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The effects of higher orders of perturbation theory on the correlation energy of atoms and bonds in molecules
Author(s) -
Vincent Mark A.,
Silva Arnaldo F.,
McDonagh James L.,
Popelier Paul L. A.
Publication year - 2018
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.25519
Subject(s) - bond energy , chemistry , electronic correlation , atom (system on chip) , perturbation theory (quantum mechanics) , correlation , molecule , perturbation (astronomy) , bond length , range (aeronautics) , atomic physics , atoms in molecules , energy (signal processing) , space (punctuation) , physics , quantum mechanics , materials science , mathematics , linguistics , philosophy , geometry , computer science , composite material , embedded system
We examine, for the first time, the effects of higher orders of Møller–Plesset perturbation theory on the individual atoms within a molecule and the bonds between them, via the topological energy partitioning method of interacting quantum atoms. In real terms (i.e., not by absolute value) MP3 decreases the correlation energy of a bond, and MP4SDQ also decreases the energy of the atoms at either end of the bond. In addition, we investigated long‐range through‐space dispersive effects on a H 2 oligomer. Overall, MP3 is the largest correction to the correlation energy, and most of that energy is allocated to chemical bonds, reducing their values in actual terms. The MP4SDQ bond correlation correction, despite being relatively small, tends to have two effects: (i) for small or negative correlation energies MP4SDQ tends to decrease the bond correlation values even more, and (ii) for large (positive) bond correlation energies MP4SDQ tends to restore the bond correlation energies from the MP3 back toward the MP2 values. Furthermore, each individual part of a molecule or complex (atom or bond) has a specific convergence pattern for the MP n series: through‐space interactions converge at MP2 but bonds converge at MP3 level. The atomic correlation energy appears to head toward convergence at the MP4 level.