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Table 3 Stacking energies (in kcal mol−1) for several orientations of the cytosine dimer (see Scheme 3), computed with various density functionals and MP2a,b

From: π-π stacking tackled with density functional theory

orientation MP2b,c MP2ccb,d LDA KT1 KT2 BHandH PW91 BLYP BP86 OLYP B3LYP X3LYP
1 2.2 2.5 2.7 2.3 2.7 3.9 8.0 11.7 10.9 16.5 10.9 9.9
2 −3.1 −3.8 −3.7 −3.9 −3.5 −3.3 2.6 6.5 5.4 12.3 5.2 4.1
3 −7.2 −8.9 −8.8 −8.7 −8.3 −9.0 −2.1 1.7 0.7 8.0 0.2 −1.0
4 −8.3 −9.9 −9.4 −9.2 −8.9 −10.1 −2.9 0.8 −0.1 6.9 −0.9 −2.1
5 0.2 0.3 0.6 0.1 0.6 1.5 6.4 10.3 9.3 15.7 9.3 8.3
6 0.5 0.6 0.8 0.4 0.8 1.8 6.8 10.8 9.7 16.3 9.8 8.8
7 −0.5 −1.0 −0.7 −0.9 −0.6 0.2 2.8 5.5 5.2 8.7 5.0 4.2
8 −7.3 −9.1 −8.4 −8.3 −7.9 −8.8 −3.0 0.2 −0.2 5.6 −1.2 −2.2
9 −7.6 −9.1 −8.7 −8.5 −8.2 −9.4 −2.3 1.5 0.5 7.3 −0.2 −1.4
10 −6.6 −8.3 −7.9 −7.7 −7.5 −8.3 −1.8 1.8 0.9 7.6 0.3 −0.8
11 −7.6 −9.4 −8.8 −8.5 −8.3 −9.5 −2.8 0.6 −0.1 6.2 −1.0 −2.1
12 −5.5 −7.4 −6.7 −6.6 −6.2 −7.0 −3.6 −1.6 −1.4 1.5 −2.4 −3.1
13 −7.4 −8.8 −8.3 −8.1 −7.9 −8.6 −3.0 0.4 −0.4 5.2 −1.0 −2.0
14 −7.0 −9.1 −8.8 −8.7 −8.4 −9.4 −2.1 1.6 0.7 8.0 −0.1 −1.3
  MAD1 e   0.94 0.81 0.60 1.49 4.87 8.35 7.58 13.63 7.06 6.03
  MAD2 f   0.38 0.47 0.72 0.52 6.04 9.52 8.75 14.80 8.24 7.21
  1. aPost-SCF on LDA/TZ2P orbitals and densities, see Computational details
  2. bFrom [21]
  3. cMP2/6-31G*(0.25) results
  4. dMP2 with complete-basis-set (CBS) extrapolation, i.e. MP2/CBS, corrected for Δ[CCSD(T)/6-31G*(0.25) - MP2/6-31G*(0.25)]
  5. eMean Absolute Deviation (in kcal mol−1) of DFT energies from MP2/6-31G*(0.25) data
  6. fMean Absolute Deviation (in kcal mol−1) of DFT energies from MP2/CBS corrected for Δ[CCSD(T)/6-31G*(0.25) - MP2/6-31G*(0.25)]