Understanding intermolecular interactions of large systems in ground state and excited state by using density functional based tight binding methods

Abstract

A novel energy decomposition analysis scheme, named DFTB-EDA, is proposed based on the density functional based tight binding method (DFTB/TD-DFTB), which is a semi-empirical quantum mechanical method based on KS-DFT for large-scale calculations. In DFTB-EDA, the total interaction energy is divided into three terms: frozen density, polarization and dispersion. Owing to the small cost of DFTB/TD-DFTB, DFTB-EDA is capable of analyzing intermolecular interactions in large molecular systems containing several thousand atoms with high computational efficiency. It can be used not only for ground states but also for excited states. Test calculations, involving the S66 and L7 databases, several large molecules and non-covalent bonding complexes in their lowest excited states, demonstrate the efficiency, usefulness and capabilities of DFTB-EDA. Finally, the limits of DFTB-EDA are pointed out.

Dispersion Interactions in Exciton-Localized States. Theory and Applications to π–π* and n−π* Excited States

“…The decrease in electrostatics following the n−π* transition was identified as the major factor responsible for changes in the binding strength. Similar conclusions were also drawn from density functional tight binding (DFTB) interaction energy decomposition . Although the rearrangement of the electron density is no doubt the primary effect behind the change from ground- to excited-state interactions, second-order effects in the intermolecular potential cannot be neglected .…”

“…Similar conclusions were also drawn from density functional tight binding (DFTB) interaction energy decomposition. 33 Although the rearrangement of the electron density is no doubt the primary effect behind the change from ground- to excited-state interactions, second-order effects in the intermolecular potential cannot be neglected. 34 At present, neither ALMO- nor DFTB-EDA provides a rigorous account for the second-order dispersion energy.…”

Energy decomposition analysis methods for intermolecular interactions with excited states

“…With the np* excitation, the electron in the lone pair of the N atom in pyridine is transferred to the p* orbital, leading to the loss of the capability of pyridine to form the hydrogen bond. It is noted that in the TD-DFTB-EDA results for pyridineÁ Á ÁH 2 O with the lowest excited state, 13 the value of the DE frz term, which is the combination of electrostatic and exchange-repulsion, is also positive. Analogously, according to the ALMO-EDA results shown in Table 3, with the excitation, the values of electrostatic and polarization decrease while those of the charge transfer term increases.…”

“…In 2020, DFTB-EDA was presented by the authors of this paper for intermolecular interactions both in the ground state and the excited state by using density functional based tight binding methods. 13 DFTB-EDA is able to analyze the interaction systems containing thousands of atoms. Unfortunately, this scheme cannot be expected to capture minute details of the interaction energies due to the inherent parametrization and the minimal basis set.…”

Comprehensive Study of the Chemistry behind the Stability of Carboxylic SWCNT Dispersions in the Development of a Transparent Electrode

“…Later, to understand the interactions of COOH-functionalized SWCNTs with different dispersants, DFT calculations were applied. The application of the DFTB level of theory ensured the obtaining of reliable geometries for these huge systems at a reasonable computational cost [ 25 , 26 , 27 , 28 , 29 , 30 ], while single point energy calculations via the DFT method ensured the obtaining of reliable information on noncovalent interactions [ 31 , 32 , 33 ]. Particular attention was focused on understanding how the protonation of COOH groups influenced the binding energies between the SWCNTs and selected dispersants.…”