Approach (using biphenyl):
1. Draw biphenyl -- the dihedral angle between the two rings should be about 38 degrees
2. Optimize structure using b3lyp/6-31+g in gas phase. Gives you E1
3. Change the charge and multiplicity to +1 and 2, respectively.
4. Calculate single-point energy using the previously optimised structure (from step 2, i.e. don't optimise). Gives E2.
5. Now, optimise structure. Gives E3.
6. Change the charge and multiplicity to 0 and 1. Calculate single point energy of the optimised structure in step 5. Gives E4.
7. ΔE=(E2-E3)+(E4-E1). Convert energies from Hartree to eV by multiplying by 27.2107
Using nwchem:
title "Calculating E1"and
start neutral_ground_state
geometry
C 3.58691 -1.70661e-06 0.000280946
C 2.87790 -0.739281 0.946515
C 1.48493 -0.738173 0.945097
C 0.747197 0.00000 0.000278762
C 1.48488 0.738183 -0.944553
C 2.87785 0.739273 -0.945948
C -0.747197 0.00000 0.000278762
C -1.48488 0.00000 -1.19873
C -2.87785 0.00000 -1.20050
C -1.48493 0.00000 1.19927
C -3.58691 0.00000 0.000281534
C -2.87790 0.00000 1.20107
H 4.67272 9.42775e-05 0.000158092
H 3.40921 -1.32260 1.69312
H 0.975305 -1.32691 1.69865
H 3.40931 1.32254 -1.69249
H -3.40931 0.00000 -2.14788
H -0.975305 0.00000 2.15554
H -4.67272 0.00000 0.000125630
H -3.40921 0.00000 2.14853
H -0.975288 0.00000 -2.15502
H 0.975288 1.32693 -1.69812
end
charge 0
basis "ao basis" cartesian print
H library "6-31G**"
C library "6-31G**"
end
dft
direct
grid fine
xc b3lyp
mult 1
end
task dft optimize
title "Calculating E2"
start cation_excited_state
geometry units angstrom
C 0.00000 -3.56301 0.00000
C -1.13927 -2.85928 -0.393841
C -1.13879 -1.46545 -0.394153
C 0.00000 -0.742814 0.00000
C 1.13879 -1.46545 0.394153
C 1.13927 -2.85928 0.393841
C 0.00000 0.742814 0.00000
C 1.13879 1.46545 -0.394153
C 1.13927 2.85928 -0.393841
C -1.13879 1.46545 0.394153
C 0.00000 3.56301 0.00000
C -1.13927 2.85928 0.393841
H 0.00000 -4.64896 0.00000
H -2.02827 -3.39662 -0.711607
H -2.02148 -0.928265 -0.727933
H 2.02827 -3.39662 0.711607
H 2.02827 3.39662 -0.711607
H -2.02148 0.928265 0.727933
H 0.00000 4.64896 0.00000
H -2.02827 3.39662 0.711607
H 2.02148 0.928265 -0.727933
H 2.02148 -0.928265 0.727933
end
charge 1
basis "ao basis" cartesian print
H library "6-31G**"
C library "6-31G**"
end
dft
direct
grid fine
xc b3lyp
mult 2
end
task dft energy
and
title "Calculating E3"
start cation_ground_state
geometry units angstrom
C 0.00000 -3.56301 0.00000
C -1.13927 -2.85928 -0.393841
C -1.13879 -1.46545 -0.394153
C 0.00000 -0.742814 0.00000
C 1.13879 -1.46545 0.394153
C 1.13927 -2.85928 0.393841
C 0.00000 0.742814 0.00000
C 1.13879 1.46545 -0.394153
C 1.13927 2.85928 -0.393841
C -1.13879 1.46545 0.394153
C 0.00000 3.56301 0.00000
C -1.13927 2.85928 0.393841
H 0.00000 -4.64896 0.00000
H -2.02827 -3.39662 -0.711607
H -2.02148 -0.928265 -0.727933
H 2.02827 -3.39662 0.711607
H 2.02827 3.39662 -0.711607
H -2.02148 0.928265 0.727933
H 0.00000 4.64896 0.00000
H -2.02827 3.39662 0.711607
H 2.02148 0.928265 -0.727933
H 2.02148 -0.928265 0.727933
end
charge 1
basis "ao basis" cartesian print
H library "6-31G**"
C library "6-31G**"
end
dft
direct
grid fine
xc b3lyp
mult 2
end
task dft optimize
title "Calculating E4"
start neutral_excited_state
geometry
C 0.00000 -3.54034 0.00000
C -1.20296 -2.84049 -0.216000
C -1.20944 -1.46171 -0.206253
C 0.00000 -0.721866 0.00000
C 1.20944 -1.46171 0.206253
C 1.20296 -2.84049 0.216000
C 0.00000 0.721866 0.00000
C 1.20944 1.46171 -0.206253
C 1.20296 2.84049 -0.216000
C -1.20944 1.46171 0.206253
C 0.00000 3.54034 0.00000
C -1.20296 2.84049 0.216000
H 0.00000 -4.62590 0.00000
H -2.12200 -3.38761 -0.395378
H -2.13673 -0.938003 -0.401924
H 2.12200 -3.38761 0.395378
H 2.12200 3.38761 -0.395378
H -2.13673 0.938003 0.401924
H 0.00000 4.62590 0.00000
H -2.12200 3.38761 0.395378
H 2.13673 0.938003 -0.401924
H 2.13673 -0.938003 0.401924
end
charge 0
basis "ao basis" cartesian print
H library "6-31G**"
C library "6-31G**"
end
dft
direct
grid fine
xc b3lyp
mult 1
end
task dft energy
And it all gives:
E1: Total DFT energy = -463.321927500065ΔE=-463.035336642074-(-463.042292962541)+(-463.315725187090-(-463.321927500065))=0.013158633442Hartree= .3580556270002294 eV ≅ 0.36 eV i.e. the same as the paper.
E2: Total DFT energy = -463.035336642074
E3: Total DFT energy = -463.042292962541
E:4 Total DFT energy = -463.315725187090