The energy separation of the higher lying cation XPS binding energies, BEs, for MgO is examined. It is shown that the Hartree–Fock BEs overestimate the separation of the Mg BE(2s) and BE(2p), because an important many-body effect is neglected in the determination of the Hartree–Fock BEs. Once the many-body effect is taken into account, there is good agreement between theory and the XPS measurement. The character of this atomic many-body effect is established in terms of a nearly degenerate configuration that is needed to describe the wavefunction when an Mg 2s electron is ionized. The results provide additional evidence of the ionic character of the MgO crystal. Given the atomic character of the many-body effect, it is likely to apply also to the BE separations of other closed shell oxides.

1.
P. S.
Bagus
,
E.
Ilton
, and
C. J.
Nelin
,
Catal. Lett.
148
,
1785
(
2018
).
2.
C. S.
Fadley
,
D. A.
Shirley
,
A. J.
Freeman
,
P. S.
Bagus
, and
J. V.
Mallow
,
Phys. Rev. Lett.
23
,
1397
(
1969
).
3.
P. S.
Bagus
,
A. J.
Freeman
, and
F.
Sasaki
,
Phys. Rev. Lett.
30
,
850
(
1973
).
4.
P. S.
Bagus
,
E. S.
Ilton
, and
C. J.
Nelin
,
Surf. Sci. Rep.
68
,
273
(
2013
).
5.
E.-K.
Viinikka
and
Y.
Öhrn
,
Phys. Rev. B
11
,
4168
(
1975
).
6.
P. S.
Bagus
,
R.
Broer
, and
F.
Parmigiani
,
Chem. Phys. Lett.
421
,
148
(
2006
).
7.
R. S.
Mulliken
,
J. Chim. Phys.
46
,
497
(
1949
).
8.
9.
S. E.
Derenzo
,
M. K.
Klintenberg
, and
M. J.
Weber
,
J. Chem. Phys.
112
,
2074
(
2000
).
10.
P. S.
Bagus
,
M. J.
Sassi
, and
K. M.
Rosso
,
J. Chem. Phys.
151
,
044107
(
2019
).
11.
C. J.
Nelin
,
F.
Uhl
,
V.
Staemmler
,
P. S.
Bagus
,
Y.
Fujimori
,
M.
Sterrer
,
H.
Kuhlenbeck
, and
H.-J.
Freund
,
Phys. Chem. Chem. Phys.
16
,
21953
(
2014
).
12.
C. E.
Moore
,
Atomic Energy Levels, National Bureau of Standards No. 467
(
U.S. GPO
,
Washington, DC
,
1952
), see also http://physics.nist.gov/cgi-bin/AtData/main_asd.
13.
J. Q.
Broughton
and
P. S.
Bagus
,
Phys. Rev. B
36
,
2813
(
1987
).
14.
15.
E.
Valderrama
,
E. V.
Ludena
, and
J.
Hinze
,
J. Chem. Phys.
110
,
2343
(
1999
).
16.
C. F.
Fischer
,
Comput. Phys. Commun.
128
,
635
(
2000
).
17.
I. N.
Levine
,
Quantum Chemistry
(
Prentice-Hall
,
Upper Saddle River
,
NJ
,
2000
).
18.
T.
Saue
 et al,
J. Chem. Phys.
152
,
204104
(
2020
).
19.
clips is a program system to compute ab initio SCF and correlated wavefunctions for polyatomic systems. It has been developed based on the publicly available programs in the ALCHEMY package from the IBM San Jose Research Laboratory by P. S. Bagus, B. Liu, A. D. McLean, and M. Yoshimine.
20.
B. O.
Roos
,
P. R.
Taylor
, and
P. E. M.
Siegbahn
,
Chem. Phys.
48
,
157
(
1980
).
21.
dirac, a relativistic ab initio electronic structure program, Release DIRAC14 (2014), written by T. Saue, L. Visscher, H. J. Aa. Jensen, and R. Bast, with contributions from V. Bakken, K. G. Dyall, S. Dubillard, U. Ekström, E. Eliav, T. Enevoldsen, E. Faßhauer, T. Fleig, O. Fossgaard, A. S. P. Gomes, T. Helgaker, J. Henriksson, M. Iliaš, Ch. R. Jacob, S. Knecht, S. Komorovský, O. Kullie, C. V. Larsen, J. K. Lærdahl, Y. S. Lee, H. S. Nataraj, P. Norman, G. Olejniczak, J. Olsen, Y. C. Park, J. K. Pedersen, M. Pernpointner, R. di Remigio, K. Ruud, P. Sałek, B. Schimmelpfennig, J. Sikkema, A. J. Thorvaldsen, J. Thyssen, J. van Stralen, S. Villaume, O. Visser, T. Winther, and S. Yamamoto, see http://www.diracprogram.org.
22.
P. S.
Bagus
,
C. R.
Brundle
, and
B. V.
Crist
,
J. Vac. Sci. Technol. A
39
,
063206
(
2021
).
24.
L.
Visscher
,
O.
Visser
,
P. J. C.
Aerts
,
H.
Merenga
, and
W. C.
Nieuwpoort
,
Comput. Phys. Commun.
81
,
120
(
1994
).
25.
J. C.
Slater
,
Quantum Theory of Atomic Structure
(
McGraw-Hill
,
New York
,
1960
), Vols. I and II.
26.
L. D.
Landau
and
E. M.
Lifshitz
,
Quantum Mechanics
(
Addison-Wesley
,
Reading
,
1958
).
27.
R. W. G.
Wyckoff
,
Crystal Structures
(
Wiley
,
New York
,
1963
).
28.
See supplementary material at https://www.scitation.org/doi/suppl/10.1116/6.0001655 for information describing computational details.

Supplementary Material

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