C, 2009, 113, 5843-5852
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 6/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
Core level binding energy and chemical shiftsEmpirical point of view and first approach
Core level shifts, initial and final state effects• Core level shifts (CLS) depends on the chemical environment.• CLS splits in a final state and initial state effects.
CLS(ψc) = BEmat, c − BEref, c
CLS(ψci ) =
{Emat, c
N−1 − Eref, cN−1
}−
{Emat
N − ErefN
}final state shift initial state shift
Empirical approachBased on initial state effect :
• Linear behavior of the BE with atomiccharge
• BE decreases when electronic populationincreases
LiCoO2 surface
XPS spectra
L. Dahéron et al., J. Phys. Chem. C, 2009, 113, 5843-5852
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM
Roscoff, May 21-27, 2016 – 7/38
OUTL
INE
1 X-Ray Photoemission spectroscopy
2 Computational approach of core level binding energies
3 Application to the study of Li-ion battery materials
4 Conclusion
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 8/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
How to compute core level binding energiesConstraints and key issues
System and formalism we would like• Periodic systems• Density functional theory calculations• Plane waves basis set
Janak theorem
Considering fractional occupation numbers, η, the Janak theorem reads
∂E∂ηi
= ϵi BEc = EN−1 − EN =
∫ 0
1
ϵ(ηi)dηi
Slater-Janak transition state approximation
Assuming εi is a linear function of the occupation number η∫ 0
1
ε(ηi)dηi = −εi(0)−1
2[εi(1)− εi(0)] ≈ −εi(1/2)
J.F. Janak, Phys. Rev. B 1978, 18, 7165.C. Göransson, Phys. Rev. B 2005, 72, 134203.
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 8/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
How to compute core level binding energiesConstraints and key issues
System and formalism we would like• Periodic systems• Density functional theory calculations• Plane waves basis set
Janak theorem
Considering fractional occupation numbers, η, the Janak theorem reads
∂E∂ηi
= ϵi BEc = EN−1 − EN =
∫ 0
1
ϵ(ηi)dηi
Slater-Janak transition state approximation
Assuming εi is a linear function of the occupation number η∫ 0
1
ε(ηi)dηi = −εi(0)−1
2[εi(1)− εi(0)] ≈ −εi(1/2)
J.F. Janak, Phys. Rev. B 1978, 18, 7165.C. Göransson, Phys. Rev. B 2005, 72, 134203.
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 8/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
How to compute core level binding energiesConstraints and key issues
System and formalism we would like• Periodic systems• Density functional theory calculations• Plane waves basis set
Janak theorem
Considering fractional occupation numbers, η, the Janak theorem reads
∂E∂ηi
= ϵi BEc = EN−1 − EN =
∫ 0
1
ϵ(ηi)dηi
Slater-Janak transition state approximation
Assuming εi is a linear function of the occupation number η∫ 0
1
ε(ηi)dηi = −εi(0)−1
2[εi(1)− εi(0)] ≈ −εi(1/2)
J.F. Janak, Phys. Rev. B 1978, 18, 7165.C. Göransson, Phys. Rev. B 2005, 72, 134203.
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 9/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
VASP implementation of core level eigenstates calculationsPAW pseudo-potentials and Z+1 approximation
Computational issues• Core electrons are frozen• Calculations on charged cells are not affordable• Core electrons are not described by atomic orbitals
Z+1 approximation and PAW implementation
all electrons pseudo functionpseudo functionin PAW sphere
all electron inPAW sphere
= - +
|ψ⟩ =∣∣∣ ψ ⟩
+∑
i
(|ϕi⟩ −
∣∣∣ϕi⟩)⟨
pi
∣∣∣ψ⟩• A fraction of electron is extracted from the core and put in the conduction band• The charge nucleus is increased of the same fraction• Assume valence electrons screen the core hole treated as a default• Khon Sham equations are solved in the PAW sphere
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 9/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
VASP implementation of core level eigenstates calculationsPAW pseudo-potentials and Z+1 approximation
Computational issues• Core electrons are frozen• Calculations on charged cells are not affordable• Core electrons are not described by atomic orbitals
Z+1 approximation and PAW implementation
all electrons pseudo functionpseudo functionin PAW sphere
all electron inPAW sphere
= - +
|ψ⟩ =∣∣∣ ψ ⟩
+∑
i
(|ϕi⟩ −
∣∣∣ϕi⟩)⟨
pi
∣∣∣ψ⟩• A fraction of electron is extracted from the core and put in the conduction band• The charge nucleus is increased of the same fraction• Assume valence electrons screen the core hole treated as a default• Khon Sham equations are solved in the PAW sphere
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 10/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
Validity of the computational approachIonic compounds and linearity
Core eigenstates as a functionof occupation number
-220
-200
-180
-160
-140
-120ei
gen
ener
gy /
e
V
P3N
5
P2O
5
Li3PO
4
Li2PO
2N
-570
-555
-540
-525
-510
-495
eigen
ener
gy /
e
V
00.20.40.60.81Occupation number
-435
-420
-405
-390
-375
eigen
ener
gy /
e
Va) P2p
b) O1s
c) N1s
E. Guille, G. Vallverdu et al., J. Chem. Phys.,2014, 141, 244703
System ϵi(1) ϵi(1/2) integralP2O5 O1s -502.33 -536.76 -536.30P3N5 N1s -370.92 -400.87 -400.64γ-Li3PO4 O1s -502.36 -537.35 -535.92Li2PO2N O1s -501.67 -536.06 -534.83
N1s -371.63 -402.20 -401.45
CLScmat = ϵc
mat − ϵcref
• Variation of chemical shifts with respect of P2O5or P3N5 are within 500meV
• γ − Li3PO4 example :
CLSO1s(1/2)− CLSO1s(int) = 0.59− 0.38
= 0.21eV
Main cavits• Janak theorem is limited to the HOMO• Linearity is achieve for deep core state• No spin-orbit coupling for 2p core state
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 10/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
Validity of the computational approachIonic compounds and linearity
Core eigenstates as a functionof occupation number
-220
-200
-180
-160
-140
-120ei
gen
ener
gy /
e
V
P3N
5
P2O
5
Li3PO
4
Li2PO
2N
-570
-555
-540
-525
-510
-495
eigen
ener
gy /
e
V
00.20.40.60.81Occupation number
-435
-420
-405
-390
-375
eigen
ener
gy /
e
Va) P2p
b) O1s
c) N1s
E. Guille, G. Vallverdu et al., J. Chem. Phys.,2014, 141, 244703
System ϵi(1) ϵi(1/2) integralP2O5 O1s -502.33 -536.76 -536.30P3N5 N1s -370.92 -400.87 -400.64γ-Li3PO4 O1s -502.36 -537.35 -535.92Li2PO2N O1s -501.67 -536.06 -534.83
N1s -371.63 -402.20 -401.45
CLScmat = ϵc
mat − ϵcref
• Variation of chemical shifts with respect of P2O5or P3N5 are within 500meV
• γ − Li3PO4 example :
CLSO1s(1/2)− CLSO1s(int) = 0.59− 0.38
= 0.21eV
Main cavits• Janak theorem is limited to the HOMO• Linearity is achieve for deep core state• No spin-orbit coupling for 2p core state
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM
Roscoff, May 21-27, 2016 – 11/38
OUTL
INE
1 X-Ray Photoemission spectroscopy
2 Computational approach of core level binding energies
3 Application to the study of Li-ion battery materials
Core level calculations on LiPON models
Surface reactivity of layered lithium oxides
4 Conclusion
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 12/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
Interface phenomena in Li-ions batteriesSubstantial proportion of interfaces generated during the electrochemical cycles
Li-ions battery
Electrode + Electrode -
Electrolyte
Electron
ElectronElectron
Electron
SEI
Microbattery
Substrate : 1 mm2 to 1 cm2
electrode 1Electrolyte
electrode 2collector collector
10µ
m
Liquid electrolyte cycling• Formation of a Solid Electrolyte
Interphase (SEI)• Result of reductive electrolyte
degradation processes
Solid électrolyte cycling (microbatteries)• solid stacking of electrodes and
electrolyte (LixPOyNz for example)
Conversion materials (higher capacity)• MaXb + (bn)Li −−→ aM + b LinX• Redox processes lead to a composite
electrode (metallic nano sized particlesembedded into a LinX matrix)
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 13/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
Commonly used solid electrolyte in commercial cellsLiPON, a LixPOyNz glass
Assumed structure and migration model of LixPOyNz
Key issues
• What are the recurent patterns in LixPOyNz glasses ?• Nitrogen coordination and role in migration mechanism• Strucutre of LixPOyNz at the interface
R. Marchand et al., J. Non-Crystalline Solids, 1988, 103, 35E. Guille, G. Vallverdu et al., J. Chem. Phys., 2014, 141, 244703
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 14/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
LiPON electrolyte : periodic modelsNitrogen doped systems from lithium phosphate compounds
Dim. LixPOyNz Chain LixPOyNz Li2PO2N
Y.A. Du et al, Phys. Rev. B 2010, 81, 184106
Computed O1s, N1s and P2p Bending energiesO1s (nb) O1s (b) N1s P2p
Dim. LixPOyNz 532.6 395.6 131.6Chain LixPOyNz 532.0 533.2 394.8 130.6
s1-Li2PO2N 533.3 395.7 132.3s2-Li2PO2N 533.3 395.7 132.4s3-Li2PO2N 532.1 394.7 131.3
Exp.(∗) 532.3 533.5 397.9 132.8–133.8(∗)B. Fleutot et al., Solid State Ionics, 2011, 186, 29-36
All experimental dataare not simultaneouslyreproduced.
E. Guille, G. Vallverdu et al., J. Chem. Phys., 2014, 141, 244703
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 14/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
LiPON electrolyte : periodic modelsNitrogen doped systems from lithium phosphate compounds
Dim. LixPOyNz Chain LixPOyNz Li2PO2N
Y.A. Du et al, Phys. Rev. B 2010, 81, 184106
Computed O1s, N1s and P2p Bending energiesO1s (nb) O1s (b) N1s P2p
Dim. LixPOyNz 532.6 395.6 131.6Chain LixPOyNz 532.0 533.2 394.8 130.6
s1-Li2PO2N 533.3 395.7 132.3s2-Li2PO2N 533.3 395.7 132.4s3-Li2PO2N 532.1 394.7 131.3
Exp.(∗) 532.3 533.5 397.9 132.8–133.8(∗)B. Fleutot et al., Solid State Ionics, 2011, 186, 29-36
All experimental dataare not simultaneouslyreproduced.
E. Guille, G. Vallverdu et al., J. Chem. Phys., 2014, 141, 244703
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 15/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
Structural modification of nitrogen dopped structurePossible existence of non-bridging nitrogen
P
O
O
-
-
N
P
O
O
-
-
NP
O
O
-
-
a) Li2PO2N
P
O
O
-
-
O
P
N
O
-
-
NP
O
O
-
-
b) n(Li2PO2N)mod
P
O
O
-
-
N
P
O
O
-
-
NP
O
O
-
-
a) Li2PO2N
P
O
O
-
-
O
P
O
O
-
-
NP
O
O
-
-
b) Li1.5PO2.5N0.5
N1s Bending energies
Conclusion• Presence of non-bridging nitrogen shifts up BE toward experimental value• Available periodic models all fail to reproduce XPS data
Relevant patterns identified from MD amorphisation followed by XPS and Ramancalculations
E. Guille, G. Vallverdu et al., J. Phys. Chem. C, 2015, 119, 23379
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 15/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
Structural modification of nitrogen dopped structurePossible existence of non-bridging nitrogen
P
O
O
-
-
N
P
O
O
-
-
NP
O
O
-
-
a) Li2PO2N
P
O
O
-
-
O
P
N
O
-
-
NP
O
O
-
-
b) n(Li2PO2N)mod
P
O
O
-
-
N
P
O
O
-
-
NP
O
O
-
-
a) Li2PO2N
P
O
O
-
-
O
P
O
O
-
-
NP
O
O
-
-
b) Li1.5PO2.5N0.5
N1s Bending energies
Conclusion• Presence of non-bridging nitrogen shifts up BE toward experimental value• Available periodic models all fail to reproduce XPS data
Relevant patterns identified from MD amorphisation followed by XPS and Ramancalculations
E. Guille, G. Vallverdu et al., J. Phys. Chem. C, 2015, 119, 23379
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 15/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
Structural modification of nitrogen dopped structurePossible existence of non-bridging nitrogen
P
O
O
-
-
N
P
O
O
-
-
NP
O
O
-
-
a) Li2PO2N
P
O
O
-
-
O
P
N
O
-
-
NP
O
O
-
-
b) n(Li2PO2N)mod
P
O
O
-
-
N
P
O
O
-
-
NP
O
O
-
-
a) Li2PO2N
P
O
O
-
-
O
P
O
O
-
-
NP
O
O
-
-
b) Li1.5PO2.5N0.5
N1s Bending energies
Conclusion• Presence of non-bridging nitrogen shifts up BE toward experimental value• Available periodic models all fail to reproduce XPS data
Relevant patterns identified from MD amorphisation followed by XPS and Ramancalculations
E. Guille, G. Vallverdu et al., J. Phys. Chem. C, 2015, 119, 23379
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM
Roscoff, May 21-27, 2016 – 16/38
OUTL
INE
1 X-Ray Photoemission spectroscopy
2 Computational approach of core level binding energies
3 Application to the study of Li-ion battery materials
Core level calculations on LiPON models
Surface reactivity of layered lithium oxides
4 Conclusion
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 17/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
Surface reactivity of layered lithium oxidesA coupled experimetal-theoretical study
Synthesis and elaboration : Manage surface and morphology
Experimental sample
Computational approach• model compounds• relevant surface model
Surface reactivity : Indirect approach from gaz probes adsorption
XPS characterisation
Identification of active sites(type/number)
DFT periodic calculations
• Electronic processes• Electronic density analyses
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 18/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
SO2 adsorption on (101) and (001) surfaces of Li2MnO3XPS scale of S2p chemical shifts
Slater-Janak transition state approximation
Assuming εi is a linear function of the occupation number η
EN−1 − EN =
∫ 0
1
ε(ηi)dηi = −εi(0)−1
2[εi(1)− εi(0)] ≈ −εi(1/2)
Li2MnO3 surfaces used to investigatereactivity aginst SO2
• (110) and (001) surfaces• Sulfate (bridge) and sulfite (top) sites
CLS of S2p
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 19/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
SO2 adsorption on (101) and (001) surfaces of Li2MnO3Comparison with experimental results
Comp.Exp. 169 eV 167 eV 162 eV
M
SO2
Dissociative
Redox
OS O
OSulfite AX3E1
Ac/Base
O OS
O OSulfate
RedoxOS
O OSulfite AX3
Redox
sulfate (110)qS=3.60
sulfite (001)qS=3.35
sulfate (001)qS=3.40
sulfite (110)qS=2.16
• Identification of adsorbed species• Electronic processes taking place• Lack of spin orbit coupling for S2p core level
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 19/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
SO2 adsorption on (101) and (001) surfaces of Li2MnO3Comparison with experimental results
Comp.Exp. 169 eV 167 eV
167.1 eV
162 eV
168.8 eV 168 eV
M
SO2
Dissociative
Redox
OS O
OSulfite AX3E1
Ac/Base
O OS
O OSulfate
RedoxOS
O OSulfite AX3
Redox
?
sulfate (110)qS=3.60
sulfite (001)qS=3.35
sulfate (001)qS=3.40
sulfite (110)qS=2.16
• Identification of adsorbed species• Electronic processes taking place• Lack of spin orbit coupling for S2p core level
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 19/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
SO2 adsorption on (101) and (001) surfaces of Li2MnO3Comparison with experimental results
Comp.Exp. 169 eV 167 eV
167.1 eV
162 eV
168.8 eV 168 eV
M
SO2
Dissociative
Redox
OS O
OSulfite AX3E1
Ac/Base
O OS
O OSulfate
RedoxOS
O OSulfite AX3
Redox
?
sulfate (110)qS=3.60
sulfite (001)qS=3.35
sulfate (001)qS=3.40
sulfite (110)qS=2.16
• Identification of adsorbed species• Electronic processes taking place• Lack of spin orbit coupling for S2p core level
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM
Roscoff, May 21-27, 2016 – 20/38
OUTL
INE
1 X-Ray Photoemission spectroscopy
2 Computational approach of core level binding energies
3 Application to the study of Li-ion battery materials
4 Conclusion
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 21/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
Conclusion and perspectivesMainly perspectives ...
VASP implementation of the Janak theorem
• The Slater-Janak transition state approximation may be relevant for insulators
• We applied the method to• better understand CLS and corel level structure• the identification of reccuring patterns in an amorphous solid electrolyte• the investigation of surface reactivity of layered lithium oxides• the identification of oxydation degrees of transition metals
Theoretical challenges about core level bending energy calculations
• Core electrons relaxations with reasonnable computational cost• Core excited state of cations in periodic calculations : multideterminental approach ?• Spin-orbit coupling for p and d core states• Cross sections of ionization processes
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 21/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
Conclusion and perspectivesMainly perspectives ...
VASP implementation of the Janak theorem
• The Slater-Janak transition state approximation may be relevant for insulators
• We applied the method to• better understand CLS and corel level structure• the identification of reccuring patterns in an amorphous solid electrolyte• the investigation of surface reactivity of layered lithium oxides• the identification of oxydation degrees of transition metals
Theoretical challenges about core level bending energy calculations
• Core electrons relaxations with reasonnable computational cost• Core excited state of cations in periodic calculations : multideterminental approach ?• Spin-orbit coupling for p and d core states• Cross sections of ionization processes
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 22/22
Émilie Guille Isabelle Baraille Didier Bégué Yann Tison
A. Quesne-Turin Delphine Flahaut L. Croguennec Michel Ménétrier
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 22/22
Émilie Guille Isabelle Baraille Didier Bégué Yann Tison
A. Quesne-Turin Delphine Flahaut L. Croguennec Michel Ménétrier
Thank you for your attention
CONTACT
Germain Vallverdu
UPPA / IPREM
http://gvallver.perso.univ-pau.fr
@gvallverdu
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 23/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
LixPOyNz agregates obtained from molecular dynamics simulationsRecurent pattern and chain lengths
Amorphisation of � –Li3PO4 : LiPON in silicoComputational details
• DL_POLY• Born-Mayer pair potential• NPT simulations (1-2 ns)• box 32×32×26 Å (2400 atoms)
Simulation box before and after amorphisation
Conclusion• PO4
3– tetrahedron form short chains of 2 to 3 units.• Agree with HPLC measurements (Wang et al J. Non-Crystalline Solids, 1995, 183, 297)
E. Guille, G. Vallverdu et al., J. Phys. Chem. C, 2015, 119, 23379
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 22/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
LixPOyNz agregates obtained from molecular dynamics simulationsRecurent pattern and chain lengths
Amorphisation of � –Li3PO4 : LiPON in silicoComputational details
• DL_POLY• Born-Mayer pair potential• NPT simulations (1-2 ns)• box 32×32×26 Å (2400 atoms)
Simulation box before and after amorphisation
Conclusion• PO4
3– tetrahedron form short chains of 2 to 3 units.• Agree with HPLC measurements (Wang et al J. Non-Crystalline Solids, 1995, 183, 297)
E. Guille, G. Vallverdu et al., J. Phys. Chem. C, 2015, 119, 23379
XPS chemical shiftsGermain Vallverdu, UPPA / IPREM Roscoff, May 21-27, 2016 – 22/22
XPS spectra
Computationalapproach
Li-ionLiPON ElectrolyteSurface reactivity
Conclusion
Vibrational characteristics of LiPON agregatesSimulation of Raman spectra
Raman experimental spectra Simulated Raman spectra
600 700 800 900 1000 1100 1200
wavenumber (cm-1
)
0
0.5
1
1.5
Rel
ativ
e in
ten
sity
LiPON-40 (exp)
C0, C2, C4
C0, C2, C3
C0, C1, C2
695 cm-1
800 cm-1
950 cm-1
1025 cm-1
case 3
case 2
case 1
• Raman spectra are correctly reproduced by superimposing individual spectra of agregates• 695 - 800−1 region is described by a combination mode involving non-bridging nitrogen
atomsRelevant patterns
C0 C3 C4