Electron density and its reduced density gradient in the study of π–π interactions.
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| Title: | Electron density and its reduced density gradient in the study of π–π interactions. |
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| Authors: | Morales‐Pumarino, Daniela1 (AUTHOR), Barquera‐Lozada, José E.1 (AUTHOR) jebarque@unam.mx |
| Source: | International Journal of Quantum Chemistry. Sep2023, Vol. 123 Issue 18, p1-10. 10p. |
| Subjects: | Electron density, Dispersive interactions, Kinetic energy, Biomaterials, Density functional theory |
| Abstract: | π−π interactions are unique dispersive interactions that are important for biological systems and materials, but the study of this interaction is not trivial. It is well‐known that density functional theory (DFT) does not describe these interactions correctly and only with empirical dispersion corrections, it produces accurate energies. Moreover, little is known about the error in the electron density (ρr). Non‐Covalent Interaction method (NCI) has been used to analyze π stacking from the electron density. However, for these interactions, the information that can be extracted with this method is quite limited. We compare the DFT and CCSD intermolecular ρr. The correlation between both densities is close to one, but DFT underestimates its value. To evaluate, if the strength of the π−π interaction can be qualitatively inferred from density related scalar fields, we study the correlation between these fields (ρr multiplied by the sign of the second eigenvalue of its hessian, signλ2ρ, the laplacian of ρr, ∇2ρr, the virial field, Vr, the Lagrangian, Gr, and the Hamiltonian, Kr, kinetic energy density) and the interaction energy. Surprisingly, all the scalar fields have a better correlation with the energy than signλ2ρ. This quantity is normally plotted over the reduced density gradient (RDG) isosurface in the NCI method to get an insight of intermolecular interactions, but the other scalar fields give a better picture of the energetic nature of π−π interactions. Moreover, we show that signλ2ρ cannot be used as an indicator of repulsive interactions (positive values), because for the studied π systems, the more energetic the interaction is, the more positive signλ2ρ. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | π−π interactions are unique dispersive interactions that are important for biological systems and materials, but the study of this interaction is not trivial. It is well‐known that density functional theory (DFT) does not describe these interactions correctly and only with empirical dispersion corrections, it produces accurate energies. Moreover, little is known about the error in the electron density (ρr). Non‐Covalent Interaction method (NCI) has been used to analyze π stacking from the electron density. However, for these interactions, the information that can be extracted with this method is quite limited. We compare the DFT and CCSD intermolecular ρr. The correlation between both densities is close to one, but DFT underestimates its value. To evaluate, if the strength of the π−π interaction can be qualitatively inferred from density related scalar fields, we study the correlation between these fields (ρr multiplied by the sign of the second eigenvalue of its hessian, signλ2ρ, the laplacian of ρr, ∇2ρr, the virial field, Vr, the Lagrangian, Gr, and the Hamiltonian, Kr, kinetic energy density) and the interaction energy. Surprisingly, all the scalar fields have a better correlation with the energy than signλ2ρ. This quantity is normally plotted over the reduced density gradient (RDG) isosurface in the NCI method to get an insight of intermolecular interactions, but the other scalar fields give a better picture of the energetic nature of π−π interactions. Moreover, we show that signλ2ρ cannot be used as an indicator of repulsive interactions (positive values), because for the studied π systems, the more energetic the interaction is, the more positive signλ2ρ. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 00207608 |
| DOI: | 10.1002/qua.27051 |
