Tight-binding Quantum Chemical Method Research Articles

Study on the adsorption of 2,4-dichlorophenoxyacetic acid on silver doped carbon nanotube using tight-binding quantum chemical method

The GFN2-xTB tight-binding quantum chemical method was utilized to investigate the adsorption ability of 2,4-dichlorophenoxylacetic acid (2,4-D) on pristine single-walled carbon nanotube (CNT) and silver-doped carbon nanotube (Ag-CNT). The effects of solvents (water, methanol, and acetonitrile) on the adsorption process were evaluated via the linear Poisson-Boltzmann analysis algorithm. The analysis of ionization energy, electron affinity, and global electrophilic indexes indicates that Ag doping alters the electronic properties of CNT through the formation of Ag-C chemical bonds. While the adsorption process of 2,4-D on pristine CNT is primarily of a physical nature, the adsorption on Ag-CNT involves chemical adsorption facilitated by the formation of Ag-Cl and Ag-O bonds. Contributions from non-covalent interactions (such as π-π stacking, van der Waals interactions, etc.) were analysed and clarified through the computation of the reduced density gradient. Our findings suggest that Ag-CNT has significant potential as a material for the adsorption and remediation of 2,4-D.

Understanding the interaction in cellulose–chitosan composite and its adsorption ability for Nickel (II): a theoretical investigation

ABSTRACT The tight-binding quantum chemical method (GFN2-xTB) was performed to study the nature of the interaction between the two components in a cellulose–chitosan composite (CCS) and its adsorption ability for Ni2+ and NiOH+. The interaction energy, topology of bond paths, frontier molecular orbitals, Fukui functions, and molecular electrostatic potentials were calculated and analysed to figure out the interaction between the components in the CCS. The obtained results show that cellulose and chitosan mainly interact via the formation of hydrogen bonds and van der Waals forces. The CCS shows high adsorption ability for Ni2+ and NiOH+. The preferred adsorption sites of Ni(II) on the CCS were determined and analysed. The improvement in adsorption ability of CCS over pristine cellulose and chitosan was attributed to the changes in structure and electronic properties of the material due to the interaction between the components.

Fe and Ag supported on activated carbon as an effective adsorbent for 2,4-dichlorophenoxylacetic acid treatment: a theoretical study

Extended tight-binding quantum chemical method (GFN2-xTB) was performed to investigate the adsorption of 2,4-dichlorophenoxylacetic acid (2,4-D) on activated carbon (AC) and AC modified by Fe or Ag (AC-M). Electronic properties of the studied systems were estimated via vertical ionisation potential, vertical electron affinity, and global electrophilicity index. Adsorption energy, population analysis, and geometrical parameters were calculated to clarify the adsorption ability of AC and AC-M. The results indicated that the introduction of metal atoms to AC substantially enhanced the adsorption ability for 2,4-D. The adsorption mechanism changed from physical adsorption (on AC) to chemisorption (on AC-M). The influence of different solvents (water, methanol, and acetonitrile) on the adsorption process was studied via an Analytical linearized Poisson-Boltzmann algorithm.

A theoretical study on the adsorption of dichlorodiphenyltrichloroethane (DDT) on graphitic carbon nitride (g-C3N4) and g-C3N4 modified with cluster Ni2

A robust and accurate tight-binding quantum chemical method was performed to study adsorption process of dichlorodiphenyltrichloroethane (DDT) on graphitic carbon nitride (g-C3N4) and g-C3N4 modified with nickel cluster (Ni2). The adsorption energy, charges on atoms, bond orders have been calculated and analysed. The obtained results indicate that the adsorption of DDT on the pristine g-C3N4 is physical of nature. Ni2 cluster can be easily doped on g-C3N4 due to the formation of chemical bonds. The Ni2-g-C3N4 system exhibits enhanced adsorption ability for DDT.

BODIPY-DERIVATIVES AS PHOTOSENSITIZERS IN PHOTODYNAMIC THERAPY: THE RELATIONSHIP BETWEEN ELECTRONIC PROPERTIES AND LIGHT ABSORPTION EFFICIENCY

In this study, the structural and electronic properties of BODIPY and its twelve derivates, including meso-amino, meso-alkoxy, meso-phenyl, meso-alkyl and other compounds, were investigated using an accurate and broadly parametrized self-consistent tight-binding quantum chemical method named GFN2-xTB. The influence of the substituent groups on the geometrical parameters, the HOMOLUMO gap, and electronic properties of BODIPYs was analyzed. The obtained results have shown that the presence of substituents at the R2 position did not significantly change the structural parameters of BODIPY. The electron-acceptor or electron-donor substituents in the meso-position have different effects on the electronic parameters of the molecules. A correlation between the global electrophilicity index and the HOMO-LUMO gap was found. Among the studied systems, the BODIPY-derivative with a -NO2 group at the meso-position was evaluated as the most promising candidate for photosensitizers in PDT.

Revisiting stacking interactions in tetrathiafulvalene and selected derivatives using tight-binding quantum chemical calculations and local coupled-cluster method.

The engineering of supramolecular architectures needs accurate descriptions of the intermolecular interactions in crystal structures. Tetrathiafulvalene (TTF) is an effective building block used in the construction of promising functional materials. The parallel packing of the neutral TTF-TTF system was studied previously using the high-level quantum chemical method, advancing it as a valuable model system. The recently developed tight-binding quantum chemical method GFN2-xTB and local coupled-cluster method DLPNO-CCSD(T) were used to investigate the stacking interactions of TTF and selected derivatives deposited in the Cambridge Structural Database. Using the interaction energy of the TTF-TTF dimer calculated at the CCSD(T)/CBS level as the reference, the accuracies of the two methods are investigated. The energy decomposition analysis within the DLPNO-CCSD(T) framework reveals the importance of dispersion interaction in the TTF-related stacking systems. The dispersion interaction density plot vividly shows the magnitude and distribution of the dispersion interaction, providing a revealing insight into the stacking interactions in crystal structures. The results show that the GFN2-xTB and DLPNO-CCSD(T) methods could achieve accuracy at an affordable computational cost, which would be valuable in understanding the nature of parallel stacking in supramolecular systems.

A theoretical study on the influence of non-metal (B, C, N, O, F) doping on the electronic and optical properties of graphitic carbon nitride (g-C3N4)

A robust and accurate tight-binding quantum chemical method (GFN2-xTB) was performed to study the electronic and optical properties of graphitic carbon nitride (g-C3N4) and g-C3N4 modified with non-metal atom (B, C, N, O, F). The vertical ionization potential, electron affinity and global electrophilicity indexes were calculated and analyzed. The obtained results show that the doping of B, C, N, O or F atom onto the surface g-C3N4 is favorable in terms of formation energy. The introduction of non-metal atoms raises the Lewis acidity of g-C3N4. The calculated UV-VIS spectra show that the doping of non-metal atoms increases the absorption intensity of visible light compared to the pure g-C3N4.

GFN2-xTB-An Accurate and Broadly Parametrized Self-Consistent Tight-Binding Quantum Chemical Method with Multipole Electrostatics and Density-Dependent Dispersion Contributions.

An extended semiempirical tight-binding model is presented, which is primarily designed for the fast calculation of structures and noncovalent interaction energies for molecular systems with roughly 1000 atoms. The essential novelty in this so-called GFN2-xTB method is the inclusion of anisotropic second order density fluctuation effects via short-range damped interactions of cumulative atomic multipole moments. Without noticeable increase in the computational demands, this results in a less empirical and overall more physically sound method, which does not require any classical halogen or hydrogen bonding corrections and which relies solely on global and element-specific parameters (available up to radon, Z = 86). Moreover, the atomic partial charge dependent D4 London dispersion model is incorporated self-consistently, which can be naturally obtained in a tight-binding picture from second order density fluctuations. Fully analytical and numerically precise gradients (nuclear forces) are implemented. The accuracy of the method is benchmarked for a wide variety of systems and compared with other semiempirical methods. Along with excellent performance for the "target" properties, we also find lower errors for "off-target" properties such as barrier heights and molecular dipole moments. High computational efficiency along with the improved physics compared to its precursor GFN-xTB makes this method well-suited to explore the conformational space of molecular systems. Significant improvements are furthermore observed for various benchmark sets, which are prototypical for biomolecular systems in aqueous solution.

Fast and Reasonable Geometry Optimization of Lanthanoid Complexes with an Extended Tight Binding Quantum Chemical Method.

The recently developed tight binding electronic structure approach GFN-xTB is tested in a comprehensive and diverse lanthanoid geometry optimization benchmark containing 80 lanthanoid complexes. The results are evaluated with reference to high-quality X-ray molecular structures obtained from the Cambridge Structural Database and theoretical DFT-D3(BJ) optimized structures for a few Pm (Z = 61) containing systems. The average structural heavy-atom root-mean-square deviation of GFN-xTB (0.65 Å) is smaller compared to its competitors, the Sparkle/PM6 (0.86 Å) and HF-3c (0.68 Å) quantum chemical methods. It is shown that GFN-xTB yields chemically reasonable structures, less outliers, and performs well in terms of overall computational speed compared to other low-cost methods. The good reproduction of large lanthanoid complex structures corroborates the wide applicability of the GFN-xTB approach and its value as an efficient low-cost quantum chemical method. Its main purpose is the search for energetically low-lying complex conformations in the elucidation of reaction mechanisms.

Quantum-Chemical Foundations of the Topological Substructural Molecular Design

The topological substructural molecular design (TOPS-MODE) approach is formulated as a tight-binding quantum-chemical method. The approach is based on certain postulates that permit to express any molecular property as a function of the spectral moments of certain types of molecular and environment-dependent energies. We use several empirical potentials to account for these intrinsic and external molecular energies. We prove that any molecular property expressed in terms of a quantitative structure-property and structure-activity relationships (QSPR/QSAR) model developed by using the TOPS-MODE method can be expressed as a bond additivity function. In addition, such a property can also be expressed as a substructural cluster expansion function. The conditions for such bond contributions being transferable are also analyzed here. Several new statistical-mechanical electronic functions are introduced as well as a bond-bond thermal Green's function or a propagator accounting for the electronic hopping between pairs of bonds. All these new concepts are applied to the development and application of a new QSAR model for describing the toxicity of polyhalogenated-dibenzo-1,4-dioxins. The QSAR model obtained displays a significant robustness and predictability. It permits an easy structural interpretation of the structure-activity relationship in terms of bond additivity functions, which display some resemblances with other theoretical parameters obtained from first principle quantum-chemical methods.