TY - JOUR
T1 - The Effects of Higher Orders of Perturbation Theory on the Correlation Energy of Atoms and Bonds in Molecules
AU - Vincent, Mark
AU - Silva, Arnaldo F
AU - Mcdonagh, James
AU - Popelier, Paul
PY - 2017
Y1 - 2017
N2 - 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 (IQA). 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 H2 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 towards the MP2 values. Furthermore, each individual part of a molecule or complex (atom or bond) has a specific convergence pattern for the MPn series: through-space interactions converge at MP2 but bonds converge at MP3 level. The atomic correlation energy appears to head towards convergence at the MP4 level.
AB - 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 (IQA). 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 H2 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 towards the MP2 values. Furthermore, each individual part of a molecule or complex (atom or bond) has a specific convergence pattern for the MPn series: through-space interactions converge at MP2 but bonds converge at MP3 level. The atomic correlation energy appears to head towards convergence at the MP4 level.
U2 - 10.1002/qua.25519
DO - 10.1002/qua.25519
M3 - Article
SN - 0020-7608
JO - International Journal of Quantum Chemistry
JF - International Journal of Quantum Chemistry
ER -