 


Example 2: P3+ / 6311+G(2df) calculations of vertical electron affinities (VEAs)
of sodium chloride molecule
Input to G16 program:
#p ept(p3,ReadOrbitals) 6311+G(2df)
Title: P3+ calculations for VEAs of sodium chloride.
0 1
Na
Cl 1 2.360
5 6
This input is similar to the one of Example 1.
Calculations are carried out for sodium chloride molecule, which has 28 electrons in 14 molecular orbitals.
10 out of these 14 occupied orbitals will be frozen by default and the remaining occupied orbitals used for correlation
will be numbered from 1 through 4, and the LUMO orbital will have no. 5. The above input therefore requests (through the last line 5 6)
vertical electron attachment energy (VEAE) calculations to LUMO and LUMO+1 orbitals.
The resulting output gives these VEAEs as:
Summary of results for alpha spinorbital 5 P3:
Koopmans theorem: 0.19916D01 au 0.542 eV
Converged second order pole: 0.22971D01 au 0.625 eV 0.995 (PS)
Converged 3rd order P3 pole: 0.23094D01 au 0.628 eV 0.994 (PS)
Renormalized (P3+) P3 pole: 0.23085D01 au 0.628 eV 0.995 (PS)
Summary of results for alpha spinorbital 6 P3:
Koopmans theorem: 0.12671D01 au 0.345 eV
Converged second order pole: 0.12076D01 au 0.329 eV 0.999 (PS)
Converged 3rd order P3 pole: 0.12035D01 au 0.327 eV 0.999 (PS)
Renormalized (P3+) P3 pole: 0.12038D01 au 0.328 eV 0.999 (PS)
Similarly as in Example 1,
results are reported not only for P3+, but for Koopmans's theorem, D2 and P3, as well.
Pole strengths (PS) reported in the last column are equal to the norms of a Dyson orbitals corresponding to VEAEs
and are calculated from residues at VEAEs.
We recall that:
PS values below 0.85 indicate that the diagonal selfenergy
approximations (i.e., D2, D3, OVGF, P3, P3+)
are unreliable!!!
Sign convention:
Numbers reported above are VEAEs
defined as the total energy of the (N+1)electron system minus the
total energy of the Nelectron system. A negative value of VEAEs
therefore means that the (N+1)electron system is bound. VEA is a negative of
VEAE and hence above results for orbital no. 5 (LUMO) correspond to an exoenergetic process of
electron attachment and show that sodium chloride anion is more stable than the neutral species.
In contrast, electron attachment to orbital no. 6 (LUMO+1) of sodium chloride is an exoenergetic process.
Note an
important
change in the basis set compared to Example 1:
now the "+" sign has been added to the basis set name, which denotes that the basis set has
been augmented with diffuse functions, necessary to span the space in the outer regions of the molecule
where the electron attachment process takes place. Note that only one "+" is added, since there are no
hydrogen atoms in the molecule; for the same reason, the "2pd" part has been dropped in the parenthesis
compared to Example 1.
Instead of the 6311+G(2df) basis, we could have used another
triplezeta quality basis containing both polarization and diffuse functions, e.g., the
correlationconsistent augccpVTZ basis.
 