# Example: Core-electron binding energies (CEBE): NNO¶

Download CEBE_NNO.run

#!/bin/sh

# ADF is well suited for calculating Core Electron Binding Energies (CEBEs). In
# this example it is shown how one can differentiate between the 1s CEBEs of the
# two non-equivalent nitrogen atoms in N2 O, using a delta-SCF technique. It
# starts with a regular calculation that has the purpose of preparing a
# reference adf.rkf file for the NNO molecule, which will later be useful in the
# energy analysis. The result file is saved to t21.NNO.

# The same GGA functional is specified throughout the run. The amount of output
# is reduced by using some print keys.

# The prepare the nitrogen atom with a core hole (restricted) will be used as a
# fragment later. This enables selection of where the core hole should be.

# prepare the Nitrogen core hole restricted to be used as fragment

AMS_JOBNAME=N_ch $AMSBIN/ams <<eor System atoms N 0.0 0.0 0.0 end end Task SinglePoint Engine ADF title N atom core hole irrepoccupations s 1 2 p 3 end basis type TZ2P core None CreateOutput Yes end numericalquality good xc gga pw86x pw91c end EndEngine eor # Now perform the restricted ground state molecule for analysis later. The # adf.rkf result file is saved. # Remark: In the core hole calculation the 2 N atoms will have different fragments. # Therefore also in this calculation the 2 N atoms are treated with 2 different fragments, # which is done here by using 2 different region: 'one' and 'two' AMS_JOBNAME=NNO$AMSBIN/ams <<eor
System
atoms
N   0.0    0.0    -1.1284  region=one
N   0.0    0.0     0.0     region=two
O   0.0    0.0     1.1841
end
end

title NNO
basis
type TZ2P
core None
end
noprint sfofragpop fragsfo
numericalquality good
xc
gga pw86x pw91c
end
EndEngine

eor

# Next follow two sets of almost identical calculations in which a 1s electron
# is removed from one or the other N atom (please note that the deepest s level
# is associated with the 1s of the oxygen atom). The molecular NNO result file
# is used as fragment. An unrestricted calculation is done and a positive charge
# is specified. The final result file for the molecule with the core hole is
# saved. Then another calculation is done to conveniently obtain the energy with
# respect to the normal molecule. This is repeated for a core hole on the other
# N atom.

AMS_JOBNAME=NNO_unr1 $AMSBIN/ams <<eor System atoms N 0.0 0.0 -1.1284 region=one adf.f=N_ch N 0.0 0.0 0.0 region=two O 0.0 0.0 1.1841 end charge 1 end Task SinglePoint Engine ADF title NNO unrestricted core hole fragments N_ch N_ch.results/adf.rkf end irrepoccupations sigma 1 1 1 4 // 1 0 1 4 pi 4 // 4 end basis type TZ2P core None end noprint sfofragpop fragsfo numericalquality good spinpolarization 1 unrestricted Yes xc gga pw86x pw91c end EndEngine eor # In the second calculation the result file of one of the unrestricted NNO # calculations is used as restart file, which ensures that the hole stays at its # place, because the starting density is already correct. The result file # t21.NNO for the normal NNO calculation is specified as fragment to serve as an # energy reference. The final Bonding Energy printed by ADF indicates what the # CEBE is. However, please check Chong, D.P. Accurate DFT Calculation of Core- # Electron Binding Energies in Reviews in Modern Quantum Chemistry, A # Celebration of the Contributions of R.G. Parr, edited by K.D. Sen (World # Scientific Publishing Co., Singapore), 1106-1139 (2002) for more detailed # information on Core-Electron Binding Energies. This reference also contain # information on empirical corrections that may have to be made on the final # numbers. AMS_JOBNAME=NNO_unr1_1$AMSBIN/ams <<eor
System
atoms
N   0.0    0.0    -1.1284  region=one  adf.f=NNO
N   0.0    0.0     0.0     region=two  adf.f=NNO
end
charge 1
end

title NNO unr. core hole
fragments
end
irrepoccupations
sigma  1 1 1 4 // 1 0 1 4
pi     4       // 4
end
noprint sfofragpop fragsfo
numericalquality good
spinpolarization 1
unrestricted Yes
xc
gga pw86x pw91c
end
EndEngine

eor

# core hole nr. 2

AMS_JOBNAME=NNO_unr2 $AMSBIN/ams <<eor System atoms N 0.0 0.0 -1.1284 region=one N 0.0 0.0 0.0 region=two adf.f=N_ch O 0.0 0.0 1.1841 end charge 1 end Task SinglePoint Engine ADF title NNO unrestricted core hole fragments N_ch N_ch.results/adf.rkf end irrepoccupations sigma 1 1 1 4 // 1 0 1 4 pi 4 // 4 end basis type TZ2P core None end noprint sfofragpop fragsfo numericalquality good spinpolarization 1 unrestricted Yes xc gga pw86x pw91c end EndEngine eor # analysis for core hole 2 AMS_JOBNAME=unr3$AMSBIN/ams <<eor
System
atoms
N   0.0    0.0    -1.1284  region=one  adf.f=NNO
N   0.0    0.0     0.0     region=two  adf.f=NNO
end
charge 1
end

title NNO unr. core hole
fragments
end
irrepoccupations
sigma  1 1 1 4 // 1 0 1 4
pi     4       // 4
end
noprint sfofragpop fragsfo
numericalquality good
spinpolarization 1
unrestricted Yes
xc
gga pw86x pw91c
end
EndEngine

eor

# Similarly, one could easily have prepared an oxygen with a core hole and
# determined the CEBE of the oxygen 1s atom.