Second-Order Perturbative Analysis
of Donor-Acceptor Interactions (E2PERT)
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Reference
A. E. Reed, L. A. Curtiss, and F. Weinhold, Chem. Rev. 88, 899-926 (1988);
F. Weinhold, "Natural Bond Orbital Methods," in P. v. R. Schleyer (ed.), Encyclopedia of Computational Chemistry, Vol. 3, pp. 1792-1811 (1998)
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Notes
2nd-order energetic analysis is performed by default ("E2PERT" keyword is optional). All possible NBO donor-acceptor pairs are checked and 2nd-order stabilization energies are printed for interactions above a user-selectable threshold (default: 0.5 kcal/mol for intramolecular, 0.1 kcal/mol for intermolecular interactions). Results are illustrated for the formamide molecule, RHF/3-21G level at B3LYP/6-311++G** geometry (see NBO 6.0 Manual, p. A21 for additional discussion).
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Sample Input (G9X)
#rhf/3-21g pop=nbo
RHF/3-21G for formamide (H2NCHO)
0 1
H -1.908544 0.420906 0.000111
H -1.188060 -1.161135 0.000063
N -1.084526 -0.157315 0.000032
C 0.163001 0.386691 -0.000154
O 1.196265 -0.246372 0.000051
H 0.140159 1.492269 0.000126